Barbituric acid derivatives and salts and their allied compounds used as medicinal drugs were titrated as approx. 0.1N glacial acetic acid solution (25cc.) at around 25° with 0.1N perchlorate solution, using calomel-glass electrode. The titration curves were very sharp and the precision of determination was approx. 0.05%. Titration using crystal violet, malachite green, methyl violet, or neutral red as an indicator was found to be almost as accurate as the potentiometric titration if one of the first three indicators was suitably used. This titration by the indicator is suitable as a method for Pharmacopoeia test in the face of the fact that there are no other good quantitative method. Only in the case of ethylhexabital calcium, it was found necessary to use a comparative standard for end point because of its weak basicity. It is necessary to shut off air during titration, to maintain the moisture of glacial acetic acid around 1-0.5%, to correct the concentration of 0.1N perchlorate standard with the expansion coeffcient of glacial acetic acid, and to maintain the temperature difference of the room during titration to within 0.5°. The dielectric rate of glacial acetic acid is considerably lower than that of water that the titration must be made slowly. When the sample contains some impurities such as sodium carbonate the value will be extremely larger than the actual content.