M297

Hydroquinone, C6H6O2M(C6H6O2) = 110.11 g/mol, z = 2

Hydrochloric acid 0.1 mol/L, Fluka

Cerium sulfate, c(Ce(SO4)2) = 0.01 mol/L

T50/70/90XS205 Balance

C6H6O2 + 2Ce4+ = C6H4O2 + 2Ce

3+ 2H+

Glass beaker, ME-101446Olivetti JobJet 210 PrinterLabX 2.52SP250 Pump, ME-51108016Additional Dosing Unit, ME-51109030

METTLER TOLEDO

Hydroquinone: Evaporate solution, special wasteCerium: Precipitate with NaOH and filtrate,

special waste

Wastedisposal

Preparation and ProceduresHydroquinone, C6H6O2c (1/2 C6H6O2)= 0.05mol/L: 1.5 mL

Sample

Substance

Chemicals

Titrant

Instruments

Results

Chemistry

Accessories

DM140-SCIndication

Factor Determination of Cerium Sulphate vs. Hydroquinone

- Place an empty glass titration beaker on the manual titration stand- 40 mL HCl 0.1 mol/l will be pumped in automatically- 1.5 mL hydroquinone will be dispensed- The sample will be titrated with cerium sulfate 0.01 mol/L using a

DM140-SC electrode

- Weigh 2.753 g hydroquinone in a glass beaker, transfer itwith deionized water into a 1 L measuring flask

- Add approx. 900 mL deionized water- Add 10 mL H2SO4 96%- Fill up to the mark with deionized water

- Pipette 50.0 mL of cerium sulfate 0.1 mol/L (Merck 1.09092.1000)in a 500 mL volumetric flask

- Add approx. 400 mL deionized water- Add 10 mL H2SO4 96% and gentle mix it- Fill up to the mark with deionized water

Theoretical consumption

- 1 mL hydroquinone, c (1/2 0.05 mol/l) corresponds to a consumptionof 5 mL cerium sulfate, c (0.01 mol/L)

Literature

- Application Brochure Gold and Silver DL67/DL70OES/DL77ME-724613

Remarks

R1 = VENDDi*0.05/(VEQ*c)C1 = 1

H[Cerium sulfate] = Mean [R1]

Calculation

Titration Excellence Line: The factor of the cerium sulfate solution will be used for the gold determination ofgold alloys and pure gold. See also applications M298 and M299.

Standard ----

Claudia SchreinerAuthor

Wastedisposal

1

Table of measured values

Start time: 22.03.2007Sample Data Note / ID Sample size No. 1/6 Hydroquinone 1.5 mL No. 2/6 Hydroquinone 1.5 mL No. 3/6 Hydroquinone 1.5 mL No. 4/6 Hydroquinone 1.5 mL No. 5/6 Hydroquinone 1.5 mL No. 6/6 Hydroquinone 1.5 mL

Results Note / ID Rx Result Unit No. 1/6 Hydroquinone R1= 0.9828 -- No. 2/6 Hydroquinone R1= 0.9822 -- No. 3/6 Hydroquinone R1= 0.9829 -- No. 4/6 Hydroquinone R1= 0.9832 -- No. 5/6 Hydroquinone R1= 0.9833 -- No. 6/6 Hydroquinone R1= 0.9836 --

Statistics Rx Name n Mean Value Unit s srel[%] R1 Factor 6 0.9830 -- 0.0005 0.05

Titration curve

Results

2

Method: M297 Factor cerium sulfate 05.04.2007User: Schreiner

001 Title Typ General titration Compatible with T50/70/90 ID M297 Titel Factor cerium sulfate Author Mettler Toledo Date / Time 05.04.2007 Modified at 05.04.2007 Protect No SOP None LabX SOP002 Sample Number of IDs 1 ID 1 Hydroquinone Entry Type Fixed volume Volume [mL] 1.5 Density [g/mL] 1.0 Correction factor 1.0 Temperature [C] 25.0 Entry Arbitrary003 Titration stand Typ Manual stand Titration stand Manual stand 1004 Pump Auxiliary reagent HCl 0.1 mol/L Volume [mL] 40 Condition No005 Dispense

Titrant 1/2 Hydroquinone Concentration [mol/L] 0.05 Volume [mL] 1.5 Dosing rate [mL/min] 60.0 Condition No006 Stir

Speed [%] 35 Duration [s] 10 Condition No007 Titration (EQP)Titrant Titrant Cerium sulfate Concentration [mol/L] 0.01Sensor Typ mV Sensor DM140-SC Unit mVTemperature aquisition Temperature aquisition NoStir Speed [%] 35Predispense Mode Volume Volume [mL] 5 Wait time [s] 5Control Control User Titrant addition Dynamic dE (set value) 8 dV (min) 0.005 dV (max) 0.2 Mode Equlibrium controlled dE 0.5 dt [s] 2 t(min) [s] 3 t(max) [s] 30Evaluation and Recognition Procedure Standard Threshold 500 Tendency Positive Ranges 0 Add. EQP criteria NoTermination At Vmax [mL] 10 At potential No At Slope No After numbered of recognized EQPs Yes Number of EQPs 1 Combined termination criteria No

MethodAccompanying stating

Accompanying stating NoCondition

Condition No008 Calculation

Result Factor Result Unit ---- Formula R1=VENDDi*0.05/(VEQ*c) Constant C= 1 M None z None Decimal places 5 Result limits No Record statistics Yes Extra statistical functions No Condition No009 End of sample

010 Auxiliary Value Name Cerium sulfate Formula H= Mean[R1] Limits No Condition No

3