Spectrophotometric Investigation on the Kinetics of Decomposition of Murexide in Acid Solutions

Abstract

The kinetics of the decomposition of murexide in acid solutions were investigated spectrophotometrically by following the absorption at λ=530 mμ. The optical density of murexide at λ= 530 mμ which obeyed Beer's law, decreased irreversibly with time, following a first order law. The corresponding rate constant k, was dependent upon the concentration (C) of the strong acids like HCl, HBr, HNO3, etc. and followed a relationship: k/min-1 = 2.56·10-3·C. k was also dependent upon the concentration of murexide. The effect of neutral salts on k showed that in accord with the data obtained with different acids, the anions of the acids or salts had no significant role in the mechanism responsible for the decomposition of murexide. A hypothesis referring to the formation of an intermediate complex (electrically uncharged in character) which decomposed unimolecularly to give the products, uramil and alloxan, was put forward.