HG/T2785-2012 Ammonium Bisulfite for Industrial Use

5.2.3.1 Preparation of Test Solution

Weigh approximately 5–6.5 g of the sample (with precision to 0.0002 g), place it in a 250 ml volumetric flask containing 150 ml of water, dilute with water to the mark, shake well, and use as the test solution for determining the contents of ammonium sulfite, ammonium bisulfite, and ammonium thiosulfate.

5.2.3.2 Determination

Accurately transfer 5–10 mL (depending on the concentration) of the test solution into a 250 mL Erlenmeyer flask containing 15 mL hydrogen peroxide neutral solution and 30 mL water, and shake well. Add 5 drops of methyl red-indigo mixed indicator, at which point the solution turns red. Titrate with sodium hydroxide standard titration solution until the solution turns yellow-green as the endpoint.

5.2.4 Presentation of Analysis Results

The ammonium bisulfite content expressed as a percentage by mass (X1) is calculated according to Equation (1):

……………………………（1）

Where: V1 — volume of sodium hydroxide standard titration solution consumed during titration, mL;

V2 — Volume of test solution aspirated during measurement, ml;

C-Actual concentration of sodium hydroxide standard titration solution, mol/L;

m — the mass of the sample, in grams;

0.09911-The mass of ammonium bisulfite expressed in grams, equivalent to 1.00 mL of standard sodium hydroxide titration solution [c(NaOH) = 1.000 mol/L].