[marutikmv]

what is the assay method of sodium hydro sulfide

[Alberto_Kravina]

what is the assay method of sodium hydro sulfide

Huh? I don't really get that question.
Do you want to know how to detect hydrosulfite (Sodium dithionite) or do you want to know how to calculate the purity of the salt ?

[Mansouri]

Assay — Weigh accurately about 1 g, dissolve it in a mixture of 10 mL of formaldehyde TS and
10 mL of water contained in a small glass-stoppered flask, and allow to stand for 30 minutes
with frequent agitation. Transfer the solution to a 250-mL volumetric flask, add 150 mL of water
and 3 drops of  methyl orange TS, and then add, dropwise, 1 N sulfuric acid to a slightly acid
reaction. Dilute with water to 250 mL, and mix. To 50.0 mL of the dilution add 2 drops of
phenolphthalein TS and just sufficient 0.1 N sodium hydroxide to produce a slight, pink color,
then titrate with 0.1 N iodine, adding 3 mL of  starch TS as the indicator. Then discharge the
blue color of the solution with 1 drop of 0.1 N sodium thiosulfate, and titrate with 0.1 N sodium
hydroxide VS to a pink color: each mL of 0.1 N sodium hydroxide is equivalent to 3.482 mg of
Na 2S 2O 4. Not less than 88% is found.

formaldehyde TS: (30.03) and water

methyl orange TS: Dissolve 100 mg of methyl orange in 100 mL of water, and filter if necessary

phenolphthalein TS: Dissolve 1 g of phenolphthalein in 100 mL of alcohol

starch TS:  Mix 1 g of soluble starch with 10 mg of red mercuric iodide and sufficient cold water to    make a thin paste. Add 200 mL of boiling water, and boil for 1 minute with continuous stirring. Cool, and use only the clear solution

Best regards

[marutikmv]

Thanks -  mansouri

Assay — Weigh accurately about 1 g, dissolve it in a mixture of 10 mL of formaldehyde TS and
10 mL of water contained in a small glass-stoppered flask, and allow to stand for 30 minutes
with frequent agitation. Transfer the solution to a 250-mL volumetric flask, add 150 mL of water
and 3 drops of  methyl orange TS, and then add, dropwise, 1 N sulfuric acid to a slightly acid
reaction. Dilute with water to 250 mL, and mix. To 50.0 mL of the dilution add 2 drops of
phenolphthalein TS and just sufficient 0.1 N sodium hydroxide to produce a slight, pink color,
then titrate with 0.1 N iodine, adding 3 mL of  starch TS as the indicator. Then discharge the
blue color of the solution with 1 drop of 0.1 N sodium thiosulfate, and titrate with 0.1 N sodium
hydroxide VS to a pink color: each mL of 0.1 N sodium hydroxide is equivalent to 3.482 mg of
Na 2S 2O 4. Not less than 88% is found.

formaldehyde TS: (30.03) and water

methyl orange TS: Dissolve 100 mg of methyl orange in 100 mL of water, and filter if necessary

phenolphthalein TS: Dissolve 1 g of phenolphthalein in 100 mL of alcohol

starch TS:  Mix 1 g of soluble starch with 10 mg of red mercuric iodide and sufficient cold water to    make a thin paste. Add 200 mL of boiling water, and boil for 1 minute with continuous stirring. Cool, and use only the clear solution

Best regards