D. MONOGRAPHS

Calcium Carbonate CaCO3 Mol. Wt. 100.09 〔471-34-1〕 Content Calcium Carbonate, when dried, contains 98.0－102.0% of calcium carbonate (CaCO3). Description Calcium Carbonate occurs as a fine white powder. It is odorless. Identification To 1 g of Calcium Carbonate, add 10 ml of water and 7 ml of diluted acetic acid (1→ 4). It effervesces and dissolves. This solution, after being boiled and neutralized with ammonia TS, responds to all tests for Calcium Salt as described in the Qualitative Tests. Purity (1) Hydrochloric acid-insoluble substances Not more than 0.20%. Weigh 5.0 g of Calcium Carbonate, add 10 ml of water, and add dropwise gradually 12 ml of hydrochloric acid while stirring, and add water to make 200 ml. Filter through a filter paper for quantitative analysis (5C), wash thoroughly the residue on the filter paper with boiling water until the washings do not respond to the test for Chloride, incinerate together with the filter paper, and weigh the residue. (2) Free alkali Weigh 3.0 g of Calcium Carbonate, add 30 ml of freshly boiled and cooled water, shake for 3 minutes, and filter the solution. Measure 20 ml of the filtrate, and add 2 drops of phenolphthalein TS. Even if a pink color develops, it disappears when 0.20 ml of 0.1 mol/l hydrochloric acid is added. (3) Heavy metals Not more than 20 µg/g as Pb. Test Solution Weigh 1.0 g of Calcium Carbonate, dissolve in 8 ml of diluted hydrochloric acid (1 → 4), add water to make about 20 ml, and add dropwise ammonia TS while shaking until slight white turbidity appears. Add 2 ml of diluted acetic acid (1 → 20) and water to make 50 ml. Control Solution To 2 ml of Lead Standard Solution, exactly measured, add 2 ml of diluted acetic acid (1 → 20) and water to make 50 ml. (4) Alkali metals and magnesium Not more than 1.0%. Weigh 1.0 g of Calcium Carbonate, dissolve by gradually adding 30 ml of diluted hydrochloric acid (1 → 10), expel carbon dioxide while boiling. Cool, neutralize with ammonia TS, add 60 ml of ammonium oxalate solution (1 → 25), and heat on a water bath for 1 hour. After cooling, add water to make 100 ml, stir thoroughly, and filter. Measure 50 ml of the filtrate, add 0.5 ml of sulfuric acid, evaporate to dryness, and ignite to constant weight, and weigh the residue. (5) Barium Not more than 0.030% as Ba. Test Solution Weigh 1.0 g of Calcium Carbonate, dissolve in 8 ml of diluted hydrochloric acid (1 → 4), add water to make 20 ml.

D. MONOGRAPHS

Control Solution To 0.30 ml of Barium Standard Solution, add water to make 20 ml. Procedure Add 2 g of sodium acetate, 1 ml of diluted acetic acid (1 → 20), and 0.5 ml of potassium chromate solution (1 → 20) to the test solution, and allow to stand for 15 minutes. The solution is not more turbid than the control solution. (6) Arsenic Not more than 4.0 µg/g as As2O3. Test Solution Weigh 0.50 g of Calcium Carbonate, moisten with 1 ml of water, and dissolve in 4 ml of hydrochloric acid (1 → 4). Apparatus Apparatus B. Loss on Drying Not more than 2.0% (200℃, 4 hours). Assay Weigh accurately about 1 g of Calcium Carbonate, previously dried, gradually dissolve in 10 ml of diluted hydrochloric acid (1 → 4), gradually added, add water to make exactly 100 ml, and use this solution as the test solution. Proceed as directed under Method 1 in Calcium Salt Determination. 1 ml of 0.05 mol/l EDTA = 5.004 mg of CaCO3