Packaging and storage— Preserve in well-closed containers. It may be preserved in sealed paper packets.

Identification— A 1 in 10 suspension is colored purplish blue to deep blue by iodine TS.

Stability to autoclaving— Transfer about 2 g to a suitable paper packet, and seal or close the packet with a double fold. Wrap the paper packet in muslin, transfer to an autoclave, heat to 121 for 30 minutes, and cool: the powder is not caked, and any lumps are easily crushed between the fingers.

Sedimentation— Boil 100 mL of a 1 in 10 suspension in water for 20 minutes. Cool, transfer to a 100-mL graduated cylinder, dilute with water to volume, and allow to stand undisturbed for 24 hours: the volume occupied by the settled Powder is between 45 mL and 75 mL.

pH 791: between 10.0 and 10.8, in a 1 in 10 suspension.

Loss on drying 731— Dry about 2 g, accurately weighed, at 105 to constant weight: it loses not more than 12% of its weight.

Residue on ignition 281— Heat about 1 g, accurately weighed, in a covered platinum crucible until most of the carbon is burned away, but do not ignite the sample. Remove the cover, and ignite to constant weight: not more than 3.0% of residue remains.

Heavy metals, Method II 231: 0.001%.

Assay for magnesium oxide— Weigh accurately about 2.5 g, and transfer to a beaker. Add 25 mL of water and 2 mL of 3 N hydrochloric acid, and stir the mixture for 5 minutes. Add 5 mL of hydroxylamine hydrochloride solution (1 in 10), 15 mL of ammonia-ammonium chloride TS, 5 mL of potassium cyanide solution (1 in 10), and 5 drops of eriochrome black TS, mix, and titrate with 0.05 M edetate disodium VS until the solution becomes distinctly blue in color. Each mL of 0.05 M edetate disodium is equivalent to 2.015 mg of MgO.

Topic/Question	Contact	Expert Committee
Monograph	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(GTMDB05) General Toxicology and Medical Device Biocompatibility

USP32–NF27 Page 2221