HG/T 2784-2012 Ammonium Sulfite for Industrial Use
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- Jan 28,2026
Summary
In solution A (4.2.2.3) after ammonium bisulfite determination, add one drop of methyl red indicator (4.2.5.2.5). The solution turns red. Adjust to red with sodium hydroxide solution
4.2.5.3 Analysis Steps
In solution A (4.2.2.3) after ammonium bisulfite determination, add one drop of methyl red indicator (4.2.5.2.5). The solution turns red. Adjust to red with sodium hydroxide solution (4.2.5.2.2), then neutralize to just yellow with sodium hydroxide standard titration solution (4.2.5.2.3). Immediately add 10ml formaldehyde neutral solution (4.2.5.2.1), shake well, and let stand for 3 minutes. Add 5 drops of phenolphthalein-thymol blue mixed indicator (4.2.5.2.4), and titrate with sodium hydroxide standard titration solution (4.2.5.2.3) until the solution turns purple as endpoint.
4.2.5.4 Result Calculation
4.2.5.4.1 If ammonium bisulfite is present in the sample, the mass fraction of ammonium sulfate [(NH4)2SO4] (expressed as%) shall be calculated using Equation (4):
………………（4）
In the formula:
V — the volume of the sodium hydroxide standard titration solution (4.2.5.3.2) consumed, measured in milliliters (ml);
c—The precise concentration of the standard sodium hydroxide titration solution, expressed in molar per liter (mol/L).
m-the numerical value of the sample mass, in grams (g);
—The mass fraction of ammonium bisulfite, as determined in Section 4.2.2, expressed as a percentage.
—The mass fraction of ammonium bisulfite, as determined in Section 4.2.3, expressed as a percentage.
0.9850-the conversion factor of ammonium bisulfite [(NH4)2SO3·H2O] to ammonium sulfate [(NH4)2SO4];
0.6666-is the conversion factor for ammonium bisulfite (NH4)2HSO3 to ammonium sulfate [(NH4)2SO4].
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%.