Department of Chemistry, Patna University, Patna-800 005 Manuscript received 26 December 1988, revised 10 June 1989, accepted 21 June 1989 The ioaisation constant of barbital (5,5' diethyl barbituric acid) has been determined by e m f. methods at temperatures varying from 15 to 45° in a mixed solvent consiting of 80% (w/w) ethanol+ 20% water. The values found for pK are 9.456 9.510, 9.546, 9.588, 9 623. 9.674 and 9,728, respectively at 15, 20, 25, 30, 35, 40 and 45°. Related thermodynamic

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... ons like the Gibbs free energy), entropy, enthalpy and heat capacity changes have been evaluated. Certain polynomials have been sugested for implementing Gronwall, LaMer and Sandved corrections and a computer has been used for carrying out the iterative calculations involved.