Nickel complexes of Thioglycolic acid have been investigated by potentiometric technique in 40% V/V acetone. It was found that nickel forms colourless 1:2 complexes. The stability constant of the compexes formed have been determined by applying Calvin and Melchior’s extension of Bjerrum’s method at three different temperature. The values of log K₁, log K₂ at 25º C, 30º C and 35º C have been found to be 8.08, 6.55, at 298 K, 8.28, 6.64 at 303 K, and 8.57, 6.87 at 308 K, in 40% acetone medium respectively. The values of overall changes in DG, DH and DS, at three different temperature accompanying the reaction have also been evaluated at 303 K and the values of DG₁, DG₂, DH, DS₁, DS₂ are found to be –48.03 KJ mol-1 –38.52 KJ mol^–1 and –0.14360 KJ mol^–1 +158.040 J/K, +126.654 J/K in 40% acetone medium.