Calcium Carbonate

Calcium Carbonate USP
CaCO3 100.09Carbonic acid, calcium salt (1:1)
Calcium Carbonate, dried at 200 for 4 hours, contains calcium equivalent to not less than 98.0 percent and not more than 100.5 percent of CaCO3. Packaging and storage— Preserve in well-closed containers. Identification— The addition of acetic acid to it produces effervescence (presence of carbonate), and the resulting solution, after boiling, responds to the tests for Calcium. Loss on drying— Dry it at 200 for 4 hours: it loses not more than 2.0% of its weight. Acid-insoluble substances— Mix 5.0 g with 10 mL of water, and add hydrochloric acid, drop wise, with agitation, until it ceases to cause effervescence, then add water to make the mixture measure 200 mL, and filter. Wash the insoluble residue with water until the last washing shows no chloride, and ignite: the weight of the residue does not exceed 10 mg (0.2%). Limit of fluoride— The limit is 0.005%. Arsenic— The limit is 3 ppm. Barium— A platinum wire, dipped in the filtrate obtained in the test for Acid-insoluble substances and held in a non-luminous flame, does not impart a green color. Lead —the limit is 3 ppm. Iron— To pass the test Mercury— the limit is 0.5 µg per g. Limit of magnesium and alkali salts— Mix 1.0 g with 35 mL of water, carefully add 3 mL of hydrochloric acid, heat the solution, and boil for 1 minute. Rapidly add 40 mL of oxalic acid TS, and stir vigorously until precipitation is well established. Add immediately to the warm mixture 2 drops of methyl red TS and then 6 N ammonium hydroxide, drop wise, until the mixture is just alkaline. Cool to room temperature, transfer to a 100-mL graduated cylinder, dilute with water to 100 mL, mix, and allow to stand for 4 hours or overnight. Filter, and to 50 mL of the clear filtrate in a platinum dish add 0.5 mL of sulfuric acid, and evaporate the mixture on a steam bath to a small volume. Carefully heat over a free flame to dryness, and continue heating to complete decomposition and volatilization of ammonium salts. Finally ignite the residue to constant weight. The weight of the residue does not exceed 5 mg (1.0%). Heavy metals— the limit is 0.002%. Organic volatile impurities— meets the requirements.

Calcium Carbonate BP Specifications
CaCO3 -- 100