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The dissociation constants of amino acids are generally determined by acid-base titration and by the emf method. The use of the conductimetric method to obtain pK for amino acids appears to be the first of its kind. In this study, we describe the method of measurement, the treatment of the data and discuss the results. The choice of MOPSO for the investigation is in conjunction with the development of new buffer systems as pH Standard Reference Materials. The value for pK at 25°C is 0.060±0.005.

The themodynamic properties of solutions of deuterium chloride (DCl) in deuterium oxide (D2O) have been determined from emf measurements of the electrochemical cell without transference from 5 to 50°C, and from 0.002 to 1.0 mol-kg-1. The standard potential of the silver/silver chloride electrode relative to the platinum/deuterium electrode has been determined. An equation for the Gibbs energy as a function of temperature has been derived from which the enthalpy, entropy, and heat capacity have been computed. Equations for the activity coefficient and the osmotic coefficient of DCl in D2O have been developed. The excess Gibbs energy of the solution and the excess partial molar free energy as a function of temperature have been calculated, from which the other excess thermodynamic properties have been computed. The values for the heat capacity and the apparent molar heat capacity have been compared with calorimetric data in the literature. The relative partial molar enthalpy has been calculated. The solvent isotope effect on the excess thermodynamic functions is discussed.