A non-aqueous method for assay of barbituric acid and some of its commercial preparations

Abstract

A rapid and accurate method for visual non-aqueous titration of barbituric acid has been presented.The recommended procedures are as follows.Pure barbituric acid: 350450 mg of the acid is dissolved in 50 ml of chloroform-ethanol (10:1) or dimethylformamide by stirring with 1 ml of 0.1% Alizarine Yellow GG-0.1% Thymolphthalein mixture (1:2), and titrated to violet or green blue end point with 0.1N potassium hydroxide in ethanol.Sodium barbiturate and its tablets: 500mg of sample dissolved in 15 ml of water is taken in a separatory funnel with 10 ml of 10% hydrochloric acid. The liberated barbituric acid is extracted into chloroform.The extract (150 ml in volume) washed with water is filtered and, after the addition of 10 ml of ethanol and 2 ml of 0.1% Alizarine Yellow GG-0.1% Thymolphthalein mixture(1:2), is titrated with 0.1N potassium hydroxide in ethanol as above.Barbituric acid tablets: Twenty tablets are powdered and 1 g is taken in a 100 ml volumetric flask. Seventy milliliter of chloroform-ethanol (10:1) is added, shaken for 15 min., and after 30 min. made up to 100 ml with the chloroform-ethanol. It is then filtered throuth a glass filter, and its 50 ml aliquot is titrated as above.