Vol. SSVII . , Kn Z.1 WATTS & TEMPANY-THE POLARIMETRIC .DETERMINATION OF SUCROSE. 53

C.O.

10 20 40

10 40 40

-

-

London Swtion. dIecting held at Btrrlington Houae otb Monday, Dee. Znd,

1007.

a\’. --0,..9 -1.0

3.7

-2.3 14 0.4 7.6

7. a

BfR. R. J. FRISIVELL I S THE CHAIR. -- THE POLAHIMETRIC DETERIIINATION OF

SUCROSE. THE EFFBWJ! OF CLARIFICATION WITH BASIC

LEAD ACETATE OX THE OPTICAT, ACTIVITY AND COPPER RXDUCIKG PO\V’EB OF SUGAR SOLUTIONS. 11Y FRANCIS WATTS, C.N.G., D.SC., F.I.C., ASD

11. A. TEXI’ANY, BAG., F.I.C.

At the prcticnt tine no inore vexed question exists in thc province of n plicd cheniistr devoted to the npgnr industry tlinii t t n t regnrding t i e vnlidity of thc siniplc direct polnriiuctric rcnding of n ntnndnrd solution of a comniercinl HU rar w a iiiensiirc of the actual niiioiint of sucrose contninch in it. It lins h e n urgcd, nnd justly,

that under certain conditions 8uch a determinntion is likely to Lo very cornidcrab1 wide of the truth, gct nt the mine time the hold whici the method tins obtained owr the sugnr industry of thc western hemisphere, combined with its utility nnd simplicity in prncticc render it oxtrcmcly iinlikely that i t cnn over become crndicntcd in fnvour of niore nccurntc but nt the sniiio time inorc lnborioils nnnlyticnl proccsscs. On this ncoount i t boconica n rnnttcr of prime ncccssity that the condition9 under which the deterniinntion is cnrricd out shall IJC (10 nccrirato 08 possible, nnd that stnndnrd iiicthodn of yerfornh thc test shell univcrsnlly prevnil ti0 that nu two rrnn$stu situntcd in nny pnrts of the world, slid bc nblc, worliin uiidcr them conditions, to obtain identical rcsiilts wficn working on iclenticnl tiniuples.

The nttention of siignr chemists is now being Inrgely dircctod townrds tho securing of nuch uniformity, nnd the work horc to bc rccordcd is u. continuation of cfforh by ournclves in this direction. In previous coinniunicntions suggestions linvc ~ICCII put forwnrcl Iiy us for the iiuificntion of methods of performing this determination. Thew hnvc nplxnrcd in tho West Tndinn Uullotin ns follows :--VoI. VI, pp. 32-60,

two of ttic!m Iiavo ixcn rcprduccd in tiic iitcrnntionnl sugar ,Journal :-Vol. VII, pp. 391-398, nnd VoI. VII, yp. 440- 454, nnd nbtracb heve appcnrcd in this Journal. 1905, 817; 1900, 957, nnd 1DO8,. 31.

Tlic results orrivod a t in thcso pnpcm may tx briefly r;uinniariscd tlius :-

1. Rim in tuiiqmaturo occasions n lowering of tlic specifio rotation of suerose which, with the norinnl wight for tho Ventzkc scnlc, uniounta to 0*000148.t.N, whcro t is the difference betwccn the tcmporaturo of oborvntion nnd thnt a t which the polnrimnctcr wns stnndnrdizcd iind N the Ventzkc wcnlo rending. If this in cotnbincd witti the ofTcct of tcmpcrnturc on the qunrtz wedge, Jobin’s forrnllln, nnd on the po1nriuater tulw it becomes O.Wd1.t.N.

2. Clarification of coinmercinl H U ~ U solutions with solutions of hnxic Iced ncetato is roduotivn of crror owing to tlio voiunie occirpictl by t i e prcci jitnto. 3. ‘Phe crror uiny be avoidcd by the URC 01 nnhydrous

bnsic lend ncetnta as n clnrifying agent, na propwed by

4. In tho inctbd of Clcrgct as adopted to tropical conditiona wu ndvocnted the use of sntallcr ooncentrntiona of iwid thnn thorn iiscd by Clerget and Herzfcld, wliemby tho fesr of revomion during licnting in obviated.

Our recommendations coilsequent on tlrcse rcsultn were-

1. Use a noi4ht of 20 grin% of tlio noniplo of sugnr uiider oxaminstion, tlirsolve in clintillcd wutcr uncl iirrke i i p to LOO trim am

that thiq Iilethod i H h b l C to HeriOUH HOUrCCS O f CrTOr,

Vol. VlI, pp. 132-1‘10, Vol. VIII, p . 111-110;

Jrorne.

2. Clarify by moans of anhydrous h i e lead acetate, rvoidi excess.

3. Pyarhe at the temperature a t which the solution s repred and correct for t e m y t u r o by the formiilia, oo~rmntion-0.003ItN, whew is tho Ventzko scnio .ending and t is tho difference between the temperature ,f observation nnd that a t which the instrument was jtandardised.

4. In the Clerget process, use 3 0.0. of hydrochloric icid to 100 O.C. of normal sugnr solution; invcrt by heating for 16 minubs a t 08’ C.. nnd in tro icnl Forking polnriso nt air tompcrnture, 30’ C. being t fc standnrd ; the formula for that tcmpcrnturc is ’ , t h i n g

tho difference between the tempernture of ohcrvation nnd 30OC.

Tlic results nrrived n t by Horne nnd ou~clves in favour of tho UHC of nnhgdroua basic lcnd ncetate hnve given rbo to D certain nmount of criticism. Proininent among lhese critics hnve been H. and 1, Pellet, who hnvc innin- tnincd thnt thc dry defecation method, ns npplicd to wgnr solutions, is erroneous, by reaqon of tho fact that in tlie cnse of su nr solutions clnrificd by nieana of D. solution of basic Lad ncetate the prccipitnto nborhd sufficient sugar froin tho solution to ncutrnlise tlio con- ccntrnting cfTect occasioned by ita presencc, nnd tlint in consequence tho polorisat ions of solutiona clnrilied bv the dry defecntion method nro linblo to bo too low I& reason of thc sugnr absorbed from tlie solution bg tho preci itatc. These criticisms hnve k c n met by Horne, w\o in a paper rcccntlv published in the Journal of the American Cheniicnf Society and repro. ducod in tlic Intcrnationnl Sugar Journnl (IX, 2?7-233), showed thnt thc lend prccipitnte, instcad of nbsorbing fiugnr, took up a sninll niuount of wnter, which, howcvcr, wns so small ns not to nffect nintcrinlly tho validity of the dctcrniinntion.

A nrt from these special considcrntions, the process of Zfccnting sugnr solutions by nicnns of bnsic tend nectato is, n t the prcscnt time. considered to ~JOSSCSH fiindaiiicntnl innccurncics by rcnson of the interaction of the lcnd snit with tlic vnrious orgnnic impuritics cou- tnincd in conimcrcinl sugnrs. juices nnd liquors. Chief ninon6 thcfie disturbing minor renctionv is the intcr- nction of the lead salt witli nny iiivcrt sugnr contnincd in the HU mr solution, diich, it is held, is liable to occasion serious hernngcnicnt of tlic dctcrniinntion by rewon of the formation of lend lcvulosnto from which Iiintcriiil ultcrntion of the rotntion is linble to renult.

The influcncc of lend snlts on the qwciflc rotation of invert sugnr wns firnt pointed out liy C. H. Gill in 1871 (J. Chein. Soc., 24 (1871) 91). His r c d b were rcisntcd by Bittmann in 1880 (Zcit8. fiir Riihnruckor-Ind., 1880, R76). The followin5 table of Bittiiinnn’s results is taken f r y i Lnndolt’s Opticnl Hobtioil of Orgnnio Substances, 1902 (Americnn edition), p. 591%

1zs.osr 1. 2

l)nsIn lend

solution. I I I

0.e. 60 60 60 60 10 10 10

G

0.0. Go 40 90 10

1 40 :10

6 c

Gill’s original results wcrc not nccessible to us, and the rcRiilttl of Bittinem dcul with the cffoct of qunntitics of basic lcnd ncetata niuch lnrgcr thnn the CXCCHRCR likely to tm nict with in uotual nnnlyticnl prnctico.

A t tho present tinie ideas on tho subjeot appear to IJO of tlie vaguest description ; by soiiie it is klieved that the effeot of bmio load ncctate on lovuiofic is to prceipi. tste a n insoluble ooinpouiid, l i d it lrw h e n suggested that tho ?won for tho usortion thnt the mducing sugars in cane juice ure optically inaetivo is, tlint in cane juicw

64 WATTS & TEMPANYTHE POLABIMETRIC DETERMINATION OF SUCROSE. [Jan. 31, 1908.

clarilied with baeio lead acetate, tho optically active excess of lewlosc is rendered inactive by recipibtion 0 load lcvulosnto (H. Pellct, Int. Sugar J., &I, p. 468).

On this nccount it appeared to us thnt i t niight bo profitable if n eriticnl investigntion werc mndc of the notion of lend snlts (nnd especially of smnll quantities thereof) on the various constituents of rnw canc sugnm nnd canc juices with tho idea thnt tho total effect of lcad on sugar solutions might best be gnuged by n study of it8 influcncc on thc vnrious individual components. I n undertaking this work thc starting:$oint was tho nction of bnsic lcnd ncetnte on pure qolutiom of invcrt sugnr.

Ezpe r imental.

A solution of invcrt sugnr \vas prepnrcd by inverting nn npproximntely 20 p r cent. solution of pun, cnne sugnr with oxnlic ncid at 70" C., tho end of thc renction hcing nsecrtnincd by menn.. of tho polnriacopo. Tho oxnlic ncid w+as neutrnlised by barium hydroxide, the point of neutrnlity being nsccrtnined by menns of phenolphthalein, tho prccipitnted barium oxnlnte was filtered off.

"he basic lend acetate solution employed wns prepnred nccording to tho dircctions in Allen's Commeroinl Orgnnic Analysis, Vol. I, p. 251, 1808 edition, nnd had a sp. gr. of 1-24? a t 29'/26*7o C., nnd a solid conknt of npproxi- mntcly 32 r cent. b wight.

Excens orbasic lendrncotato solution w n ~ nddcd to n meurured qunntity of tho invert solution nnd tho mixturc was loft for revcrnl dnys; at the end of that time no traco of prccipitation had occurred, thus effectively negativing the nuggestion thnn nn insolublo lead lovulosntc is formed by the notion of bnsic lead ncetato on invcrt su nr solutionn.

f n studying the effect on thc optical nctivity, 26 C.C. of the invert sugnr solution were in ench case mcnsured out, by menns of n double-innrkcd 26 C.C. stnndnrdised pipctte. into a 50 C.O. stnndnrdised llask, nnd the required amount of lead solution nddcd from n burcttc ; the Rolution WBH nindc up to Fio C.C. n t W C. and polnrincd in n 200 m m jnckckd polnrinickr tube, round which n strenni of water nt 30° C. was kept flowing during the coumo of taking the obsorvntions.

The results obtnined were as follows (in nll cases tho figures given for tho polarisntion,nre tho mcnns of n numbcr of rendinge) :-

so. of I Lead acetoto I ridded*

I C.C.

experiment.

4.0 5.0

10.0 I 16.0

Polnrlsntlon of solutlou.

'U. -10.40 -10.34 -10.16 - 9.55 - SO5 - 8.25 - 7.08 - 4.71 - 1.59

Tho nEect of tho lend snlt on the opticnl nctivity ~II shown in n lnnrkcd degrec. It has becn stnkd thnt this cffcct cnn hc neutrnlised by tho nddition of ncctic acid to the solution whcrcby thc compound of basic load ncetnte with Icvulwc is destroyed and the origiunl rotation of the solution is restored. G. F. Spencer ha? on thin nccount proposcd tho nddition of a smell nniount of acetic acid to sugar solutions and juices clarified in this manner as n menm of climinntin this error.* To investigeto this point, 60 C.C. of tho solution from cxpri- ment No. 6 nbove wow tnken. to i t W'BB added 1 c.0. of glncinl noetio acid, the inixturo mndc up to 56 C.C. at 30° C., nnd, rend nt thnt tempernturn in n 220 nim. jwkoted polnrimctcr tubo, gnvc n polnrisntion of -10.41. !I'his shows that tho nddition of ncctic ncid had over- conic the cffect of tho lend snlt. In ordcr to ascertnin tilo minimum amount of ncotio acid rcquhd to effcct

Handbook for Suger Hinufrcturerr (l8@3), p. 38.

the decomposition of nn amount of lend levulosnte similnr to thc above, n solution was repnred bv taking 100 C.C. of invert sugnr solution ngding to it approximately 20 C.C. of basic lend ncctatc and mnking up to 200 C.C. lit 30' C. To cqunl portions of 50 ex . ench of this solution, increasingly largo nniounta of ncctic noid w r o ndded until tho original opticity of the solution \vm rcstorcd. the solutions being mndc np to 65 C.C. nt 30°C. and polnrised in n 220 mm. tube. A control solution wns prepnred by makin up 26 C.C. of the invcrt sugnr solution to cio C.C. n t 300 8. without nddition, nnd polnrisin jn n 200 mm. t u b . AII polnrisntions wcrc performei ui tubes jncketed with wntcr nt 30" C. The results obtnined 1vcw as follows :-

Polnrisatlon of solution. I Acetic acid

added. I No. Of cxperlrnent.

I* 2 3 4 5

C.C. - - 0.2 0.3 0.4

'V. -10.44 - 7.82 - 8.90 -10.25 --10*46

I - . . . - . . - . Coutrol: no lend.

Theso results show thnt 0.4 O.C. of glacis1 acetic is sufficient to ncutralisc tho effect of 5 C.C. of basic lend acetate solution.

Assuming thnt thc formula of basic lead ncctnte is Pb(C2H30z)zPb0 nnd tho content of the dry snlt in the solution to hc 32 pcr cent., 6 C.C. of this solution would contain 0.81 grni. of lend oxidc and to neutrnlisc this would require 0.44 grnis. of ncctic ncid equivnlcnt to 0.42 C.C. nt 3OoC., the nrnount nctunlly found being 0.4 C.C. Hcncc it appnm thnt the nffcct of tho lend anlt is Riniply duo to direct conibinrition of the basic portion of tho lend snlt to form n levulosnte, or lcvulosntcs. Thin conclusion wns confirmed bv prcpnring n solution of invcrt sitgnr nnd polnrising it .in n 200 nim. tubo ; 50 C.C. of this solution wcrc then tnken, mndc u p to G6 C.C. with a solution of neutrd lend acetate (sp. 1.186, npproximntely 26 per cent. strength), nnd poErised in n 220 nim. tube ; tho polorinntion without lend ncctnte as -11.3' V., whibt with lend ncctato it wa. -11.30 V.

In thc above rcsults tho most striking fenturo is the oxcccdingly smnll effect which tho initinl smnller nmounts of lend acetate linvc on tho optical nctivity of tho solution. Thus, 0.5 and 1.0 C.C. of lcnd in 50 C.C. of solution only nffcct the rotntion by O*Oo" V. nnd 0*36 V. rcspcetivcly, nnd it must be rcinembered thnt these nmoiintv would cormpond to excesties of 1 nnd 2 C.C. respectivoly on 100 c.c., oxcessea which nro much lnrgor thnn should occur in practice. Why tho effoct is so small is not nt first clonr, but tho fnct thnt it is so omphaeises tho necessity of nvoiding largo cxccsscs of lend nectnto in prnoticc. The results nppnr to indicate, thcrcfore, thnt whcn oxccss of lend is avoided, tho crror due to the influence of 1ead.ncctate on invert sugar is practically ne ligible in tho caso of thc ordinary run of normal sugnr sofutions nnd juicee which contain from 0.3 to 3.0 per cent. of rcducing sugnr.

In carcful working it is only in tho case of low grndc products, such ns second molnsses, o h . which niny contain from 20-30 1"' cent. of rcducing sugnr, that serious errors nrc like y to nrisc from the presencc of cxccsscs of lend ncctntc, sinco, with substances of this descri tion, ibis generally nccessnry to cmp!oy n con- sidernglc cxcess of basic lend ncctato to cffcct sotisfactory clnrificntion. In vicw of tho nbovc conolusions it becomes neceasnr

to nacortnin how far t h y hold good in prncticc. \ id thin object nn endcnvour wns mndc to reconstruct a solution which should npproxiniato in composition to tho nverngc run of cnno juices nnd sugnr solutions ordinnrily mot with, and to study tho cffcct of lend clnrilicntion thoreon.

A quantity of lend precipitate from tho dcfocntion of cane juices during tho preceding crop wna collected. The prnotico WM to ecrape tho precipitstee into 8 luge

beaker filled with water; this was allowed to stand, nnd tho accumulating lcnd conipound wnshcd daily by dccnntation. When a sufficient unntity hnd nccumu- lntcd i t was filtered off through fi?tcr pnpr, nnd washed with distilcd water til1,frco from sugar ns judged by thc a-naphthol reaction. l'he lcnd compound was then susfondcd in wntcr and decomposed with sulphuretted hy ro en in the ninnncr described by tho 3fesers. Pcllct nnd I&. D. Homo (Int. Sugnr J.. 1905, SSD), nnd the resulting solution of orgnnic matter was subsequently conccntrnted to a relatively smnll bulk on the water bnth. This solution of orgnnic non-sugnr wns of n clcnr, deep brown colour, nnd icldcd n dcnvc precipitate on trent- mcnt with basic lcn8ncctatc. About 15 C.C. were diluted to 100 c.c., nnd the diluted solution, which wns clcnr nnd bright, wns examined in the polnrimeter nnd found to possess no opticnl rotation. With the nid of this solution, the effcct of thc lcnd iised in clnrificntion of solutions corresponding to thc avcrago run of raw cnnc augnra nnd cnnc juices wrm invcstigntcd. The procedure wns ns followss-4 solution of pure cnnc sugnr wns propnrcd of npprosinintely 40 per ccnt. strcn t h ; two cqunl portiolul of c.c. encli wcre mcnsurcJ out by mcnns of n stnndard doublc mnrkcd pipcttc into two nccurntcly stnndnrdised 100 C.C. flnsks, nnd to cnch of theso was nddcd 4 C.C. of the invcrt sugnr rolution already mentioned. To one of these a nicnsurcd unntitg of thc nbovc solution of orgnnic ninttcr wns ngdcd, to tho other no such addition wns mndc. Both these solutiom wero thoroughly mixed nnd nindc up to 100 C.C. at 3W C. By this nieans t w o solutions wcrc obtnincd, npproxirnnting in sucrose nnd reducing sugnr contents to tlic nvcrngc run of cnnc juices nnd norninl siignr solutions obtnincd in thc hcwnrd IslandR ; furthcrniorc, tlic solution to which non-sugar had been nddcd niny be snfely said to hnvo represented, with sonic nppronch to

solution to which non-fiugnr hnd been nddc~~$i%rrificd by nienns of dry hnvic lend ncctntc, prc nred nccording to Homo's dircctions. core bcing tnfccn to cusi1rc that tlic nrnount used ivati siniilnr to thnt ordinnrily cniploycd in nctunl prncticc by ~IH. Tho prccipitntetl solution wm filtered, with duo I)rccnutionq to prcvcnt loss by evaporation during filtration. \Vc were thus in possession of two ~olutions, encli containing tlic cnnic amounts of sucrose nnd invert sugar, but from onc of which orgnnic non-sugnr of tlic t y p normnlly occurring in cane juices hnd been ~~rccipitated by bnsic lend ncctnte ; if, now, tlic optical activity ia influenced either by tlic exccss of lcnd or bv tlic nct of prccipitntion, tlieuo two solutionv s~ iou~d ditjcr in optical activity. ~ I i c s c c s p r i . mcnts wcro rorwnted on thrcc severnl occnsions. using

exactitude, cnnc juices occurring in nctunl . Tho

freshly prcpnicd sucroyo solutions. TIIC resulting polnrirnctric rcndin s arc detailed in cnch case.*

I n ~ x p r i i i i c n b hos. 1 nnd 2, 5 C.C. of the solution of 6

~

lie 0.0. were taken. Tho rolume of invert sugar solution employed was 20 C.C. Tho amount of orgnnic non- sugnr solution used was 10 C.C. The following nra tho results :-Solution without non-sugnr, not pmclpitated by lend=D4-1V V. ; solution with non-su nr, and prc- cipitntcd by lcad=94*Ua V. The amount of lcnd solution used wns sonicwhnt in riccss of that required to complete clnrificntion. Thew results show thnt, in the caw of cnnc juices nnd the ordinnry run of Muscovndo sugars, the optical netivity of thc constituents is not likely to bo affected by clarification with basic lcad acetate when csccss of that rcngrnt is nvoidcd Further they bcnr out thoso of Hornc in showin thnt tho lend precipibtc docs not absorb sugar from &e solution. I n this con- ncction i t ma bo nientioned thnt, with cano juices 88 occurring in tze Lecwnrd blends, i t is a simple mntter to judge when a sufficient qunntity of lcnd solution hns lwcn nddcd to the juice, as a slight CXCCLW of the reagent invnrinbly produces a greenish tint, owing to tho presence in the juac of cmnll I unntitics of a body which function8 ns on indicntor. yietding yc~owisli grccn bodies wit11 nlknlis. (It is a soniewvhnt curious fact thnt such nil indicntor should exist in cnnc juices, ru most of tho usunl indicators give precipitates or colorirlcss solutions with this cornpoiind.)

-4s rc$nr& the caw for niol~sses i t nppcnm thnt thcrc is linbility to a smnll nmount of crror unlcas very grcnt cam is token to avoid cxccss. In cooncxion wlth thk

uestion, nttcntion niny be cnlled to tho ciccedingly Jivcrsc nicthods nt prwcnt prevniling in the simple polnrinietric rending of rnolnsscs. Be far as can bc axcrtnincd, the most u a ~ a l incthod with low grade products of thir dwcription is to weigh out the noruinl wci rht, dissolvc it in wnter, add between 20 and 30 C.C. of basic lend ncctntc solution, mnkc up to 100 c.c., filter, and polnrisc. 'I'hb proccss involves lnr o errora owing both to the cxccssivc volume occupici by the prccipitntc, nnd nlso to the reaction of the excess of lcnd with tho Inrgc amounts of lcvulosc contained in tho

furthcr. We Iinvc therefore dcviscd u niodificntiorl of Allen's motliod \chic11 we think is LL considernbly ncnrer '

- solution. :. Another iucthod k thnt given in Allen's Colunicrcial Organic dnnlyais (Vol. I, p. 267, 3rd cd.), wlicrcin n doitblc norninl weight is tnkcn, dissolved in wntcr, tiallv clnrificd with bnsic lcnd nccttrtc and sodium suII)11% xoluiions, mndc up to 100 C.O. and filtered ; of tlic fikrnto 50 C.C. nro tnkcn Hnturnted with sulphur diosidc, nindc pt to ion c.c., nnimnl elinrconl nddcd, filtered and polnriscd. IKis method is linblc to serious crrors nlso, by rcRHOJI of precipitate \*oluniea.

I n our expcricncc wc haro found i t iriipoasible to clarify niolnsses solutions by iiiennu of the sini Ic nddition of dry bnsic ]cod acetate, since tllc salt rnp i iy ~wconics coated with insolablo nintter nnd refuses to disolvo

Defecnkd with 26 C.C.

No. I solution and mnde up to 100 C.C.

. bnaic lend acetatc

Tlic nbove results show a difference bctwcen the two methods amounting, on tlic average, to about 3” Ventzkc, and cniphnsise tho extreme niagnitudo of the errom likely to nrisc from tlic eniployment of defective mcthodr, with products of this clnss.

In connection with tho qiiestion of the actual mechnnisni of the process of clarification with bwic lead acetate, it ap anrcd to us tlint i t might be of some intercwt if Hoinc inEormatioii were fortlicoming tlR to the composition of the precipitate obtained in clarifying can0 juices, and nccordingly the amount of lead oxide contained in tho precipitate froin the j uice of five different West Indinn cnne vnrietier, gown in Antigun, wns determined. The

rccipitatev IVCTC obtained bv trcating tho juicm with Ensic lend acetate ,nolution df the iisual strength ; no R cia1 selection of, the cnnes wns ninde, they being simply c L e n haphazard during the course of the nu nr cnnipnign ; the rccipitates were wnshcd with distilfed water till freo from sugar, ns judged by tho n-nnphthol reaction. The nniount of lend oxide contain4 in thein WOH deter- inined by the method givcn in Frcsenius’ Qunntitiitive Annlysis (Vol. I, p. 246, ed. VII.).

Tlie followiug results wcro obtained :-

Drfeeated with dry bnsic lend ncetnte

md sulphur dioxide. (New metliod.)

I X O .

1 2 3 4 61

Lend oxide in the precipitntc. I Vnricty.

Per cent. Ilurkc 51.2 1). 035 53.3

Whito Trniiqinrcnt 51-8 Bft. IIlnnc 53.4 Bed Rlbbun 52.7

I I

Ncnn I

59.08 __

---I__ _. -____ --___-- . . found to resent a similar phenoinenon It theroforo ‘appxred t i a t ’ tho effect obscrved is duo to some con- ntituent. or constituents, normnllv occurring in cane juices in Antigun. A considern6le quantity of thin prcci itate wne propared from tho residues of juices clnriffed for hriaation during tho last nugnr campaign, the prncticc E i n g to tramfcr the clarified rcnidiien from each dny’s work to a large hnkcr ,ndd sufficient bnsic lcnd acetate nolution thereto to effcct precipitation, allow the precipitato to subside over-night, and in the iiiornin pour off the clear supernatant liquid and half illf thc bcnkcr up with water; the next day’s residue8 werc accumulated in a similar manner, nnd RO on. When n nuficient quantity of this precipitate had been collected, i t wwi filtercd nnd wnshcd with distilkd wntcr till freo from Hiignr ns judged by thc a-naplithol renction. A portion of this reci itato was (111s nded in wnter and tleconipcd w i i Hurphurctted 11 ygogcn, tile resulting soltition ot organic niatter k i n g conccntrnted to small bulk on’ tlie wnter bath, as dcs- cribed in respect of the priinnry lend precipitate. The sohition obtained wns prncticnllg colourlcss. With moderate ninoants of acid, alkdi or nlcohol, this solation did not vicld n precipitate. With Holutiow of brwic lend acetate, ‘a flocculent, coloiirless prccipitntc wtw a t once obtnined, but soliition9 of neutral lend ncctirto occnsioned no precipitation. Evaporaton of tho solution to dryness showed that very m o l l quantities of organic matter were obtained from ielutivcly largo niiiountv of the lcnd compound. The amount of lend oxide contained in the lead precipitato wns dctcrmined by the method given above for tlie prininry precipitate, and sns found to bo 81.03 pcr cent., an nmount differing very slightly from tliat cnlculnted for basic lend ,ncctnte itself.

From thc nbove obdervntions i t would upl’cnr thnt tho nubstance is probably relnted to pcctin. It would n p p a r like1 thnt its prexencu in cane juice mny he wcounted for {v solution in thc juice of rtion. of tho v ~ g e t a b l ~ cclhi of the cnne, which arc &upted by the process of milling, nnd ono would, in consequence, expect to find hrgcr ( unntities of i t prcfient in jiiicca obtained in factories whcm keavy milling and mnccration nro practised, than in juices obtained from lighter mills. (Scc l’rinscn- Gccrligs.

As to thc presence of lead in the clnrified jnice, tlic only feasible explanntion, so far as wc can see, is that the slight ncidityof the cnno juicc is sufficient to ncutrnlinu the iilkulinity of n portion of the bnsic lcnd ncetate, which is thereby converted into ncutral lend salts, Home of which may be precipitated and the rciiiaindcr rcninin in solution. That thcne lend xnlts nre not. rciuoved from solution bv combination with tho prccipitablc matter prcscnt &, we think, due to the fnct that tlieru in alrcndy a sufficicyt quantity of tlie bnnic salt present to removo tliiN. ‘l’his phenoiiicnon is not shown to neurly H U C ~ n niarked extent in juiccs which have been clnrified with limo in tlie proccsx of riinnufucturc, or with tho majority of raw H U ~ I I I W , though i t io true that i t is niarkcdly cvidunced in somo cnscs, and in niost others Hliglit evidences appear on standing.! It would HCCIU, tlicrefore, tlint tho heating of limed juicc in clarifiers, dcfecntom, and eliriiinntom removes niuclr of this interesting impurity.

Having observed that lend is noriiinlly present in lend-clnrificd juices, i t rcinnined to bo seen what effect, if m y , i t could have on tlio subsequent nnnlvtical operations. To begin with, if prcscnt ne tho neutral icctate, i t would not bo likoly to allcot the opticnl nutivity of any lcviilwe prcscnt, wince, UH Jins hon show in the prescnt ~ i u p r , tlie cliect of bush lead acutntc on tlic opticnl activity of ~ovu~one is occnaioncd by the bnsic portion of thut snlt, and is not duo to tlic action of tho neutral compound.

Tho next point to bo iliWHtlgIIkd wtu whctlicr iiiiy effect could k exerted on tlie dotarininntion, by Fchliiig’s solution, of tho reducing sugnrn present in cane juice. It is a eoninion practice nmong sugar houso chemists to pcrforni tlic dctorniination of tho reducing sugars by Fchlinp’H solution on the 1end.clnrified juico ; i t hnH, however, been the practico in thin laboratorv to perform tlie test on tho raw juicu without clarilIcation. In vkw of this, i t nppenmd dcsiruble to us to anwrtnin what ditrorcnces; if uny, existed botween tho reducing

The Sugar Cane, 80, 91 and 124).

sngnr contents of cnnc juiccrr ns determined on tho raw and clarified juictw reapcctively, c~~pecinlly so a~ clnrificd juiccrr hnvc h e n nhown to contain load snl ts in solution and i t is known that the pmencc of lend in solution is linblc to affect tho vnlidity of the Fchlin determination, (Sec Tucker, 8fnnrinl of Sngnr Annfvnis, 18W ed.. p. lo&) Accordingly such n scries of determinations wy undertaken during the eoumc of the l a ~ t wugnr cnni- pnign. Tlic dctcrminntions xverc rrformcd by the volumetric procesn ; tlic nctnnl nictiod employed will bc described in a nrihcquent p i s r . 10 C.C. of Fehling's tiolntioii werc used in each cnne. I n one series, the deter- ininntion wnti perfornicd direct on tho rnw juice, nnd in the other on n qiinntity of thc snnic jnicc clnrifiecl by nienns of anhydrous bmic lend ncctnte. Thc rcsiilts werc as follows:-

Kame of No. cnne variety.

1 I Wliito Trniia-

2 dn%:nC 3 Sled Itibbon 4 Durko 5 Senlv Ycrdling 0 ji. 508 7 u. 1756 8 D. 130 0 I). 110

10 I). 05 11 1 I). 74

Dillerencc. -_I_

--O.oin -0.0:io -MI03 -04% -0.019 + om?

Prom the nhovc resnlts wc see that there is i in nvcrnqo dilicrencc in tlic redueins s u p contents in favour of tlic rnw juice owr tho clnrihed juicc amounting to 0.016 per cent. Tliis nniount is R O wino11 thnt i t is of no grent iniportnncc in nctnnl practice in connesion wit11 (WIG

juice, and from the titandpoint of imcticnl siignr clicinistry i t uplwnnr thnt i t is iuuiintcrin1 whct~icr t ~ i c deterininntion is Iicrfornied on rnw or clnrilicct juice. -4s i t liar h e n shown, ho\vever, that sinrill quantities of lcnd do occur in tlic clnrifed jnice, i t li~conics wortliv of enquiry ~vlietlicr tlic aniount of ~cait Iircsent in tIic 'juice \VIM sufiieient to account for the oliservcd sninll dilicrcnces bctwccn the reducing sugar contents of rnw niid clnrilied juices.

Kqiiol qunntities of tile invert solution nlrcndv refcrrcd to wcrc iiinttc iip to u standard IiiiIk of 100 c.r: witti tile nddition of increiwingly large nnioiints of Iinnil: Icntl ncetnte solution, nntl the nppnrcnt rcdnciiig s u p r conti!nts wore cleterniinetl by iiieiins of titrntion ngnmst 10 C.C. of Fcliling's soliitioii. 'I(1icsc solutions rcnininctl briglit on the nddition of the lcntl solntioii, witli the cscelition of So. ti, \vliere II sliglit tnrbitlity nlijn~ureil. clue in 1111 1)robnhility to tlic cnrhiatntion or Iiyclrolyin of tlic Ilntiic l~ortioii of tho lend anlt. The rcsirlts nrc given I)ClO\V. - .I--_ -. . - ~

! 1lW5 10~1 0.541

.'.I)

11.1 w50w -- ~ .. E'roni tlie ul)ovu rcsiilts ivc see thnt,, 011 tlic avcrn w,

tlic prescnce.of I c.c. of tJnsic lend ncetutc fioliition of tSi,c strength coniinonly ~irililoycd id urinlytiuul ~irnutice IS ecluivnlcnt to tlic nppareirt reinoval of 0 . 0 0 ~ grin. inn c.e. of reducing niignr from tlic solution, u1icl tt$i to occiision nn cffect eqnnl to tlint oliacrvctl in tho c n ~ e of nctnnl olnrificcl cnnu jniccs \vould rcquire tlie ~irescni:e in the juicc of nil esccss of Ieud cqunl to tlint contuinetl in tit hist 2 e.c. of bndc ,leud acetate Muhition. It niiy lu, stated that tliu totnl nniount of Icutl sullltion rcqirirrtl to uffcct clarification, voly rurely oxceods tliiri unioiint, m d uti thu grcntor part of tho lend oppeun ia the pro.

cipitate the amount remaining in the rrolution must IJC fnr below t.his. \Vc nre, therefore, forced to concludc that the excess of lend present in the clnrified jiiicc is not responsible for the small diffcrencc obwrvcd, und thnt this is rnthcr owing to thc rcmovnl of a nninll nmoiint of sonic rcdrlcing subntnnce in t,hc cownc of defecation with busic lend ncctnte. Of whnt this tinbtuncc, or siihtnncm, consiRt \vc cannot R U ~ ; thnt i t is not eithcr clcxtrosc or lcvulosc nppcnm certain from the rcsiilts descrihd in this palrr. It ctocs not nppenr improlinblo to 11s that the organic non-fiu wr removed from tho jriieu niny contain, however. obscurc?iodies capable of nffecting tlie dctcrminntion by thc ainonnt observed.

In tlic coiimc of this p p c r no mention lisn bcen nindc of thc possiblc rffcct of bnsio lend ocetutc on thc specific rotation of sticrosc itHClf. F. Bntcs and J. C. Blnkc huvc rccently brought forward thc rcniiltri of cspcrinicntcr rnndo by thsm in tlijs direction (&its. Ver. f. Ibuk9. %iickcr Ind., 1907. J14-323; J. Anicr. Cheni. SOL, 1007, 29, f8U-%3; this J.. 1907, 333, 541). Tliesc workem find thnt ncltlition of ~ninl l qnantitics of bnsiu lend ncctnto tiolution, fi I. gr. 1.25 (from 0.5 t o 2.0 c.c.) to n 2 ( i . t ~ p r cent. solution of purc cnnc nugnr. cuused n progrennive rcdnetion of the polnrinieter rending (tho rnnsiniiiiii rednction bcing wlightly over 0.1 p"r cent,.) ; with larger quantities of tho rengent (from 2 to 0 c.c.) tho reduction hcutnc Icsa ; tho solution to which U C.C. of bnsic lend ncctntc hail bccn ndded gnvc tho xnmc polnrinicbr rending UY onc to which no lead lincl bcen nddcci : nddition of till lnrger qllnntities of bnsio lend ncetnte (froni 7 C.C. to (13 c.c.) caused D progressioo incrcnsc of the polnriincter reudipg (Ilil1SilllllllA nboiit I 1wr cent.). According to I%ates ond Jhke . " tliu inllitencc of tho bnsic lGnd ncctntc npl'cnw to bo duo to tlic forinntion of solublc lend $acchnrcites tinring rotiitory powcrs clitiercnt from thnt of tiucrose." According to thesc results, sninll cscesscs of lead wonlcl olrriitc in n contrnry dircctioli to tl iut in wliich they do 0 1 1 invert sngur, nnd hence the two eficcta woi~ld tend to ncirtruliso onc nnother.

Onc point in o w obscrvntiuw ~vliieh 111) wars to niilitnte somenlint. nguiiist tlic tlieory of Untes i ir ib~lnkc reguriling tho forinntion of R noliiblu lcntl sncrlisrnte, is tlint with norninl soIutiorw of pure tiucroso wo huve nlanys foillid tlint tinsic leiid nwtntc, when ncltlctl tlicreto i i i nniull qimntities, invnrinbly prodnces turbidity on tihort stnntl- ing, dnc, in our opinion, to cnrbonntation or hydrolvsis* or t l ~ o Iinsia portion of ttio salt, ; on tho other Iiutici with solnt,ionn of invcrt siignr, \rheru IL so111bla lead Icvnlmntc is nndonbtcdlp fornicd, tliroi~gli thu inter- iictiori of lcritlo~c with tile biisic ~iortion of the lend anlt, no siicli turbidity in eslwriciiced.

f h i c r d Co,rrltrnir~/rx.--To put the 1nuttc:r brii!fly, wc Iiavo nrrivccl at thc: following C O I ~ C I I I S ~ ~ I W :-

I . Jhccwivc~ nnionnts of bnsic: Icstl ncetnte cscrcisc nn nlqircciiiblu ctiect 011 tliu optical i1etivit.y nntl reducing p o w r of solutions of inverb t in~nr .

2. i\'Iicrc csccss is trvoitlcd. hid i t cusily is nvoidcd in nnnlpticnl prncticc, clurification by Incuns uf dry nnliydrous basic lend ucotuto involves no np~iroeiiiblc error.

I n thu cnsc of low gratlo Iiroduuts, snch UY second niolnsscs, n grcnter nplroncli to' nccitrncy tlinn tlint iisunlly nttnined. is Kot by clnrilicntion witli dry l~nsiu lead acetntc followcd by siilpliiir diosidc. unrl this is cdpciully so with rcgnrcl to dcterniinntions by the Fcliliiig Inutllotl. In view of tliiw results, it n1i m r s iimicci!ssary to

Rcurcli for iiioru coinli~iccitet~ iiiotliotls of clnritication, for tlie IISC of solid nriliytlrous lead neutirte gives results wliiuli nro ivcll wit hi^^ tho limits of nccilrauy of ordiniiry methods of nnulysis.

I~rsoussroh-. Mr. Jtl l~l ,%N L. BAKE^^ tinid tho niitiiora w r o to lib

uongrcrtulutcd on tho niutitier in which thcy l i d clucidntcd ninny obecuru points in tho IIHO of leiid ucctuto ns n dofccation ngent for nirgur suliit.ioiw. Tho Iituratiiro on thc siibject WUH volun~i~iouu und tho opinions of dilTerciit inventigutonr worc coiitradiutory. 150 \van not nwuro

.in uxuetlyslriiilur ~i~i~riuwc~oo b U ~ I U W I I UII dilutlolt r i t l inrter . __ ___-----.

68 SKIRROW-THE DETERNINATION Oh' PHENOLS IN GAS LIQUORS, &c. [Jnn. 31, 1008.

in rnw sugnrs, M tlierc \vns u linliility for secontlnry reactions to occur. I'crsonnllv, hu never liked to curry out inversion a t a teni wrniure Iiiglirr tiinn i W L'. ; 6 t o 10 minutes wits nnil'fe time in rill cnsw, 5 minutes

tha t other clnrifying ogcnts such ns ph&pho-tungstic mid had ever k e n employed for xiignr solutions. This acid coultl In? used with nnfcty for palo nnd tlnrk worts and for cnrnniels, nnd lie would suggest thnt it niight k worth considerntion bv sugnr chcniists.

31r. E. CILAST How& regurded the riddition of nnhydrous basic lend ncctnte ns n distinct iniproveincnt on t.hc use of n solution. It scenicd to hiin thnt in ninny case4 there wns n tentleiicy to U H D too strong ncid for the inversion of siignr, nnd to iindulv prolong the periotl of inversion. It woii~d generally SK found tlint n four ininutcs' boiling with 6 c.c.'s of Iinlf-norinnl Iiytlrochloric ncid clfccted coinplctc inversion of ennc siignr. nnd hncl no nction on other cnrbolivdrntiw present. He uuder- stood t,hnt the nuthorn cirricd out tiit! invrrsion for I5 niinutcs, Iiut nt IL lower teniperntiire, In II Inborntory devoted to the nugnr inchistry, nrrnngeinents \vould lie tloviactl for carrying on invcrsioiis tit tenipornturcs con- .trolled by II thcrniostut, nnd no criticisin need IJC of lerd of sue11 prnctice. bu t wliere occnsionnl siignr invemiotis wcrc k i n g innde lie thought i t ivus nn ntlrnntnye to carry out thc opcrntion in tho shortest tinw. ant1 under direct pponnl supcrvision.

F. I % I I I ~ Q Y mid lie thoiiglit the niithors hlievctl that the nlknlinity of the lend solution occnsioncd tho notion on the rotnry po\ver of lcviilosc, nnd it FILS quite rcwonnblc that tho nddition of n fcw drops of ncctio acid to tho liltercd solution woiilcl snve the trouble of romoving tho lend froni the solution. lh i t with rcgnrd to the w e of eolid basic lcnd ncctnte, i t scienietl to hiin it was n qucrition of whnt other pcoplo were doing. If soniconc eke, ivhouc unnlysis wns going to h coinpiiretl with 0110's own, ured tho solution, nnd one used the solitl acetate, it did not nintter which \vus tlic more ncciirntt*, tho pricc wna fixed by whnt wns ~isiiiilly done, nntl if such nn nltcrntion \vus going to bc ninde, i t would have to bc mndc by the consent of nil the clicniists in tiit! industrv.

Dr. L. !l'. 'L'iioitsi: said lie knew i t \vns n eoninionly ndoptcd plun now to boil the solution for iiiveision for a short tiine. but nlthouali thnt inicht k suitnblc with

Jlr.

i n these tlirca distilliitcs, ii control test Iinving slio\vn tliut. the unioiint of plienol in 11 fourth clistillutc ivus iiegligiblc. 111 ortlur to gut ritl of iiny iicitl wIiicli I IUS clistilletl over, nncl wliicli woiilii upset tlic subsequent

tho one used by Korn for tho estitnntion of phcnol in offfuonts (Zcits. unnl. Cliein., 3006, 46, 6G2). This is bneed on tho volunictric nicthod of Blcssinger mil \'ortintinn (Der., 22, 23313 ; Zrita. unnl. Clicin., 31, 220). See crlso Kosder iind l'unny (Zeits. phyniol. Clicni., 17, 117). In nliplying the nietliod to gns lirliiors ccrtnin niodilicnt ions lire I I C ~ C H S I W ~ in order to ohtnin rclinblu results, rind i n the following tlic inotliotl so nnicntlctl is dcscribetl.

The phcnol is tlistilletl oli \villi wntcr nncl then convrrtctl into tri-iotlophenol by niciiiis of nn cseess of iodine, wl!ieli is titriitetl Imck with tliiou~il~ilintc.

Tlic reactions involved nrc tho following :--'LNtrOH + 21 = XnIO + SnI + H,O. ( I ) ; C,HGO€I + 3NnIO = C,H,I,OH* +:%NnOH. ( 2 ) Tliefio rcnctions nrc cquivulcnt ~ O : - L ' , N ~ O H + ( ~ I = C , H , I ~ ~ O I ~ + : % H I . On ncitlificiitioii tliu following renction tiikcs pliicc :-S1110+Sn1+

iuiused iodinu is set free und cnn be titrnted. Tho following precnutions inuut be ntloiitetl :-(I) Sulpliiirettctl hydrogen nntl sulpliitles niust first Im rcniovetl. (2) Jiydro- cynnic ncitl ant1 cynnitlrs iniist bc oliininntetl. (3) On cvripornting 1110 liquor it inust lie per~i~nncntly nnd strongly nlkrilinc.

100 C.C. of tho filteretl gns liquor in lirst trcntetl with i i n osccss of uniinoniiiiii po1ys11l~ihitle to convert nny cynnidc prescnt into t l~iocy~~natc. This is idlowed to stnntl. nntl tho solution tlien nindo up to 200 e x . 'J'liti sulphides tire then precipitntetl. niost, conveniently by Icntl eurlioniite, untl tho Icncl siil ihitlc nnd tho esccsx of leiicl crirl)onnto Iilteretl on. A n cscess of sotliiini lydrosidu p25 C.C. of 50 per c u t . solution) is then iidtletl to IOU C.C. of tho filtrrite, und 1110 solution cvnporntctl until the snltti hegin to selinrntu out. 'l'lic rcsiduc is wiislicd into ti litrc tlistilling lliisk nnd diluted to nlioiit 150 C.C. with ilistilletl wnter. niitl ivhen cold is iicidilietl with aulphiiric noid. The liquid is clistil!Fd until tlic siilts begin to crystrillise out ; \vc thus obtnin distillntc I ." 100 C.C. of wnter is udclcd to tho ilistillinc flask. mil tho

HZSO, =I,+XCI,SO~ +HZ0 i 1 n t l l l l l lR the \VIIOIC of t l lu

clnrilicntion IJV unliyclroiis Iiusie lcnd ncc:tatc \vas $own to IIC the Iwst, IIS it scerneil to IIC n~io\vn now, 111 getting tliiit ~irocess ncloptetl generally. Of coiirsc thCHl! dctcrininutions \verc of w u t iniportuncc froni tlic aoniinerciu~ point of vicw. keeiiusu, wit11 the liirgc duties on sugnr in varioiis cotintrier, espciully in Aniericu, n differenco of 0.2 or 0.3 jm cent. on nn iniportntion of 5,000 or 10,000 tons would run into lnrgo figures, and thcreforo it Hns necessary to haw uniforniity of nnulyticul methods. - - . . . . . . .

Manchester Section. Jeel i i lg 1 d d cd .lfuircLeutcr, o t ~ Yridciy, ~ ! ~ c c o i i b e r W I , I i I O i .

---- ---

3111. 11. 11. CLATTOS IS TIIE 011AIII.

woiims. AN^ TII k: i > iwr i? . i i i i i * i - inw nw Q I W W

--- TH15 DISTIWILINATIOS OF PHENOLS 1N GAS

It ~ v u s fount1 thut if cyiinitle were prcwnt, tlic Iiydr~i- cyiiniu iiciti wliicli tlistiIlcti over on tlic iirst sut of clis. tillutions \vus not, retuineil by tliu culciuiii cirrbonntc, iind thus piisset1 into the finnl clifitilliitcs. iind euusccl too lurgc 1\11 nniount of iodine to I J ~ titken up. 111 tliu eliso of tliiocynnntc, Iiowcver. it \viw foiind that tliu tliiocyiiniu iiciil which tlistilletl over, being u stronger iicicl tliun Iiydrocyirnic neitl, \vns priicticnlly coiii~ilotely ratnineti Iiy tho ctilciiini enrlioiiute. l'liiis, on couverting tho cyiinitlo into thiocynnutu i i l l troiiblu on this seoru \vus iivoitled.

'l'hc titrntioii of the l innl clistillutir WIIS cnrrietl o i i t 11s follow :-IOU e x . of the unitetl tlistilliites w i i s ~ i i i i t l u iilknlino with sotliiiiii liytlrosidc nnd \viiriiicd to (i0" (1. An usccss of iotlinu ivus tlicii riin into tliu Ilusk, which \vus i l l l l l lC~i l l tC~Y u ~ o l l l l u r e ~ ~ 11111~ iIjlo\vctj lo cool \\.itil frut,llulit sliiikiiig. ' I l iu coiitents wuro tlion titrutctl buck \vi l l i S/10 sodillin tliiosul~ilii~tc ufter ucidifying tlie liquid, stiireh being used us indictitor. Tliu onit point is innrkccl I)? tl1y Jrlillsitioli fro111 blue to (I ray ,pink. .I!. y,e!l

1 I , * .