Packaging and storage—
Preserve in well-closed, light-resistant containers.
Identification—
B:
Mercuric chloride TS produces in a solution (1 in 200) a white precipitate, but no precipitation is produced by trinitrophenol TS. The solution is colored intensely blue by molybdophosphotungstate TS.
Ordinary impurities 
466
—
Test solution:
ethyl acetate.
Standard solution:
ethyl acetate.
Eluant:
a mixture of toluene, isopropyl alcohol, and ammonium hydroxide (70:29:1), in a nonequilibrated chamber.
Visualization:
2.
Organic volatile impurities, Method I 467:
meets the requirements.
Assay—
Dissolve about 250 mg of Methimazole, accurately weighed, in 75 mL of water. Add from a buret 15 mL of 0.1 N sodium hydroxide VS, mix, and add, with agitation, about 30 mL of 0.1 N silver nitrate. Add 1 mL of
bromothymol blue TS, and continue the titration with the 0.1 N sodium hydroxide VS until a permanent, blue-green color is produced. Each mL of 0.1 N sodium hydroxide is equivalent to 11.42 mg of C
4H
6N
2S.
;)
for 2 hours: it loses not more than 0.5% of its weight.