Potentiometric and conductometric studies
of the nickel-thiomalic acid system, in aqueous
medium of 0. lM KNO3, reveal the formation
of two complexes; one light violet 1 : 1 predominating at pH 6.5-7.5 and
another deep violet 1 : 2 in the pH range 8.5-10.0. The stability constants of
the complexes formed have been determined by applying Calvin and Melchior's extension of Bjerrum's
method at three different temperatures and were further refined by using
alternative methods. The logK values (final) for 1 :
1 and 1 : 2 complexes at 20, 25, and 30� have been found to be 7.86, 7.87,
7.96, and 6.24, 6.31, 6.39 respectively. The values of the overall changes in ΔG,
ΔH, and ΔS accompanying the reaction have also been evaluated at 25�
and found to be -19.31 kcal/mole, -8.77 kcal/mole, and +35.36 cal/deg
respectively.