Octadecanoic acid, calcium salt.
Calcium stearate [1592-23-0].

Packaging and storage— Preserve in well-closed containers.

Identification—

Loss on drying 731— Dry it at 105 to constant weight, using 2-hour increments of heating: it loses not more than 4.0% of its weight.

Heavy metals 231— Place 2.5 g in a porcelain dish, place a 500-mg portion in a second dish to provide the control, and to each add 5 mL of a 1 in 4 solution of magnesium nitrate in alcohol. Cover the dishes with 7.5-cm short-stem funnels so that the stems are straight up. Heat on a hot plate at low heat for 30 minutes, then heat at medium heat for 30 minutes, and cool. Remove the funnels, add 2 mL of Standard Lead Solution (20 µg of Pb) to the control, and heat each dish over a suitable burner until most of the carbon is burned off. Cool, add 10 mL of nitric acid, and transfer the solutions into 250-mL beakers. Add 5 mL of 70% perchloric acid, cautiously evaporate to dryness, add 2 mL of hydrochloric acid to the residues, and wash down the insides of the beakers with water. Evaporate carefully to dryness again, swirling near the dry point to avoid spattering. Repeat the hydrochloric acid treatment, then cool, and dissolve the residues in about 10 mL of water. To each solution add 1 drop of phenolphthalein TS and add sodium hydroxide TS until the solutions just turn pink, then add 3 N hydrochloric acid until the solutions become colorless. Add 1 mL of 1 N acetic acid and a small amount of charcoal to each solution, and filter through filter paper into 50-mL color-comparison tubes. Wash with water, dilute with water to 40 mL, add 1.2 mL of thioacetamide-glycerin base TS and 2 mL of pH 3.5 Acetate Buffer to each tube, and allow to stand for 5 minutes: the color of the test solution does not exceed that of the control. The limit is 10 µg per g.

Organic volatile impurities, Method IV 467: meets the requirements.

Residual solvents 467: meets the requirements.

Assay— Boil about 1.2 g of Calcium Stearate, accurately weighed, with 50 mL of 1 N sulfuric acid for about 3 hours using a watch glass cover to avoid splattering, or until the separated fatty acid layer is clear, adding water, if necessary, to maintain the original volume. [NOTE—Stirring may be helpful in obtaining a clear layer and decreasing extraction time.] Cool, filter, and wash the filter and the flask thoroughly with water until the last washing is not acid to litmus. Neutralize the filtrate with 1 N sodium hydroxide to litmus. While stirring, preferably with a magnetic stirrer, titrate with 0.05 M edetate disodium VS as follows. Add about 30 mL from a 50-mL buret, then add 15 mL of 1 N sodium hydroxide and 300 mg of hydroxy naphthol blue, and continue the titration to a blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 2.804 mg of CaO.

Expert Committee : (EM105) Excipient Monographs 1

USP29–NF24 Page 3289

Phone Number : 1-301-816-8262