Studies have been made on the association in aqueous solution between divalent transition metal ions and the anions of mono-and di-carboxylic acids. The thesis is divided into four parts. In Part I the association between the nickel ion and the malonate and n-butylmalonate anions has been studied using a cell incorporating a pair of glass electrodes and a pair of silver, silver chloride electrodes. In order to determine the best activity coefficient expression to be used, both systems were studied at low concentration, activity coefficients being calculated from the Davies equation, and at constant ionic strengths of 0.03, 0.05, 0.10, 0.15 and 0.20 M. The stability constants have been extrapolated to zero ionic strength and the thermodynamic constants are compared with those determined at low concentration. Part II deals with the study of the association of the divalent nickel, cobalt and manganese ions with the glycinate and beta-alaninate anions over the temperature range of 0° to 45°C using the cell Hg/Pt/HA, NaOH, MCl2,/AgCl/Ag. Activity coefficients were calculated from the equation for various values of beta. A comparison of the results shows that for low ionic strengths consistent association constants are obtained with 0 ≤ beta ≤ 1. The constants determined with beta = 0.2 have been used in the calculation of the thermodynamic properties. The dissociations of beta-alanine have been measured over the same temperature range and the results are compared with those in the literature. Part III describes a calorimetric determination of the heats of formation of the complexes studied in Part II. The heat of solution of potassium chloride has also been determined in order to calibrate the calorimeter. Part IV consists of a general discussion of the results. The heat and entropy data are discussed in relation to ionic sizes and electronic structure and the entropies of ion-pairs have been calculated
