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 100mg of Sodium Sulfide,to a suitable container,add 10mLof 3Nhydrochloric acid,and cover the top of the container with filter paper saturated with a 0.2Mlead acetate solution:a brownish or silvery-black color forms on the paper.

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

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

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

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 1794

Phone Number:1-301-816-8394