A physico-chemical and electrochemical study of aqueous barbituric acid and sodium barbital at 25c

Abstract

Derivatives of Barbituric Acid like Barbitone, Phenobarbitone, Soneryl, Numbutal and Amytal etc. have long been used as a powerful hypnotic and soporitic medicine for the treatment of epilepsy and other ailments which warrant sedation. In spite of age-long use of these compounds, it was surprising to note that physico-chemical data on these chemicals are rather meagre in the literature. It thus became the objective of the present project to produce precise physicochemical data of such pyrimidines so as to have a better understanding of the mode of physiological action of these medicinal compounds. Accordingly density, viscosity, refractive index, conductance and diffusion coefficient measurements were undertaken in aqueous Barbituric Acid and Sodium Barbital solutions at 25°C. The investigation has produced equations which describe the concentration dependence of density, refractive index and relative viscosity in a wide range of concentration. Partial molal volume V, for Barbituric Acid and Sodium Barbital 3 , -1 have been found to be 74.3 and 125.2 cm mol respectively. An important observation in this connection is that Sodium Barbital produces a decrease in effective volume. Conductance measurements have yielded A0 = 372.31 + 0.5 Scm2equiv._1 and K = (1.01+.01) x 10~4 “ a “ mol 1. for Babituric Acid> and A0 = 89.91 + 0.05 2 ”1 and = 39.00 + 0.5 Scm equiv. as limiting conductance values for the salt and diethyl-Barbiturate ion. Likewise the diffusion studies have given D° - 5 2 -1 = (1.196 +.02) x 10 cm Sec for the undissociated r o i acid and D° = (0.599 + .02) 10 cm sec . for an isolated ion. The diffusion coefficient of the salt has been found to be (1.181 + 0.02)10 ^ cm2 sec. ^. All these result^ indicate a strong ion-ion and ion-solvent interactions.