» Thymol contains not less than 99.0 percent and not more than 101.0 percent of C10H14O.
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
B: It meets the requirements under Melting range.
Melting range 741: between 48 and 51; but when melted, Thymol remains liquid at a considerably lower temperature.
Limit of nonvolatile residue Volatilize about 2 g, accurately weighed, on a steam bath, and dry at 105 to constant weight: not more than 0.05% of residue remains.
Assay Transfer about 100 mg of Thymol, accurately weighed, to a 250-mL iodine flask, and dissolve in 25 mL of 1 N sodium hydroxide. Add 20 mL of hot dilute hydrochloric acid (1 in 2), and immediately titrate with 0.1 N bromine VS to within 1 to 2 mL of the calculated endpoint. Warm the solution to between 70 and 80, add 2 drops of methyl orange TS, and continue the titration slowly, swirling vigorously after each addition. When the color of the methyl orange is bleached, add 2 drops of 0.1 N bromine VS, shake for 10 seconds, add 1 drop of methyl orange TS, and shake vigorously. If the solution is red, continue the titration, dropwise and with shaking, until the color is discharged. Repeat the alternate addition of the titrant and the methyl orange TS until the red color is discharged after the addition of the TS. Each mL of 0.1 N bromine is equivalent to 3.755 mg of C10H14O.
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USP35NF30 Page 2005Pharmacopeial Forum: Volume No. 31(3) Page 821