Packaging and storage— Preserve in tight containers.

Labeling— Label it to indicate the maximum percentage of Loss on drying.

pH 791: between 4.0 and 8.5 in a slurry (1 in 20).

Loss on drying 731— Dry it at 105 for 2 hours: it loses not more than the maximum percentage of its weight, as indicated in the labeling.

Sodium sulfate— Transfer about 1 g of Dental-Type Silica, accurately weighed, to a platinum dish, wet with a few drops of water, add 15 mL of perchloric acid, and place the dish on a hot plate. Add 10 mL of hydrofluoric acid. Heat until copious fumes are evolved. Add 5 mL of hydrofluoric acid, and again heat to copious fumes. Add about 5 mL of boric acid solution (1 in 25), and heat to fumes. Cool, and transfer the residue to a 400-mL beaker with the aid of 10 mL of hydrochloric acid. Adjust the volume with water to about 300 mL, and bring to boiling on a hot plate. Add 20 mL of hot barium chloride TS. Keep the beaker on the hot plate for 2 hours, maintaining the volume above 200 mL. After cooling, transfer the precipitate and solution to a dried, tared 0.8-µm porosity filter crucible. Wash the filter and precipitate 8 times with hot water, dry the crucible at 105 for 1 hour, and weigh. The weight, multiplied by 0.6085, is the Sodium sulfate content of the amount of specimen taken. Not more than 4.0% is found.

Other requirements— It meets the requirements for Loss on ignition, Chloride, Arsenic, Heavy metals, and Assay under Silicon Dioxide.

Topic/Question	Contact	Expert Committee
Monograph	Robert H. Lafaver, B.A. Scientist 1-301-816-8335	(EM105) Excipient Monographs 1

USP32–NF27 Page 1336