Na2S·9H2O 240.18
Sodium sulfide nonahydrate.
Disodium sulfide nonahydrate [1313-84-4].

Packaging and storage— Preserve in tight containers, and store in a cool place.

Identification— [note—Conduct this test in a fume hood.] Transfer about 100 mg of Sodium Sulfide, to a suitable container, add 10 mL of 3 N hydrochloric acid, and cover the top of the container with filter paper saturated with a 0.2 M lead acetate solution: a brownish or silvery-black color forms on the paper.

Limit of iron— Dissolve about 5.0 g in 100 mL of water: the solution is clear and colorless.

Limit of sulfite and thiosulfate— Dissolve 3.0 g in 200.0 mL of filtered and degassed water. Add 100.0 mL of 0.2 N zinc sulfate, mix, and allow to stand for 30 minutes. Filter, add 1 mL of starch TS, and titrate 100.0 mL of the filtrate with 0.01 N iodine VS: not more than 3.0 mL is required.

Assay— Transfer about 275 mg of Sodium Sulfide, accurately weighed, to a 250-mL beaker, dissolve in 30 mL of filtered and degassed water, and mix. Add 50.0 mL of 0.1 N iodine while mixing, add 2 mL of hydrochloric acid, and allow to stand for 15 minutes in a dark place. Titrate with 0.1 N sodium thiosulfate VS to a pale yellow color. Add 5 mL of starch TS, and titrate with 0.1 N sodium thiosulfate VS to a clear endpoint. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium thiosulfate is equivalent to 12.01 mg of Na2S·9H2O.

Topic/Question	Contact	Expert Committee
Monograph	Behnam Davani, Ph.D., M.B.A. Senior Scientist 1-301-816-8394	(MDAA05) Monograph Development-Antivirals and Antimicrobials

USP32–NF27 Page 3585