Calcium Citrate
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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)
Ca3(C6H5O7)2 · 4H2O 570.49 CAS RN: 813-94-5.-A white, crystalline powder. Freely soluble in 3 N hydrochloric acid and in 2 N nitric acid; slightly soluble in water; insoluble in alcohol. To 15 mL of hot 2 N sulfuric acid add, in small portions and with stirring, about 500 mg of calcium citrate. Boil the mixture for 5 min, and filter while hot: the cooled filtrate responds to the identification test for Identification Tests-General, Citrate (191).
ASSAY: Accurately weigh about 400 mg of the salt, previously dried at 150° to constant weight, and transfer to a 250-mL beaker. Dissolve the test specimen in 150 mL of water containing 2 mL of 3 N hydrochloric acid, add 15 mL of 1 N sodium hydroxide and 250 mg of hydroxy naphthol blue, and titrate with 0.05 M edetate disodium VS until the solution turns deep blue. Each mL of 0.05 M edetate disodium is equivalent to 8.307 mg of calcium citrate [Ca3(C6H5O7)2): between 97.5% and 101% is found.
CALCIUM OXIDE AND CARBONATE: Triturate 1 g of calcium citrate with 5 mL of water for 1 min: the mixture does not turn red litmus blue. Then add 5 mL of warm 3 N hydrochloric acid: only a few isolated bubbles escape.
HYDROCHLORIC ACID-INSOLUBLE MATTER: Dissolve 5 g by heating with a mixture of 10 mL of hydrochloric acid and 50 mL of water for 30 min: not more than 2.5 mg of insoluble residue remains (0.05%).
LOSS ON DRYING (731): Dry it at 150° to constant weight: it loses between 12.2% and 13.3% of its weight.
Change to read:
ARSENIC (211)., Procedures, Procedure 1 (CN 1-JUN-2023): Proceed with 0.50 g as directed for organic compounds (6 ppm of As).
HEAVY METALS (reagent test): 0.002%.
