HG/T 2784-2012 Ammonium Sulfite for Industrial Use

4.2.4.2.1 Hydrogen peroxide solution: 3%, as specified in 4.2.3.2.1.

4.2.4.2.2 Hydrochloric acid standard titration solution: c(HCl) = 0.1 mol/L.

4.2.4.2.3 Methyl red-indigo mixed indicator: Same as 4.2.3.2.3.

4.2.4.3 Analysis Steps

Weigh approximately 0.5g of the sample quickly using the difference subtraction method, with precision to 0.0001g. Transfer the sample to a 250ml Erlenmeyer flask containing 15ml hydrogen peroxide solution (4.2.4.2.1) and about 30ml water, and shake well. Add 5 drops of methyl red-indigo mixed indicator (4.2.4.2.3), at which point the solution turns yellow-green. Titrate the solution with hydrochloric acid standard solution (4.2.4.2.2) until the solution turns slightly red, marking the endpoint.

4.2.4.4 Result Calculation

The mass fraction of ammonium bicarbonate (NH4HCO3), expressed as%, is calculated using formula (3):

……………………（3）

In the formula:

V — the volume of the standard titration solution for hydrochloric acid consumption (4.2.4.2.2) measured, expressed in milliliters (ml);

c-the precise concentration of the standard hydrochloric acid titration solution, measured in molar per liter (mol/L);

M-the molar mass of Ran Suanqing, measured in grams per mole (g/mol), with a value of 79.06;

m-the numerical value of the sample mass, in grams (g).

The arithmetic mean of the two parallel test results shall be taken as the test result. The absolute difference between the two parallel test results shall not exceed 0.10%.