Silicotungstic Acid, n-Hydrate
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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)
(Tungstosilicic Acid), H4Si(W3O10)4 · nH2O 2878.17 (anhydrous) CAS RN®: 12027-38-2.
Assay: Dissolve about 1 g, accurately weighed, in 25 mL of dilute hydrochloric acid (1 in 5). Add 50 mL of a solution of 5 g of cinchonine in dilute hydrochloric acid (1 in 2). Warm on a steam bath for about 30 min. Cool, filter through a tared crucible, and ignite at 800° to constant weight. The weight of the residue multiplied by 1.047 is equal to the weight of silicotungstic acid dihydrate in the sample taken. NLT 98% is found.
