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

Identification— A1in 10suspension is colored purplish blue to deep blue by iodine TS.

Stability to autoclaving— Transfer about 2g 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 121for 30minutes,and cool:the powder is not caked,and any lumps are easily crushed between the fingers.

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

pHá791ñ: between 10.0and 10.8,in a 1in 10suspension.

Loss on drying á731ñ— Dry about 2g,accurately weighed,at 105to constant weight:it loses not more than 12%of its weight.

Residue on ignition á281ñ— Heat about 1g,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 IIá231ñ: 0.001%.

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

Expert Committee:(GTB)General Toxicology and Biocompatibility

USP28–NF23Page 705

Phone Number:1-301-816-8339