1

CORRECTED MANUSCRIPT 20102013 1

2

A calorimetric and thermodynamic investigation of the synthetic analogues of cobaltomenite 3

CoSeO3middot2H2O and ahlfeldite NiSeO3middot2H2O 4

5

Marina V Charykova1 Vladimir G Krivovichev1 6

Maksim I Lelet2 Оxana S Yakovenko1 7

Evgeny VSuleimanov2 Wulf Depmeier3 8

Viktorina V Semenova1 and Maina L Zorina1 9

10 1Department of Geology St Petersburg State University 7ndash9 University Embankment Saint- 11

Petersburg 199034 Russia 12 2Department of Chemistry Nizhny Novgorod State UniversityNizhny 65 Ilyinskaya St Novgorod 13

603950 Russia 14 3Institut fuumlr Geowissenschaften ndash Abt Mineralogie-Kristallographie Universitaumlt Kiel 15

Olshausenstraszlige 40 D-24098 Kiel Germany 16

17 18 19

Corresponding author E-mail vkrivoviyandexcom 20

21

Abstract 22

Thermophysical and thermochemical calorimetric investigations were carried out on 23

synthetic analogs of two minerals cobaltomenite (CoSeO3middot2H2O) and ahlfeldite (NiSeO3middot2H2O) 24

The synthesis was realized by mixing of aqueous solutions of cobalt and nikel nitrates accordingly 25

and sodium selenite acidified with the help of a solution of nitric acid and characterized by XRD 26

powder diffraction and FTIR spectroscopy methods The low-temperature heat capacity of 27

CoSeO3middot2H2O and NiSeO3middot2H2O were measured using adiabatic calorimetry between 8 and 340 K 28

and the third-law entropies were determined Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 29

J(molmiddotK) and So (298 K NiSeO3middot2H2O cr) = 1729 plusmn 10 J(molmiddotK) are obtained with an 30

uncertainty of 05 The enthalpies of formation for CoSeO3middot2H2O and NiSeO3middot2H2O were 31

determined by solution calorimetry with H2SO4 solution as the solvent and giving of HΔ (298 K 32

CoSeO3middot2H2O cr) = ndash11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = ndash11333 kJmol The 33

Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can be 34

2

calculated on the basis on of HΔ and o

f SΔ of GΔ (298 K CoSeO3middot2H2O cr) = ndash9374 kJmol and 35

of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 kJmol Smoothed Cpdeg(T) values between T = 0 K and 36

T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O (cr) are presented along with values for Sdeg and 37

the functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] These results motivate a re-evaluation of the natural 38

conditions under which selenites and selenates replace selenides and sulfides in the oxidation 39

zones of sulfide ore deposits or upon weathering of technologic waste The values of ΔfGdeg for 40

CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH diagrams of the CondashSendashH2O 41

and NindashSendashH2O systems These diagrams have been constructed for the average contents of these 42

elements in acidic waters of the oxidation zones of sulfide deposits The behavior of selenium 43

cobalt and nickel in the surface environment have been quantitatively explained by variations of 44

the redox potential and the acidityndashbasicity of the mineral-forming medium Precisely these 45

parameters determine the migration ability of selenium compounds and its precipitation in the form 46

of various solid phases 47

48

Keywords сobaltomenite аhlfeldite heat capacity entropy enthalpy of formation the Gibbs 49

energy of formation 50

51

52

53

54

3

55 Introduction 56

57 Since the discovery of the toxic properties and biological significance of selenium there have 58

been continuous studies of the geological occurrence and geochemistry of this element in 59

oxygenated aqueous environments Drainage from mineralized and mined areas may have high 60

concentrations of dissolved selenium and this is of major concern as waterflows soils and plants in 61

the vicinity of ore bodies containing Se-bearing sulfides and selenides are prone to be the low-62

temperature oxidizing environments for the natural sources of Se (Treatise on Geochemistry 2004) 63

Most selenites are formed by chemical weathering of ores by oxygenated waters establishing 64

conditions of increased Eh and low or neutral pH (with seasonal fluctuations of temperatures and 65

atmospheric pressure) These parameters define the migration of selenium and its precipitation in 66

the form of selenite minerals (chalcomenite СuSeO3middot2H2O cobaltomenite CoSeO3middot2H2O ahlfeldite 67

NiSeO3middot2H2O mandarinoite Fe2(SeO3)3middot6H2O molybdomenite PbSeO3) EhndashpH diagrams of the 68

MendashSendashH2O systems (Me = Co Ni Fe Cu Zn Pb) have been published which make it possible to 69

estimate the conditions for the near-surface formation of Se minerals (selenites) (Krivovichev et al 70

2011) 71

The analysis of the thermodynamic data for calculation of mineral equilibria involving 72

selenites and selenates of Fe Cu Zn Pb Co and Ni (Seby et al 2001 Olin et al 2005 Charykova 73

et al 2010) showed that even in cases when it is possible to find corresponding parameters in the 74

literature they frequently raise questions and need specification In particular this is true for the 75

standard thermodynamic functions of ahlfeldite NiSeO3middot2H2O and cobaltomenite CoSeO3middot2H2O 76

Their standard enthalpies were determined by Selivanova et al (1963 1964) and then with use of 77

data from Thukhlantsev and Tomashevsky (1957) the standard entropy and Gibbs energy of their 78

formation were calculated These experimental data have been used for the calculation of standard 79

thermodynamic functions of ahlfeldite and cobaltomenite cited in many reference books and data 80

bases (Vlaev et al 2005) 81

Ahlfeldite and cobaltomenite are rare minerals which are formed only in the oxidation zone of 82

sulfide- and selenide-bearing ores in the deposits Serro-de-Kacheuta (Argentina) Pahakake Dragon 83

(Bolivia) Muzoni (Zaire) and some hydrothermal deposits in the State of Utah (USA) The 84

experimental determination of thermodynamic data of rare minerals in general and of the title 85

compounds in particular on the basis of studying their solubility or by calorimetric measurements 86

can hardly rely on natural samples because they usually do not occur in sufficient amounts form 87

only tiny crystals may include inclusions be covered by weathering crusts and almost inevitably 88

contain impurities All these defects influence many properties of the samples studied and certainly 89

their thermodynamic parameters In this communication we therefore present the results of our 90

4

investigations of the enthalpy of formation and of the heat capacity of synthetic analogues of 91

cobaltomenite and ahlfeldite 92

93 Experimental methods 94

Sample preparation 95

For the synthesis of cobalt and nickel selenites we have used a modification of a technique 96

proposed in Vlaev et al (2005 2006) The synthesis was realized by boiling-dry of aqueous 97

solutions of cobalt and nickel nitrates respectively and sodium selenite acidified with a solution of 98

nitric acid To the warm (50оС) 02N solution of nickel or cobalt salts (pH 52-53) a 02N solution 99

of Na2SeO3 (pH 60-62) was added slowly and dropwise After heating for 2-3 hours and hashing 100

for a weak solution with the residue have been left to ripen at room temperature for 20 days after 101

which the formed precipitate was separated by decantation washed with distilled water and dried at 102

room temperature 103

The phase purity of the synthetic products was characterized using an XRD powder 104

diffractometer (Rigaku Miniflex II) and a FTIR spectrometer BRUKER VERTEX 80 Its 105

composition was determined using X-ray fluorescence (dual-beam system operating with a 106

scanning focused ion beam and a scanning electron beam Quanta 200 3D FEI) In addition the 107

concentrations of Co Ni Se in the synthesized phases were determined (after their full dissolution 108

in acidic solutions) by means of method ICP MS (mass spectrometer ELAN-DRC-e PERKIN 109

ELMER) 110

Calorimetric methods 111

The enthalpies of formation for CoSeO3middot2H2O and NiSeO3middot2H2O were determined using 112

solution calorimetry with H2SO4 solution as the solvent The heat of solution was measured using a 113

differential heat-conducting Tian-Calvet calorimeter Calvet 20 (Lelet et al 2011) T = 298 K 114

Dissolution experiments were performed in a Teflon container holding a smaller inner-Teflon 115

vessel The inner vessel contained the sample to be dissolved and the external container the solvent 116

consisting of 3 M sulfuric acid Further details on the construction of the calorimeter and the 117

experimental procedures are given in Lelet et al (2011) 118

The low-temperature heat capacities of CoSeO3middot2H2O and NiSeO3middot2H2O was determined 119

using adiabatic calorimetry from T = 8 to 340 K Measurements were done using a lsquolsquoAK-902BCT-120

21rdquo calorimeter (Termax Russia) The experimental precision was determined from the heat 121

capacity measurements on synthetic corundum (mass fraction purity 099999) and benzoic acid 122

(mass fraction purity 099998) The results show that with this calorimeter and the set-up used 123

Cpo(T) can be determined with a experimental precision of plusmn2 from T = 4 to 15 K plusmn05 at T = 124

5

15 to 40 K and plusmn02 in the interval T = 40 to 340 K The Срdeg results between 6 K and 300 K on 125

benzoic acid relative to standard values (Gatta et al 2006) are shown in Fig 1 The agreement is 126

better than plusmn02 at T gt 20 K and better than plusmn18 at T lt 20 K 127

For the Cpo determination of CoSeO3middot2H2O and NiSeO3middot2H2O 05271 and 07227 g of the 128

samples were used Liquid nitrogen and helium were used to obtain cryogenic temperatures in two 129

different sets of measurements One set of data was collected between T = (80 and 350) K and the 130

other from T = 6 to 80 K An evacuated ampoule containing a pellet of CoSeO3middot2H2O or 131

NiSeO3middot2H2O was filled with dry helium to serve as a heat exchanger (room temperature and 132

pressure 8 kPa) The ampoule was closed and hermetically sealed using indium Further details on 133

the construction of the calorimeter and the experimental procedures are given in (Varushchenko et 134

al 1997) 135

136

Results 137

Sample characterization 138

The obtained substances were in the form of small columnar pink-violet (cobalt selenite) or 139

green (nickel selenite) crystals of up to 10 μm in length and 05-2 μm wide The X-ray powder 140

diffraction data are shown in Fig 2 The interplanar distances and the relative intensities of the peaks 141

were derived by profile fitting using PDXL (version 2) software They are in excellent agreement with 142

data reported in PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-009-364 (for ahfeldite) The unit 143

cell parameters calculated from the powder data (table 1) are in good accordance with data obtained 144

by other authors (Wildner 1990 Vlaev et al 2005 2006) The X-ray fluorescence results gave a 145

CoSe ratio of 100102 and NiSe ratio of 100101 The amount of other elements was below the 146

detection limit which is approximately 0003 wt for all elements in the periodic chart from 147

sodium to uranium The infrared spectra are similar to those obtained by other authors (table 2) The 148

combined use of these methods show that the synthetic products are single-phased have the 149

chemical composition CoSeO3middot2H2O or NiSeO3middot2H2O 150

Thus the synthetic hydrous cobalt and nickel selenites correspond in structure and 151

spectroscopic features to the natural cobaltomenite and ahlfeldite and may be used to determine its 152

properties in particular the thermodynamic parameters 153

154

Enthalpy of formation 155 The determination of the standard enthalpy of formation o

f HΔ (298 K) for AIISeO3middot2H2O 156

(AII=Co Ni) was performed using H2SO4-solution calorimetry In order to do so the enthalpy of 157

solution at T = 298 K was determined for each of the following phases 158

Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1) (1) 159

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

2

calculated on the basis on of HΔ and o

f SΔ of GΔ (298 K CoSeO3middot2H2O cr) = ndash9374 kJmol and 35

of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 kJmol Smoothed Cpdeg(T) values between T = 0 K and 36

T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O (cr) are presented along with values for Sdeg and 37

the functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] These results motivate a re-evaluation of the natural 38

conditions under which selenites and selenates replace selenides and sulfides in the oxidation 39

zones of sulfide ore deposits or upon weathering of technologic waste The values of ΔfGdeg for 40

CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH diagrams of the CondashSendashH2O 41

and NindashSendashH2O systems These diagrams have been constructed for the average contents of these 42

elements in acidic waters of the oxidation zones of sulfide deposits The behavior of selenium 43

cobalt and nickel in the surface environment have been quantitatively explained by variations of 44

the redox potential and the acidityndashbasicity of the mineral-forming medium Precisely these 45

parameters determine the migration ability of selenium compounds and its precipitation in the form 46

of various solid phases 47

48

Keywords сobaltomenite аhlfeldite heat capacity entropy enthalpy of formation the Gibbs 49

energy of formation 50

51

52

53

54

3

55 Introduction 56

57 Since the discovery of the toxic properties and biological significance of selenium there have 58

been continuous studies of the geological occurrence and geochemistry of this element in 59

oxygenated aqueous environments Drainage from mineralized and mined areas may have high 60

concentrations of dissolved selenium and this is of major concern as waterflows soils and plants in 61

the vicinity of ore bodies containing Se-bearing sulfides and selenides are prone to be the low-62

temperature oxidizing environments for the natural sources of Se (Treatise on Geochemistry 2004) 63

Most selenites are formed by chemical weathering of ores by oxygenated waters establishing 64

conditions of increased Eh and low or neutral pH (with seasonal fluctuations of temperatures and 65

atmospheric pressure) These parameters define the migration of selenium and its precipitation in 66

the form of selenite minerals (chalcomenite СuSeO3middot2H2O cobaltomenite CoSeO3middot2H2O ahlfeldite 67

NiSeO3middot2H2O mandarinoite Fe2(SeO3)3middot6H2O molybdomenite PbSeO3) EhndashpH diagrams of the 68

MendashSendashH2O systems (Me = Co Ni Fe Cu Zn Pb) have been published which make it possible to 69

estimate the conditions for the near-surface formation of Se minerals (selenites) (Krivovichev et al 70

2011) 71

The analysis of the thermodynamic data for calculation of mineral equilibria involving 72

selenites and selenates of Fe Cu Zn Pb Co and Ni (Seby et al 2001 Olin et al 2005 Charykova 73

et al 2010) showed that even in cases when it is possible to find corresponding parameters in the 74

literature they frequently raise questions and need specification In particular this is true for the 75

standard thermodynamic functions of ahlfeldite NiSeO3middot2H2O and cobaltomenite CoSeO3middot2H2O 76

Their standard enthalpies were determined by Selivanova et al (1963 1964) and then with use of 77

data from Thukhlantsev and Tomashevsky (1957) the standard entropy and Gibbs energy of their 78

formation were calculated These experimental data have been used for the calculation of standard 79

thermodynamic functions of ahlfeldite and cobaltomenite cited in many reference books and data 80

bases (Vlaev et al 2005) 81

Ahlfeldite and cobaltomenite are rare minerals which are formed only in the oxidation zone of 82

sulfide- and selenide-bearing ores in the deposits Serro-de-Kacheuta (Argentina) Pahakake Dragon 83

(Bolivia) Muzoni (Zaire) and some hydrothermal deposits in the State of Utah (USA) The 84

experimental determination of thermodynamic data of rare minerals in general and of the title 85

compounds in particular on the basis of studying their solubility or by calorimetric measurements 86

can hardly rely on natural samples because they usually do not occur in sufficient amounts form 87

only tiny crystals may include inclusions be covered by weathering crusts and almost inevitably 88

contain impurities All these defects influence many properties of the samples studied and certainly 89

their thermodynamic parameters In this communication we therefore present the results of our 90

4

investigations of the enthalpy of formation and of the heat capacity of synthetic analogues of 91

cobaltomenite and ahlfeldite 92

93 Experimental methods 94

Sample preparation 95

For the synthesis of cobalt and nickel selenites we have used a modification of a technique 96

proposed in Vlaev et al (2005 2006) The synthesis was realized by boiling-dry of aqueous 97

solutions of cobalt and nickel nitrates respectively and sodium selenite acidified with a solution of 98

nitric acid To the warm (50оС) 02N solution of nickel or cobalt salts (pH 52-53) a 02N solution 99

of Na2SeO3 (pH 60-62) was added slowly and dropwise After heating for 2-3 hours and hashing 100

for a weak solution with the residue have been left to ripen at room temperature for 20 days after 101

which the formed precipitate was separated by decantation washed with distilled water and dried at 102

room temperature 103

The phase purity of the synthetic products was characterized using an XRD powder 104

diffractometer (Rigaku Miniflex II) and a FTIR spectrometer BRUKER VERTEX 80 Its 105

composition was determined using X-ray fluorescence (dual-beam system operating with a 106

scanning focused ion beam and a scanning electron beam Quanta 200 3D FEI) In addition the 107

concentrations of Co Ni Se in the synthesized phases were determined (after their full dissolution 108

in acidic solutions) by means of method ICP MS (mass spectrometer ELAN-DRC-e PERKIN 109

ELMER) 110

Calorimetric methods 111

The enthalpies of formation for CoSeO3middot2H2O and NiSeO3middot2H2O were determined using 112

solution calorimetry with H2SO4 solution as the solvent The heat of solution was measured using a 113

differential heat-conducting Tian-Calvet calorimeter Calvet 20 (Lelet et al 2011) T = 298 K 114

Dissolution experiments were performed in a Teflon container holding a smaller inner-Teflon 115

vessel The inner vessel contained the sample to be dissolved and the external container the solvent 116

consisting of 3 M sulfuric acid Further details on the construction of the calorimeter and the 117

experimental procedures are given in Lelet et al (2011) 118

The low-temperature heat capacities of CoSeO3middot2H2O and NiSeO3middot2H2O was determined 119

using adiabatic calorimetry from T = 8 to 340 K Measurements were done using a lsquolsquoAK-902BCT-120

21rdquo calorimeter (Termax Russia) The experimental precision was determined from the heat 121

capacity measurements on synthetic corundum (mass fraction purity 099999) and benzoic acid 122

(mass fraction purity 099998) The results show that with this calorimeter and the set-up used 123

Cpo(T) can be determined with a experimental precision of plusmn2 from T = 4 to 15 K plusmn05 at T = 124

5

15 to 40 K and plusmn02 in the interval T = 40 to 340 K The Срdeg results between 6 K and 300 K on 125

benzoic acid relative to standard values (Gatta et al 2006) are shown in Fig 1 The agreement is 126

better than plusmn02 at T gt 20 K and better than plusmn18 at T lt 20 K 127

For the Cpo determination of CoSeO3middot2H2O and NiSeO3middot2H2O 05271 and 07227 g of the 128

samples were used Liquid nitrogen and helium were used to obtain cryogenic temperatures in two 129

different sets of measurements One set of data was collected between T = (80 and 350) K and the 130

other from T = 6 to 80 K An evacuated ampoule containing a pellet of CoSeO3middot2H2O or 131

NiSeO3middot2H2O was filled with dry helium to serve as a heat exchanger (room temperature and 132

pressure 8 kPa) The ampoule was closed and hermetically sealed using indium Further details on 133

the construction of the calorimeter and the experimental procedures are given in (Varushchenko et 134

al 1997) 135

136

Results 137

Sample characterization 138

The obtained substances were in the form of small columnar pink-violet (cobalt selenite) or 139

green (nickel selenite) crystals of up to 10 μm in length and 05-2 μm wide The X-ray powder 140

diffraction data are shown in Fig 2 The interplanar distances and the relative intensities of the peaks 141

were derived by profile fitting using PDXL (version 2) software They are in excellent agreement with 142

data reported in PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-009-364 (for ahfeldite) The unit 143

cell parameters calculated from the powder data (table 1) are in good accordance with data obtained 144

by other authors (Wildner 1990 Vlaev et al 2005 2006) The X-ray fluorescence results gave a 145

CoSe ratio of 100102 and NiSe ratio of 100101 The amount of other elements was below the 146

detection limit which is approximately 0003 wt for all elements in the periodic chart from 147

sodium to uranium The infrared spectra are similar to those obtained by other authors (table 2) The 148

combined use of these methods show that the synthetic products are single-phased have the 149

chemical composition CoSeO3middot2H2O or NiSeO3middot2H2O 150

Thus the synthetic hydrous cobalt and nickel selenites correspond in structure and 151

spectroscopic features to the natural cobaltomenite and ahlfeldite and may be used to determine its 152

properties in particular the thermodynamic parameters 153

154

Enthalpy of formation 155 The determination of the standard enthalpy of formation o

f HΔ (298 K) for AIISeO3middot2H2O 156

(AII=Co Ni) was performed using H2SO4-solution calorimetry In order to do so the enthalpy of 157

solution at T = 298 K was determined for each of the following phases 158

Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1) (1) 159

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

3

55 Introduction 56

57 Since the discovery of the toxic properties and biological significance of selenium there have 58

been continuous studies of the geological occurrence and geochemistry of this element in 59

oxygenated aqueous environments Drainage from mineralized and mined areas may have high 60

concentrations of dissolved selenium and this is of major concern as waterflows soils and plants in 61

the vicinity of ore bodies containing Se-bearing sulfides and selenides are prone to be the low-62

temperature oxidizing environments for the natural sources of Se (Treatise on Geochemistry 2004) 63

Most selenites are formed by chemical weathering of ores by oxygenated waters establishing 64

conditions of increased Eh and low or neutral pH (with seasonal fluctuations of temperatures and 65

atmospheric pressure) These parameters define the migration of selenium and its precipitation in 66

the form of selenite minerals (chalcomenite СuSeO3middot2H2O cobaltomenite CoSeO3middot2H2O ahlfeldite 67

NiSeO3middot2H2O mandarinoite Fe2(SeO3)3middot6H2O molybdomenite PbSeO3) EhndashpH diagrams of the 68

MendashSendashH2O systems (Me = Co Ni Fe Cu Zn Pb) have been published which make it possible to 69

estimate the conditions for the near-surface formation of Se minerals (selenites) (Krivovichev et al 70

2011) 71

The analysis of the thermodynamic data for calculation of mineral equilibria involving 72

selenites and selenates of Fe Cu Zn Pb Co and Ni (Seby et al 2001 Olin et al 2005 Charykova 73

et al 2010) showed that even in cases when it is possible to find corresponding parameters in the 74

literature they frequently raise questions and need specification In particular this is true for the 75

standard thermodynamic functions of ahlfeldite NiSeO3middot2H2O and cobaltomenite CoSeO3middot2H2O 76

Their standard enthalpies were determined by Selivanova et al (1963 1964) and then with use of 77

data from Thukhlantsev and Tomashevsky (1957) the standard entropy and Gibbs energy of their 78

formation were calculated These experimental data have been used for the calculation of standard 79

thermodynamic functions of ahlfeldite and cobaltomenite cited in many reference books and data 80

bases (Vlaev et al 2005) 81

Ahlfeldite and cobaltomenite are rare minerals which are formed only in the oxidation zone of 82

sulfide- and selenide-bearing ores in the deposits Serro-de-Kacheuta (Argentina) Pahakake Dragon 83

(Bolivia) Muzoni (Zaire) and some hydrothermal deposits in the State of Utah (USA) The 84

experimental determination of thermodynamic data of rare minerals in general and of the title 85

compounds in particular on the basis of studying their solubility or by calorimetric measurements 86

can hardly rely on natural samples because they usually do not occur in sufficient amounts form 87

only tiny crystals may include inclusions be covered by weathering crusts and almost inevitably 88

contain impurities All these defects influence many properties of the samples studied and certainly 89

their thermodynamic parameters In this communication we therefore present the results of our 90

4

investigations of the enthalpy of formation and of the heat capacity of synthetic analogues of 91

cobaltomenite and ahlfeldite 92

93 Experimental methods 94

Sample preparation 95

For the synthesis of cobalt and nickel selenites we have used a modification of a technique 96

proposed in Vlaev et al (2005 2006) The synthesis was realized by boiling-dry of aqueous 97

solutions of cobalt and nickel nitrates respectively and sodium selenite acidified with a solution of 98

nitric acid To the warm (50оС) 02N solution of nickel or cobalt salts (pH 52-53) a 02N solution 99

of Na2SeO3 (pH 60-62) was added slowly and dropwise After heating for 2-3 hours and hashing 100

for a weak solution with the residue have been left to ripen at room temperature for 20 days after 101

which the formed precipitate was separated by decantation washed with distilled water and dried at 102

room temperature 103

The phase purity of the synthetic products was characterized using an XRD powder 104

diffractometer (Rigaku Miniflex II) and a FTIR spectrometer BRUKER VERTEX 80 Its 105

composition was determined using X-ray fluorescence (dual-beam system operating with a 106

scanning focused ion beam and a scanning electron beam Quanta 200 3D FEI) In addition the 107

concentrations of Co Ni Se in the synthesized phases were determined (after their full dissolution 108

in acidic solutions) by means of method ICP MS (mass spectrometer ELAN-DRC-e PERKIN 109

ELMER) 110

Calorimetric methods 111

The enthalpies of formation for CoSeO3middot2H2O and NiSeO3middot2H2O were determined using 112

solution calorimetry with H2SO4 solution as the solvent The heat of solution was measured using a 113

differential heat-conducting Tian-Calvet calorimeter Calvet 20 (Lelet et al 2011) T = 298 K 114

Dissolution experiments were performed in a Teflon container holding a smaller inner-Teflon 115

vessel The inner vessel contained the sample to be dissolved and the external container the solvent 116

consisting of 3 M sulfuric acid Further details on the construction of the calorimeter and the 117

experimental procedures are given in Lelet et al (2011) 118

The low-temperature heat capacities of CoSeO3middot2H2O and NiSeO3middot2H2O was determined 119

using adiabatic calorimetry from T = 8 to 340 K Measurements were done using a lsquolsquoAK-902BCT-120

21rdquo calorimeter (Termax Russia) The experimental precision was determined from the heat 121

capacity measurements on synthetic corundum (mass fraction purity 099999) and benzoic acid 122

(mass fraction purity 099998) The results show that with this calorimeter and the set-up used 123

Cpo(T) can be determined with a experimental precision of plusmn2 from T = 4 to 15 K plusmn05 at T = 124

5

15 to 40 K and plusmn02 in the interval T = 40 to 340 K The Срdeg results between 6 K and 300 K on 125

benzoic acid relative to standard values (Gatta et al 2006) are shown in Fig 1 The agreement is 126

better than plusmn02 at T gt 20 K and better than plusmn18 at T lt 20 K 127

For the Cpo determination of CoSeO3middot2H2O and NiSeO3middot2H2O 05271 and 07227 g of the 128

samples were used Liquid nitrogen and helium were used to obtain cryogenic temperatures in two 129

different sets of measurements One set of data was collected between T = (80 and 350) K and the 130

other from T = 6 to 80 K An evacuated ampoule containing a pellet of CoSeO3middot2H2O or 131

NiSeO3middot2H2O was filled with dry helium to serve as a heat exchanger (room temperature and 132

pressure 8 kPa) The ampoule was closed and hermetically sealed using indium Further details on 133

the construction of the calorimeter and the experimental procedures are given in (Varushchenko et 134

al 1997) 135

136

Results 137

Sample characterization 138

The obtained substances were in the form of small columnar pink-violet (cobalt selenite) or 139

green (nickel selenite) crystals of up to 10 μm in length and 05-2 μm wide The X-ray powder 140

diffraction data are shown in Fig 2 The interplanar distances and the relative intensities of the peaks 141

were derived by profile fitting using PDXL (version 2) software They are in excellent agreement with 142

data reported in PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-009-364 (for ahfeldite) The unit 143

cell parameters calculated from the powder data (table 1) are in good accordance with data obtained 144

by other authors (Wildner 1990 Vlaev et al 2005 2006) The X-ray fluorescence results gave a 145

CoSe ratio of 100102 and NiSe ratio of 100101 The amount of other elements was below the 146

detection limit which is approximately 0003 wt for all elements in the periodic chart from 147

sodium to uranium The infrared spectra are similar to those obtained by other authors (table 2) The 148

combined use of these methods show that the synthetic products are single-phased have the 149

chemical composition CoSeO3middot2H2O or NiSeO3middot2H2O 150

Thus the synthetic hydrous cobalt and nickel selenites correspond in structure and 151

spectroscopic features to the natural cobaltomenite and ahlfeldite and may be used to determine its 152

properties in particular the thermodynamic parameters 153

154

Enthalpy of formation 155 The determination of the standard enthalpy of formation o

f HΔ (298 K) for AIISeO3middot2H2O 156

(AII=Co Ni) was performed using H2SO4-solution calorimetry In order to do so the enthalpy of 157

solution at T = 298 K was determined for each of the following phases 158

Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1) (1) 159

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

4

investigations of the enthalpy of formation and of the heat capacity of synthetic analogues of 91

cobaltomenite and ahlfeldite 92

93 Experimental methods 94

Sample preparation 95

For the synthesis of cobalt and nickel selenites we have used a modification of a technique 96

proposed in Vlaev et al (2005 2006) The synthesis was realized by boiling-dry of aqueous 97

solutions of cobalt and nickel nitrates respectively and sodium selenite acidified with a solution of 98

nitric acid To the warm (50оС) 02N solution of nickel or cobalt salts (pH 52-53) a 02N solution 99

of Na2SeO3 (pH 60-62) was added slowly and dropwise After heating for 2-3 hours and hashing 100

for a weak solution with the residue have been left to ripen at room temperature for 20 days after 101

which the formed precipitate was separated by decantation washed with distilled water and dried at 102

room temperature 103

The phase purity of the synthetic products was characterized using an XRD powder 104

diffractometer (Rigaku Miniflex II) and a FTIR spectrometer BRUKER VERTEX 80 Its 105

composition was determined using X-ray fluorescence (dual-beam system operating with a 106

scanning focused ion beam and a scanning electron beam Quanta 200 3D FEI) In addition the 107

concentrations of Co Ni Se in the synthesized phases were determined (after their full dissolution 108

in acidic solutions) by means of method ICP MS (mass spectrometer ELAN-DRC-e PERKIN 109

ELMER) 110

Calorimetric methods 111

The enthalpies of formation for CoSeO3middot2H2O and NiSeO3middot2H2O were determined using 112

solution calorimetry with H2SO4 solution as the solvent The heat of solution was measured using a 113

differential heat-conducting Tian-Calvet calorimeter Calvet 20 (Lelet et al 2011) T = 298 K 114

Dissolution experiments were performed in a Teflon container holding a smaller inner-Teflon 115

vessel The inner vessel contained the sample to be dissolved and the external container the solvent 116

consisting of 3 M sulfuric acid Further details on the construction of the calorimeter and the 117

experimental procedures are given in Lelet et al (2011) 118

The low-temperature heat capacities of CoSeO3middot2H2O and NiSeO3middot2H2O was determined 119

using adiabatic calorimetry from T = 8 to 340 K Measurements were done using a lsquolsquoAK-902BCT-120

21rdquo calorimeter (Termax Russia) The experimental precision was determined from the heat 121

capacity measurements on synthetic corundum (mass fraction purity 099999) and benzoic acid 122

(mass fraction purity 099998) The results show that with this calorimeter and the set-up used 123

Cpo(T) can be determined with a experimental precision of plusmn2 from T = 4 to 15 K plusmn05 at T = 124

5

15 to 40 K and plusmn02 in the interval T = 40 to 340 K The Срdeg results between 6 K and 300 K on 125

benzoic acid relative to standard values (Gatta et al 2006) are shown in Fig 1 The agreement is 126

better than plusmn02 at T gt 20 K and better than plusmn18 at T lt 20 K 127

For the Cpo determination of CoSeO3middot2H2O and NiSeO3middot2H2O 05271 and 07227 g of the 128

samples were used Liquid nitrogen and helium were used to obtain cryogenic temperatures in two 129

different sets of measurements One set of data was collected between T = (80 and 350) K and the 130

other from T = 6 to 80 K An evacuated ampoule containing a pellet of CoSeO3middot2H2O or 131

NiSeO3middot2H2O was filled with dry helium to serve as a heat exchanger (room temperature and 132

pressure 8 kPa) The ampoule was closed and hermetically sealed using indium Further details on 133

the construction of the calorimeter and the experimental procedures are given in (Varushchenko et 134

al 1997) 135

136

Results 137

Sample characterization 138

The obtained substances were in the form of small columnar pink-violet (cobalt selenite) or 139

green (nickel selenite) crystals of up to 10 μm in length and 05-2 μm wide The X-ray powder 140

diffraction data are shown in Fig 2 The interplanar distances and the relative intensities of the peaks 141

were derived by profile fitting using PDXL (version 2) software They are in excellent agreement with 142

data reported in PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-009-364 (for ahfeldite) The unit 143

cell parameters calculated from the powder data (table 1) are in good accordance with data obtained 144

by other authors (Wildner 1990 Vlaev et al 2005 2006) The X-ray fluorescence results gave a 145

CoSe ratio of 100102 and NiSe ratio of 100101 The amount of other elements was below the 146

detection limit which is approximately 0003 wt for all elements in the periodic chart from 147

sodium to uranium The infrared spectra are similar to those obtained by other authors (table 2) The 148

combined use of these methods show that the synthetic products are single-phased have the 149

chemical composition CoSeO3middot2H2O or NiSeO3middot2H2O 150

Thus the synthetic hydrous cobalt and nickel selenites correspond in structure and 151

spectroscopic features to the natural cobaltomenite and ahlfeldite and may be used to determine its 152

properties in particular the thermodynamic parameters 153

154

Enthalpy of formation 155 The determination of the standard enthalpy of formation o

f HΔ (298 K) for AIISeO3middot2H2O 156

(AII=Co Ni) was performed using H2SO4-solution calorimetry In order to do so the enthalpy of 157

solution at T = 298 K was determined for each of the following phases 158

Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1) (1) 159

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

5

15 to 40 K and plusmn02 in the interval T = 40 to 340 K The Срdeg results between 6 K and 300 K on 125

benzoic acid relative to standard values (Gatta et al 2006) are shown in Fig 1 The agreement is 126

better than plusmn02 at T gt 20 K and better than plusmn18 at T lt 20 K 127

For the Cpo determination of CoSeO3middot2H2O and NiSeO3middot2H2O 05271 and 07227 g of the 128

samples were used Liquid nitrogen and helium were used to obtain cryogenic temperatures in two 129

different sets of measurements One set of data was collected between T = (80 and 350) K and the 130

other from T = 6 to 80 K An evacuated ampoule containing a pellet of CoSeO3middot2H2O or 131

NiSeO3middot2H2O was filled with dry helium to serve as a heat exchanger (room temperature and 132

pressure 8 kPa) The ampoule was closed and hermetically sealed using indium Further details on 133

the construction of the calorimeter and the experimental procedures are given in (Varushchenko et 134

al 1997) 135

136

Results 137

Sample characterization 138

The obtained substances were in the form of small columnar pink-violet (cobalt selenite) or 139

green (nickel selenite) crystals of up to 10 μm in length and 05-2 μm wide The X-ray powder 140

diffraction data are shown in Fig 2 The interplanar distances and the relative intensities of the peaks 141

were derived by profile fitting using PDXL (version 2) software They are in excellent agreement with 142

data reported in PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-009-364 (for ahfeldite) The unit 143

cell parameters calculated from the powder data (table 1) are in good accordance with data obtained 144

by other authors (Wildner 1990 Vlaev et al 2005 2006) The X-ray fluorescence results gave a 145

CoSe ratio of 100102 and NiSe ratio of 100101 The amount of other elements was below the 146

detection limit which is approximately 0003 wt for all elements in the periodic chart from 147

sodium to uranium The infrared spectra are similar to those obtained by other authors (table 2) The 148

combined use of these methods show that the synthetic products are single-phased have the 149

chemical composition CoSeO3middot2H2O or NiSeO3middot2H2O 150

Thus the synthetic hydrous cobalt and nickel selenites correspond in structure and 151

spectroscopic features to the natural cobaltomenite and ahlfeldite and may be used to determine its 152

properties in particular the thermodynamic parameters 153

154

Enthalpy of formation 155 The determination of the standard enthalpy of formation o

f HΔ (298 K) for AIISeO3middot2H2O 156

(AII=Co Ni) was performed using H2SO4-solution calorimetry In order to do so the enthalpy of 157

solution at T = 298 K was determined for each of the following phases 158

Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1) (1) 159

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

6

AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2) (2) 160

5H2O(l) + (H2SO4 solution) rarr (solution В1) (3) 161

Na2SO4(cr) + (solution В1) rarr (solution В2) (4) 162

AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3) (5) 163

The respective values are given in table 3 Writing the reaction 164

CoSO4middot7H2O(cr) + Na2SeO3(cr) rarr CoSeO3middot2H2O(cr) + Na2SO4(cr) + 5H2O(l) (6) 165

and following Hessrsquo law one obtains 166 o

rH7Δ (298) = or H 2Δ (298) + o

rH 3Δ (298) ndash or H 4Δ (298) ndash o

rH5Δ (298) ndash or H6Δ (298)6 1 2 3 4 5 (7)

167 And 168

of HΔ (298 K AIISeO3middot2H2O cr) = o

r H7Δ (298) + of HΔ (298 K AIISO4middot7H2O cr) + 169

of HΔ (298 K Na2SeO3 cr) ndash o

f HΔ (298 K Na2SO4 cr) ndash 5 of HΔ (298 K H2O l) (8) 170

171 From the experimental results in table 3 and from literature data (Wagman et al 1982) namely 172

of HΔ (298 K CoSO4middot7H2O cr) = -297993 kJmol o

f HΔ (298 K NiSO4middot7H2O cr) = -297633 173

kJmol of HΔ (298 K Na2SeO3 cr) = -9586 kJmol o

f HΔ (298 K Na2SO4 cr) = -138708 174

kJmol of HΔ (298 K H2O l) = -285830 kJmol one obtains o

f HΔ (298 K CoSeO3middot2H2O cr) = -175

11353 kJmol of HΔ (298 K NiSeO3middot2H2O cr) = -11333 kJmol 176

177 Heat-capacity behaviour 178

The raw low-temperature Cpo data for CoSeO3middot2H2O and NiSeO3middot2H2O from both 179

measurement series are given in tables 6 and 7 Fig 3 shows a plot of the data No obvious 180

anomalies or phase transitions were observed In order to extrapolate the heat-capacity down to T = 181

0 K we used the equation nTA sdot=opC where A and n are fit parameters that were determined using 182

experimental values between T = 870 and 1175 for CoSeO3middot2H2O and T = 918 and 1485 for 183

NiSeO3middot2H2O In logarithmic form one obtains =sdotsdot minusminus 11op KmolJlnC 08041middotln(TK) ndash 16023 with 184

a correlation coefficient of Rsup2 = 09935 for CoSeO3middot2H2O and =sdotsdot minusminus 11op KmolJlnC 20596middotln(TK) 185

ndash 48225 with a correlation coefficient of Rsup2 = 09838 for NiSeO3middot2H2O In standard notation one 186

has =opC 02014middotT 08041 for CoSeO3middot2H2O and =o

pC 000805middotT 20596 for NiSeO3middot2H2O 187

The opC data were fit with the polynomial (Dachs and Geiger 2006 Suleimanov et al 2010) 188

++++=sdotsdot minusminusminusminusminus 503

22

310

11op )K()K()K(KmolJC TkTkTkk 189

36

254 )K()K()K( TkTkTk ++ (9) 190

Three separate temperature regions (from 81 to 15 K 15 to 47 K and 47 to 328 K for 191

CoSeO3middot2H2O from 92 to 16 K 16 to 50 K and 50 to 340 K for NiSeO3middot2H2O) were fit using 192

nonlinear least-squares methods The final least-squares best-fit values of the various k terms are 193

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

7

given in table 6 Fig 4 shows the difference between experimental opC p values and fitted o

pC 194

values Deviations are not more than 04 at T gt 100 K and less than 56 at T lt 100 K for 195

CoSeO3middot2H2O and 05 at T gt 100 K and less than 83 at T lt 100 K for NiSeO3middot2H2O 196

Discussion 197

The standard third-law entropy So at T = 29815 K was determined by solving the integral 198

int=29815K

K0

o )( dTTCS p (10) 199

Values of So(298 K CoSeO3middot2H2O cr) = 1832 plusmn 10 J(molmiddotK) and So(298 K NiSeO3middot2H2O cr) 200

= 1729 plusmn 10 J(molmiddotK) were obtained with an uncertainty of plusmn05 201

For the calculation of the entropy of formation of SΔ of CoSeO3middot2H2O and NiSeO3middot2H2O the 202

experimentally measured third-law entropy So together with data from the literature were used by 203

Dachs and Geiger (2006) that is So(298 K Co cr) = 3004 J(molmiddotK) So(298 K Ni cr) = 2987 204

J(molmiddotK) So(298 K Se cr) = 42442 J(molmiddotK) So(298 K O2 gas) = 205138 J(molmiddotK) So(298 205

K H2 gas) = 130684 J(molmiddotK) One obtains of SΔ (298 K CoSeO3middot2H2O cr) = ndash(6635 plusmn 10) 206

J(molmiddotK) and of SΔ (298 K NiSeO3middot2H2O cr) = ndash(6736 plusmn 10) J(molmiddotK) 207

The Gibbs energy of formation for CoSeO3middot2H2O and NiSeO3middot2H2O at T = 298 K 1 atm can 208

be calculated based on the determined values of of HΔ and o

f SΔ We obtain of GΔ (298 K 209

CoSeO3middot2H2O cr) = ndash9374 J(molmiddotK) of GΔ (298 K NiSeO3middot2H2O cr) = ndash9324 J(molmiddotK) 210

Selivanova et al (1964) measured the heat of reaction between Na2SeO3 solution and 211

Co(NO3)2middot6H2O(cr) and from this they calculated of HΔ (298 K CoSeO3middot2H2O cr) to be ndash112421 212

kJmol The same authors (Selivanova et al 1963) measured the heat of reaction between Na2SeO3 213

solution and Ni(NO3)2middot6H2O(cr) and obtained of HΔ (298 K NiSeO3middot2H2O am) to be -112173 214

kJmol The difference between these values and our data is about 1 It should be noted that 215

although in the case of NiSeO3middot2H2O the received value was obtained for an amorphous phase it is 216

very close to of HΔ (298 K CoSeO3middot2H2O cr) (Selivanova et al 1964) (the difference is 25 217

kJmol and the value for cobalt selenite there is less) For our data we observe the same 218

relationship as the value of of HΔ (298 K CoSeO3middot2H2O) is less by 20 kJmol than o

f HΔ (298 K 219

NiSeO3middot2H2O) We suppose that both results of Selivanova et al (1963 1964) were obtained on 220

amorphous phases 221

The relevant results of our study are listed in tables 7 8 Our value for So(298 K) is roughly 222

25 (for CoSeO3middot2H2O) and 14 (for NiSeO3middot2H2O) lower than given in Selivanova et al (1963 223

1964) Calculation of So(298 K CoSeO3middot2H2O) (Selivanova et al 1964) and So(298 K 224

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

8

NiSeO3middot2H2O) (Selivanova et al 1963) is performed by means of the of GΔ values calculated from 225

the data of Thukhlantsev and Tomashevsky (1957) on the solubility of cobalt and nickel selenites 226

The rather big difference between standard Gibbs energy and entropy of the formation of cobalt and 227

nickel selenites is caused by a two order of magnitudersquos difference between the solubility products 228

measured in Thukhlantsev and Tomashevsky (1957) viz ((16plusmn08)middot10ndash7 for CoSeO3 and 229

(1plusmn01)middot10ndash5 for NiSeO3) The solubility of the salts was studied by Thukhlantsev and Tomashevsky 230

(1957) without the identification of solid phases (by X-ray diffraction or by Schreinemakerss ldquorestrdquo 231

method) and without measurements of selenium concentration in the saturated solution Therefore 232

we think our So(298 K) values determined directly by low-temperature calorimetry should be 233

regarded as superior to those calculated from solubility data of Thukhlantsev and Tomashevsky 234

(1957) 235

Based on the results of this investigation table 9 contains smoothed Срdeg(T) values between 236

T = 0 K and T = 320 K for CoSeO3middot2H2O (cr) and NiSeO3middot2H2O(cr) Values for So and the 237

functions [Hdeg(T)-Hdeg(0)] and [Gdeg(T)-Hdeg(0)] are also included 238

Implications for Environmental Mineralogy 239

These results motivate a re-evaluation of the natural conditions under which selenites and 240

selenates replace selenides and sulfides in the oxidation zones of sulfide ore deposits or upon 241

weathering of technologic waste Special attention should be given to a substantiation of the 242

thermodynamic approach for modeling of mineral-forming processes in near-surface conditions 243

The values of ΔfGdeg for CoSeO3middot2H2O and NiSeO3middot2H2O were used to calculate the EhndashpH 244

diagrams of the CondashSendashH2O and NindashSendashH2O systems Previously these diagrams were calculated 245

by Krivovichev et al (2011) on the base of published data on solubility of CoSeO3middot2H2O and 246

NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 1957) In this study calculation and construction 247

of Eh-pH diagrams were spent by means of software Geochemistrsquos Workbench (GMB 70) The 248

calculation of the diagrams was predated by the introduction of new data for CoSeO3middot2H2O and 249

NiSeO3middot2H2O into the database and the specification of some constants The activity coefficients 250

are calculated from the DebyendashHuumlckel equation Eh-pH diagrams of NindashSendashH2O and CondashSendashH2O 251

systems have been constructed for the average contents of these elements in acidic waters of the 252

oxidation zones of sulfide deposits (Krainov et al 2004) 253

The EhndashpH diagram of the CondashSendashH2O system (Fig 5a) contains in addition to the stability 254

field of native selenium a stability field of Co3O4 which is unknown in nature and the stability 255

fields of CoSe (freboldite) and cobaltomenite formed in the neutral environment while Eh is not too 256

high The EhndashpH diagrams of the NindashSendashH2O system (Fig 5b) contains the stability fields of 257

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

9

native selenium NiSe2 (penroseite) and Ni3Se4 (wilkmanite) and a wide field of NiO (bunsenite) 258

and a field of ahlfeldite 259

So the behavior of selenium the nearest geochemical counterpart of sulfur in the surface 260

environment can be quantitatively explained by variations of the redox potential and the acidityndash261

basicity of the mineral-forming medium Precisely these parameters determine the migration ability 262

of selenium compounds and its precipitation in the form of various solid phases 263

264

Acknowledgments 265

This work was supported by Saint-Petersburg State University grants (338682011 and 266

338832012) and DFG research foundation DE 41240-1 267

268

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

10

References 269

Charykova MV Krivovichev VG and Depmeier W (2010) Thermodynamics of arsenates 270

selenites and sulfates in the oxidation zone of sulfide ores II Systems M1 M2 SО4 ndash H2O 271

(M1 M2 = Fe2+ Fe3+ Cu2+ Zn2+ Pb2+ Ni2+ Co2+ H+) at 25degC Geology of Ore Deposits 52 272

759ndash770 273

Dachs E and Geiger CA (2006) Heat capacities and vibrational entropies of mixing of pyrope-274

grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions A low temperature calorimetric 275

and thermodynamic investigation American Mineralogist 91 894ndash906 276

Gatta GD Richardson MJ Sarge SM and Stoslashlen S (2006) Standards Calibration and 277

Guidelines in MicroCalorimetry Pure and Applied Chemistry 78 1455ndash1476 278

Krainov SR Ryzhenko BN and Shvets VM (2004) Geokhimiya podzemnykh vod 279

Teoreticheskie prikladnye i ekologicheskie aspekty (Geochemistry of Subsurface Water 280

Theoretical Applied and Environmental Aspects) Moscow Nauka (In Russian) 281

Krivovichev VG Charykova MV Yakovenko OS Depmeier W (2011) Thermodynamics of 282

Arsenates Selenites and Sulfates in the Oxidation Zone of Sulfide Ores IV Eh-pH diagrams 283

of the Me-Se-H2O systems (Me = Co Ni Fe Cu Zn Pb) at 25degC Geology of Ore Deposits 284

53(7) 514ndash527 285

Lelet MI Sharkov VV Nurgaliev IF and Suleymanov YeV (2011) A new hardware 286

solution in reaction calorimetry Vestnik of Nizhny Novgorod State University 3(1) 97-101 287

Olin A Nolang B Osadchii EG Ohman L-O and Rosen E (2005) Chemical 288

thermodynamics of Selenium Amsterdam Elsevier 851 p 289

Seby F Potin-Gautier M and Giffaut E (2001) A critical review of thermodynamic data for 290

selenium species at 25 degC Chemical Geology 171 173-194 291

Selivanova NM Leschinskaya ZL Maier AI Muzalev EYu (1964) Thermodynamic 292

properties of cobalt selenite CoSeO3middot2H2O Izvestia Vuzov Khimia i khimicheskaya 293

tekhnologia 7 209-216 (In Russian) 294

Selivanova NM Leshchinskaya ZL Maier AI Strelrsquotsov IS Muzalev EY (1963) 295

Thermodynamic properties of nickel selenite dehydrate Russian Journal of Physical 296

Chemistry 37 837-839 297

Suleimanov EV Golubev AV Alekseev EV Geiger CA Depmeier W and Krivovichev 298

VG (2010) A calorimetric and thermodynamic investigation of uranyl molybdate UO2MoO4 299

Journal of Chemical Thermodynamics 42 873ndash878 300

Thukhlantsev VG and Tomashevsky GP (1957) The solubility of the selenites of certain metals 301

Journal of the Analytical Chemistry of the USSR 12 303-309 302

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

11

Treatise on Geochemistry Vol 9 Environmental geochemistry Ed B S Lonar (2004) 303

Amsterdam Elsevier Pergamon 304

Varushchenko RM Druzhinina AI and Sorkin EL (1997) Low-temperature heat capacity of 305

1-bromoperfluorooctane The Journal of Chemical Thermodynamics 29 623ndash637 306

Vlaev LT Genieva SD and Gospodinov GG (2005) Study of the crystallization fields of 307

cobalt(II) selenites in the system CoSeO3ndashSeO2ndashH2O Thermal Analysis and Calorimetry 81 308

469-475 309

Vlaev LT Genieva SD and Georgieva VG (2006) Study of the crystallization fields of 310

nickel(II) selenites in the system NiSeO3ndashSeO2ndashH2O Journal of Thermal Analysis and 311

Calorimetry 86 449-456 312

Wagman DD Evans WH Parker VB Schumm RH Halow I Bailey SM Churney KL 313

and Nuttall RL (1982) The NBS tables of chemical thermodynamic properties Selected 314

values for inorganic and C1 and C2 organic substances in (SI) units Journal of Physical and 315

Chemical Reference Data 11 Supplement 2 1-392 316

Wildner M (1990) Crystal structure refinements of synthetic cobaltomenite (CoSeO3middot2H2O) and 317

ahlfeldite (NiSeO3middot2H2O) Neues Jahrb Mineral Monatsh 353ndash362 318

319

320

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

12

TABLE 1 Cell parameters of CoSeO3middot2H2O and NiSeO3middot2H2O 321 Compound CoSeO3middot2H2O NiSeO3middot2H2O

Space group P21n P21n

а Aring 6496 (1) 65322 6494(6) 6441 (2) 63782 6442(9)

b Aring 8809 (2) 88251 8810(6) 8746 (2) 87734 8751(2)

c Aring 7619 (2) 76455 7614(4) 7522 (3) 75467 7521(0)

β 0 9887 (1) 80478 98872(4) 9900 (2) 81451 99008(1)

V Aring3 43074 43467 430493 41854 41761 418828

Wildner 1990 Vlaev et al

2005

This work Wildner 1990 Vlaev et

al 2006

This work

Formula units per

cell

4 4

322

323

324

TABLE 2 Infrared absorption spectra of NiSeO32H2O and NiSeO3H2O 325 CoSeO3middot2H2O NiSeO3middot2H2O Band assignment

This work Vlaev et al 2005 This work Vlaev et al 2006 492 492 501 500 δ(SeO3)2- 577 576 578 579 νCondashO (νNindashO) 697 700 703 700 νas(SeO3)2- 792 790 799 800 νs(SeO3)2- 813 815 842 841 νs(SeO3)2- 924 ρH2O 1507 1500 1527 1516 δ(OH)(H2O) 1613 1613 1624 1628 δ(OH)(H2O) 2938 2942 2916 2916 ν(OH)(H2O) 3130 3129 3118 3126 ν(OH)(H2O) 3220 3224 3197 3200 ν(OH)(H2O) 3429 3430 3452 3452 ν(OH)(H2O)

326

327

328

TABLE 3 Standard enthalpy of reactions (2) ndash (6) used for the calculation of 329 o

f HΔ (298 K CoSeO3middot2H2O cr) and of HΔ (298 K NiSeO3middot2H2O cr) 330

Reaction (AII - Co2+ Ni2+) ΔrHdeg(298) (kJmol)

AII - Co2+ AII - Ni2+

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

13

1 Na2SeO3(cr) + (H2SO4 solution) rarr (solution А1)

-4042 -4136 -3992 -4007 -4017 -3997 -4046 -4177 -4097

Mean -406 plusmn 05

2 AIISO4middot7H2O(cr) + (solution А1) rarr (solution А2)

3600 3675 3614 3572 3462 3556

3458 3440 3406 3494 3486

Mean 358 plusmn 07 Mean 3457 plusmn 044 3 5H2O + (H2SO4 solution) rarr (solution В1) Mean 0

4 Na2SO4(cr) + (solution В1) rarr (solution В2)

2176 2044 2042 2123 2172 2147

Mean 212 plusmn 06

5 AIISeO3middot2H2O(cr) + (solution В2) rarr (solution В3)

-1284 -1295 -1332 -1290 -1293 -1265 -1254 -1317 -1307 -1393 -1269 -1289

-1309 -1243 -1234 -1286 -1265

Mean -130 plusmn 02 Mean -1267 plusmn 038 331 332

333 334 335 336 337

TABLE 4 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for CoSeO3middot2H2O (cr 338

М=221922gmol) 339

Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Series 1 185 2858 568 3494 1054 8001 1968 1347

81 1134 188 2943 578 3595 1074 8162 1989 1358

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

14

83 1132 190 305 587 3689 1094 8320 2015 1369 84 1134 193 314 596 3789 1114 8465 2045 1380 86 1138 196 324 606 3892 1134 8609 2076 1393 87 1160 199 337 605 3872 1154 8756 2106 1407 88 1174 205 358 614 3969 1174 8898 2137 1422 90 1178 213 393 628 4113 1194 9048 2167 1435 91 1192 222 430 633 4164 1214 9180 2198 1448 93 1200 231 469 640 4234 1234 9327 2228 1461 94 1218 239 507 647 4310 1254 9462 2259 1477 95 1229 242 530 652 4356 1274 9601 2289 1490 97 1243 251 577 667 4506 1295 9724 2320 1501 98 1257 260 628 679 4628 1315 9852 2350 1515 100 1278 269 681 687 4711 1335 9979 2381 1516 102 1300 278 738 699 4824 1356 1013 2411 1537 104 1315 287 799 707 4900 1376 1025 2441 1554 107 1347 296 862 716 4988 1396 1038 2472 1567 110 1375 305 929 726 5084 1416 1050 2502 1584 112 1409 315 998 737 5184 1437 1063 2532 1590 115 1445 324 1071 745 5261 1457 1075 2563 1601 118 1476 333 1146 755 5351 1477 1088 2593 1614 120 1517 343 1225 769 5482 1498 1099 2623 1627 123 1558 353 1308 775 5533 1518 1110 2653 1640 126 1595 362 1391 783 5609 1539 1124 2683 1650 128 1621 372 1471 794 5703 1559 1136 2713 1661 131 1660 385 1604 804 5795 1579 1147 2743 1672 134 1702 394 1699 814 5943 1600 1158 2772 1684 137 1748 404 1782 825 6077 1620 1170 2802 1695 139 1791 414 1886 834 6176 1641 1181 2832 1705 142 1832 424 1982 848 6305 1661 1191 2862 1716 145 1886 434 2066 863 6428 1682 1206 2891 1727 148 1936 443 2174 878 6557 1702 1214 2921 1736 151 1988 453 2267 893 6700 1723 1225 2950 1748 153 2049 463 2364 908 6817 1743 1236 2979 1764 156 2107 473 2470 923 6938 1764 1247 3013 1779 159 2168 482 2585 938 7055 1784 1257 3052 1787 162 2242 492 2687 953 7178 1805 1267 3091 1799 165 2314 502 2788 1825 1279 3130 1811 167 2381 511 2886 Series 2 1846 1290 3168 1824 170 2444 521 2985 967 7310 1866 1299 3206 1836 173 2523 531 3089 982 7425 1887 1309 3244 1849 176 2599 540 3191 997 7529 1907 1318 3282 1861 179 2687 550 3293 1014 7713 1928 1329 182 2788 559 3394 1034 7863 1948 1341

340 341

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

15

342 343

TABLE 5 Raw low-temperature heat capacity Срdeg (J(molmiddotK)) data for NiSeO3middot2H2O (cr 344 М=22168 gmol) 345

346 Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg Т (K) Срdeg

Series 1 195 3770 566 31227 930 63731 2018 133012 92 0728 198 3880 576 32084 950 65563 2059 135072 95 0872 201 4021 586 33056 969 67540 2100 137109 98 0883 207 4342 597 35035 989 69610 2140 139153 100 1005 216 4670 607 35968 1009 70902 2182 141444 103 0950 224 5081 617 36815 1034 72060 2223 143041 106 1093 246 6245 628 36784 1093 76141 2263 144941 109 1069 259 6865 638 38288 1123 78299 2304 146871 112 1110 267 7214 648 39000 1157 80558 2345 148806 114 1175 276 7459 659 40124 1191 82838 2386 150591 117 1331 287 8159 669 40641 1221 85052 2426 152460 120 1334 301 8810 679 42266 1251 87123 2467 154283 123 1403 312 9406 690 42878 1281 89179 2508 155950 126 1447 322 9691 701 44024 1312 91200 2549 157793 128 1433 331 10786 716 45406 1342 93261 2589 159207 131 1620 341 11686 736 47343 1372 95225 2630 161071 137 1819 351 12265 757 48559 1402 97193 2670 162737 140 1852 361 13039 777 50451 1433 99105 2711 164221 143 1936 371 13581 786 51636 1463 101115 2751 165926 146 2003 380 13972 1494 103047 2792 167483 148 2137 390 14803 Series 2 1524 104810 2832 169542 151 2392 400 15896 669 40641 1555 106676 2873 170628 154 2298 410 17244 679 42266 1585 108581 2913 171893 157 2494 420 18190 690 42878 1616 110449 2953 173414 160 2479 430 19271 701 44024 1646 112337 2993 174750 163 2536 440 19740 716 45406 1677 114064 3039 177278 166 2686 450 19994 736 47343 1708 115879 3092 178302 169 2791 460 20868 757 48559 1738 117561 3145 179787 172 2892 470 22517 777 50451 1769 119299 3197 181712 175 2993 481 23229 786 51636 1799 120968 3248 183555 178 3011 491 24145 809 53749 1830 122645 3299 185638 180 3097 501 24898 830 55407 1860 124317 3350 187732 183 3315 523 27270 850 57030 1891 125994 3400 189609 186 3334 535 28300 870 58626 1922 127689 189 3541 546 29307 890 60315 1952 129309 192 3594 556 30403 910 61972 1983 130914

347

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

16

348

TABLE 6 Best-fit coefficients for use in the Срdeg polynomial in eq (10) for three temperature 349 intervals 350

351 352 353

TABLE 7 Comparison of thermodynamic functions for CoSeO3middot2H2O (cr) 354

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1766 plusmn 10 1832 plusmn 10 -11353 plusmn 23 -9374 plusmn 25

NM Selivanova et

al (1964) - 2286 (cr) -112421 (cr) -9406(cr)

355 calculated using the data on solubility of CoSeO3middot2H2O (Thukhlantsev and Tomashevsky 356

1957) 357

358

359

TABLE 8 Comparison of thermodynamic functions for NiSeO3middot2H2O (cr) 360

Reference Срdeg(29815 K)

(J(molmiddotK))

Sdeg(29815 K)

(J(molmiddotK))

ΔfHdeg(298 K)

(kJmol)

ΔfGdeg(29815 K)

(kJmol)

This work 1743 plusmn 10 1729 plusmn 10 -11333 plusmn 22 -9324 plusmn 25

NM Selivanova et

al (1963) - 1968 (am) -112173 (am) -9280(cr)

361 calculated using the data on solubility of NiSeO3middot2H2O (Thukhlantsev and Tomashevsky 362

1957) 363

T (K) k0 k1 k2 k3 k4 k5 k6

AII - Co2+

81-15 -795514 215203 -978616 194228 355448 -11359 0159242

15-47 367663 -940978 20223 -129514 -810942 0138739 -0000847

47-328 4427 -7431middot106 441169 -356184 -066795 0002145 -2137middot10-6

AII - Ni2+

92-16 0101264 - - - -004141 -748middot10-4 00004854

16-50 505953 343758 -447731 46812 -70692 017244 -0001236

50-340 -292949 12469middot107 -534922 244599 190914 -000352 2833middot10-6

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

17

364 365 366 367 368 369

TABLE 9 Smoothed values for the thermodynamic functions of AIISeO3middot2H2O (AII ndash Co2+ Ni2+) 370

Т Срdeg Hdeg(T)-Hdeg(0) Sdeg(T) -[Gdeg(T)-Hdeg(0)] AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+ AII - Co2+ AII - Ni2+

[0] [0] [0] [0] [0] [0] [0] [0] [0] 20 3409 3982 002919 002052 2491 1328 002064 000604440 1744 159 02174 02051 8463 7275 01211 00859 60 3821 3539 07716 07082 1941 1722 03931 03252 80 5752 5304 1736 158 3315 2963 09159 07904 100 7557 7041 3081 2807 4809 4325 1727 1518 120 9089 835 4752 434 6327 5719 2841 2522 140 104 9707 6703 6148 7829 711 4257 3805 160 1158 1095 8904 8215 9296 8488 597 5365 180 1265 121 1133 1052 1072 9845 7973 7199 200 1364 1319 1396 1305 1211 1118 1026 9302 220 1448 1422 1677 1579 1345 1248 1281 1167 240 1528 1512 1975 1873 1474 1376 1563 1429 260 1617 1597 2291 2184 1601 150 1871 1717

27315 1668 1651 2507 2398 1682 1581 2087 192 280 1695 1679 2622 2512 1723 1622 2203 2029

29815 1766 1743 2935 2823 1832 1729 2526 2333 300 1774 1751 2968 2855 1843 174 256 2365 320 1834 1818 3329 3212 1959 1855 294 2725

Т (K) Срdeg (J(molmiddotK)) Hdeg(T)-Hdeg(0) (kJmol) 371 Sdeg(T) (J(molmiddotK)) -[Gdeg(T)-Hdeg(0)] (kJmol) 372

373

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

18

Figure Captions 374 375

376 377

Figure 1 Deviations of experimental Срdeg on benzoic acid from (Gatta et al 2006) 378 379 380 381

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

19

382 FIGURE 2 X-ray powder diffraction diagram of CoSeO3middot2H2O and NiSeO3middot2H2O (curve lines are 383

experimental results black vertical lines are PDF-2 entries 01-080-1391 (for cobaltomenite) and 9-384

009-364 (for ahfeldite)) 385

386 387 388 389 390

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

20

391 392 FIGURE 3 Plot of our experimental low-temperature Cpdeg results for against temperature between T 393 = (8 and 328) K for CoSeO3middot2H2O and T = (10 and 340) K for NiSeO3middot2H2O Data for 394 CoSeO3middot2H2O are shown as rings and those for NiSeO3middot2H2O as solid triangles 395 396

397

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

21

398 399

FIGURE 4 Plot of heat capacity against temperature to illustrate the deviation of the experimental 400 low-temperature Cpdeg values from the polynomial fit (Eq (10) and (table 6) Data for CoSeO3middot2H2O 401 are shown as rings and those for NiSeO3middot2H2O as solid triangles 402 403

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409

22

404

405

CoSe+Se0

CoSeO32H2O

Cobaltomenite

Co2+

Eh B

0

05

10

-05

Co3O4

CoSeFreboldite

60 121082 4 14pHa

HCoO2

Se0

Selenium

NiSe2 + Se0

NiSeO32H2O

Ahlfeldite

Ni2+

Eh B

0

05

10

-05

NiOBunsenite

Se0

60 121082 4 14pH

NiSe2Penroseite

NiNi2Se4Wilkmanite

NiSeO32H2O+Se0

b 406

407 FIGURE 5 EhndashpH diagrams of the CondashSendashH2O (a) and NindashSendashH2O (b) systems at 25degC The activities of the components (a) aΣSe = 10ndash3 aΣCo = 10ndash2 408

and (b) aΣSe = 10ndash3 aΣNi = 10ndash2 409