ตำรายาของประเทศไทย
Thai Pharmacopoeia
สำนักยาและวัตถุเสพติด กรมวิทยาศาสตร์การแพทย์ กระทรวงสาธารณสุข
Bureau of Drug and Narcotic, Department of Medical Sciences, Ministry of Public Health5.12 PEROXIDE VALUE
The peroxide value is the number of milliequivalents of active oxygen that expresses the amount of peroxide contained in 1000 g of the substance, when determined by the following method.
Procedure
Place about 5 g of the test substance, accurately weighed, in a 250-ml glass-stoppered conical flask. Add 30 ml of a mixture of 30 volumes of glacial acetic acid and 20 volumes of chloroform, shake until dissolved and add 0.5 ml of a saturated solution of potassium iodide. Shake for exactly 1 minute, add 30 ml of water and titrate slowly, shaking continuously, with 0.01 M sodium thiosulfate VS until the yellow colour almost disappears. Add 5 ml of starch TS and continue the titration, shaking vigorously, until the blue colour just disappears. Repeat the operation without the test substance.
Calculate the peroxide value from the expression:
where V = difference, in ml, between the titrations,
M = molarity of 0.01 M sodium thiosulfate VS, and
W = weight, in g, of the test substance.
The volume of 0.01 M sodium thiosulfate VS used in the blank determination must not exceed 0.1 ml.