Sulfurated Potash
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
Sulfurated Potash is a mixture composed chiefly of potassium polysulfides and potassium thiosulfate. It contains not less than 12.8 percent 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 120 g.
Identification—
A: To a 1 in 10 solution add an excess of 6 N acetic acid: hydrogen sulfide is evolved, and sulfur is precipitated.
B: Filter the mixture from Identification test A, and add to the filtrate an excess of sodium bitartrate TS: an abundant, white, crystalline precipitate is formed within 15 minutes.
Assay for sulfides—Transfer 10 to 15 pieces of Sulfurated Potash to a mortar, and reduce to a fine powder. Transfer about 1 g of the powder, accurately weighed, to a 250-mL beaker, and dissolve in 50 mL of water. Filter, if necessary, and wash or dilute with water to 75 mL. Add, with constant stirring, 50 mL of cupric sulfate solution (1 in 20), and allow the mixture to stand, with occasional stirring, for 10 minutes. Filter through a retentive filter, and wash the precipitate with 200 mL of 0.25 N hydrochloric 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 1000° for 1 hour, cool in a desiccator, and weigh: the weight of the cupric oxide so obtained, multiplied by 0.4030, represents the weight of S in the specimen under assay.
