Packaging and storage—
Preserve in tight containers.
Loss on drying 
731
—
Dry it over silica gel for 18 hours: it loses not more than 1.0% of its weight.
Organic volatile impurities, Method V 467:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Isomer content—
Dissolve about 300 ± 5 mg in 5 mL of sodium hydroxide solution (1 in 100), add a solution of 300 ± 5 mg of
p-nitrobenzyl bromide in 10 mL of alcohol, reflux for 30 minutes, cool, collect the precipitate on a small filter, and wash with water: the precipitate, recrystallized from 25 mL of alcohol and dried at 105
for 30 minutes, melts between 156
and 161
.
Assay—
Add about 450 mg of Secobarbital, accurately weighed, to 60 mL of dimethylformamide in a 125-mL conical flask. Add 4 drops of
thymol blue TS, and titrate with 0.1 N sodium methoxide VS, using a magnetic stirrer and taking precautions against the absorption of atmospheric carbon dioxide. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium methoxide is equivalent to 23.83 mg of C
12H
18N
2O
3.
;)
