(zink ox' ide).
Zinc oxide [1314-13-2].
Zinc Oxide, freshly ignited, contains NLT 99.0% and NMT 100.5% of ZnO.
• A. When strongly heated, it assumes a yellow color that disappears on cooling.
• B. Identification TestsGeneral, Zinc 191
Sample solution: Dissolve in a slight excess of 3 N hydrochloric acid.
Acceptance criteria: Meets the requirements
Sample: 1.5 g, freshly ignited
Analysis: Dissolve the Sample and 2.5 g of ammonium chloride in 50.0 mL of 1 N sulfuric acid VS, with the aid of gentle heat, if necessary. When solution is complete, add methyl orange TS. Titrate the excess sulfuric acid with 1 N sodium hydroxide VS. Each mL of 1 N sulfuric acid is equivalent to 40.69 mg of ZnO.
Acceptance criteria: 99.0%100.5% on the ignited basis
• Arsenic, Method I 211: NMT 6 ppm
Sample solution: Add 2 g to 20 mL of water, stir well, and add 5 mL of glacial acetic acid. Warm on a steam bath until dissolved.
Analysis: Add 5 drops of potassium chromate TS.
Acceptance criteria: No turbidity or precipitate is produced.
• Iron and Other Heavy Metals
Sample solution: Use the solution from Carbonate and Color of Solution.
Analysis: Cool 2 separate 5-mL aliquots of the Sample solution. Add potassium ferrocyanide TS to the first aliquot, and add sodium sulfide TS to the second aliquot.
Acceptance criteria: White precipitates are formed in both aliquots.
• Loss on Ignition 733: Ignite 2 g at 500 to constant weight: it loses NMT 1.0% of its weight.
Analysis: Mix 1.0 g with 10 mL of hot water, add 2 drops of phenolphthalein TS, and filter.
Acceptance criteria: If a red color is produced, NMT 0.30 mL of 0.10 N hydrochloric acid is required to discharge it.
• Carbonate and Color of Solution
Analysis: Mix 2.0 g with 10 mL of water, add 30 mL of 2 N sulfuric acid, and heat on a steam bath with constant stirring.
Acceptance criteria: No effervescence occurs, and the resulting solution is clear and colorless. [NoteUse this solution in the test for Iron and Other Heavy Metals. ]
• Packaging and Storage: Preserve in well-closed containers.
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USP35NF30 Page 5073Pharmacopeial Forum: Volume No. 31(1) Page 80