(se lee' nee us as' id).
Selenium dioxide, monohydrated;
Selenious acid [7783-00-8].
Selenious Acid contains NLT 93.0% and NMT 101.0% of H2SeO3.
Sample: 50 mg
Analysis: Dissolve the Sample in 5 mL of water. Add 100 mg of sodium bicarbonate, and mix.
Acceptance criteria: Gas bubbles develop.
Sample: 50 mg
Analysis: Dissolve the Sample in 5 mL of 0.1 N hydrochloric acid. Add 50 mg of stannous chloride.
Acceptance criteria: A curdy tan-orange precipitate is formed.
Sample solution: Transfer 100 mg to a suitable glass-stoppered flask, and dissolve in 50 mL of water.
Analysis: Add 10 mL of a 300-mg/mL potassium iodide solution and 5 mL of hydrochloric acid to the Sample solution, and mix. Insert the stopper in the flask, and allow to stand for 10 min. Add 50 mL of water and 3 mL of starch TS. Titrate with 0.1 N sodium thiosulfate VS until the solution is colorless, then titrate with 0.1 N iodine VS to a blue endpoint. Subtract the volume of 0.1 N iodine from the volume of 0.1 N sodium thiosulfate to obtain the volume of 0.1 N sodium thiosulfate equivalent to selenious acid. Each mL of 0.1 N sodium thiosulfate is equivalent to 3.225 mg of H2SeO3.
Acceptance criteria: 93.0%101.0%
• Residue on Ignition 281
Sample: 10 g
Acceptance criteria: NMT 1.0 mg (0.01%)
• Insoluble Matter
Sample: 1 g
Analysis: Dissolve the Sample in 5 mL of water.
Acceptance criteria: It dissolves completely, and the solution is clear.
• Selenate and Sulfate
Sample solution: Dissolve 0.5 g in 10 mL of water.
Analysis: Add 0.1 mL of hydrochloric acid and 1 mL of barium chloride TS to the Sample solution, and mix.
Acceptance criteria: No turbidity or precipitate is formed in 10 min.
• Packaging and Storage: Preserve in tight containers.
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USP35NF30 Page 4623Pharmacopeial Forum: Volume No. 29(5) Page 1571