Product Knowledge Article

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.

According to the principle of acid-base neutralization reaction, methyl red-indigo mixed solution was used as the indicator, and the titration was performed with hydrochloric acid standard titration solution until the solution turned red as the endpoint.

In the sample, ammonium bisulfite is oxidized to ammonium bisulfate by hydrogen peroxide. Then, using methyl red-indigo mixed solution as an indicator, titration is performed with sodium hydroxide standard titration solution until the solution turns yellow-green, which marks the endpoint. The mass fraction of ammonium bisulfite is calculated based on the consumption of sodium hydroxide standard titration solution.

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 0.40%.

In neutral or weakly acidic solutions, iodine oxidizes ammonium sulfite and ammonium bisulfite in the test solution to ammonium sulfate and ammonium bisulfate, respectively. A starch solution is then used as an indicator.

Solid ammonium sulfite should meet the requirements of Table 1.

Warning—Some reagents used in this standard are toxic or corrosive, and certain operations carry hazards. This standard does not disclose all potential safety issues. Users must strictly adhere to the relevant regulations for proper operation and are responsible for implementing appropriate safety and health measures.