YS/T 910-2013Determination of copper content for brass. lodimetry (English PDF)

3.10.1 Preparation

Weigh 250g of sodium thiosulfate (Na2S2O3·5H2O). Dissolve in a 1000mL beaker. Add 2g of anhydrous sodium carbonate. Transfer to a 10L brown reagent bottle. Use freshly boiled cooled distilled water to dilute to about 10L. Shake well. Let stand for more than 10d.

3.10.2 Calibration

Weigh three portions of 0.30g (accurate to 0.0001g) of treated pure copper sheet (mass fraction is >=99.95%). Determine simultaneously with the specimen according to 5.3.1~5.3.4. Carry out a blank test along with the calibration.

NOTE: Processing of pure copper sheets: Put the pure copper sheet into slightly boiling glacial acetic acid (1+4) and boil for 1min. Rinse twice with water and absolute ethanol after removal. Bake in a 100°C oven for 4min. Cool down. Store in a ground-mouth reagent bottle for later use.

Calculate the actual concentration of sodium thiosulfate standard titration solution according to formula (1):

Where,

c - Actual concentration of the standard titration solution of sodium thiosulfate, in moles per liter (mol/L);

w - Mass fraction of copper in pure copper sheet, %;

m - Mass of pure copper sheet, in grams (g);

V1 - Volume of sodium thiosulfate standard titration solution consumed by titration of pure copper solution during calibration, in milliliters (mL);

V0 - Volume of sodium thiosulfate standard titration solution consumed by titrating copper blank solution during calibration, in milliliters (mL);

63.55 - Molar mass of copper, in grams per mole (g/mol).

3.11 Parallel calibration

Conduct parallel calibration in triplicate. When the relative error of the measured value is not more than 0.1%, take the average value; otherwise re-calibrate.

NOTE: The sodium thiosulfate standard titration solution must be re-calibrated every other week.