Sulfurated Potash

Thiosulfuric acid,dipotassium salt,mixture with potassium sulfide (K2Sx).
Dipotassium thiosulfate mixture with potassium sulfide (K2Sx) [39365-88-3].
»Sulfurated Potash is a mixture composed chiefly of potassium polysulfides and potassium thiosulfate.It contains not less than 12.8percent of sulfur (S)in combination as sulfide.
Packaging and storage— Preserve in tight containers.Containers from which it is to be taken for immediate use in compounding prescriptions contain not more than 120g.
Identification—
A: To a 1in 10solution add an excess of 6Nacetic acid:hydrogen sulfide is evolved,and sulfur is precipitated.
B: Filter the mixture from Identificationtest A,and add to the filtrate an excess of sodium bitartrate TS:an abundant,white,crystalline precipitate is formed within 15minutes.
Organic volatile impurities,Method IVá467ñ: meets the requirements.
Assay for sulfides— Transfer 10to 15pieces of Sulfurated Potash to a mortar,and reduce to a fine powder.Transfer about 1g of the powder,accurately weighed,to a 250-mLbeaker,and dissolve in 50mLof water.Filter,if necessary,and wash or dilute with water to 75mL.Add,with constant stirring,50mLof cupric sulfate solution (1in 20),and allow the mixture to stand,with occasional stirring,for 10minutes.Filter through a retentive filter,and wash the precipitate with 200mLof 0.25Nhydrochloric acid,taking care to avoid breaking up the cake.(If the filtrate is not blue in color,discard the assay specimen,and start over,using a larger volume of cupric sulfate solution.)Ignite the precipitate in a tared dish at 1000for 1hour,cool in a desiccator,and weigh:the weight of the cupric oxide so obtained,multiplied by 0.4030,represents the weight of Sin the specimen under assay.
Auxiliary Information— Staff Liaison:Karen A Russo,Ph.D.,Scientist
Expert Committee:(PA1)Pharmaceutical Analysis 1
USP28–NF23Page 1579
Phone Number:1-301-816-8379