The stability constants of the Co(II), Ni(II), Cu(II) and Zn(II) complexes with 2-benzoylpyridine 4-phenyl-3-thiosemicarbazone were determined using a spectrophotometric method at different temperatures (25, 30, 35 and 40 \pm 0.1oC) and ionic strengths (0.05, 0.01 and 0.20 M KNO3) in 50 % (v/v) aqueous ethanol. Plots of thermodynamic stability constants at zero ionic strength (\ln Ko) versus T-1 gave linear curves and D Ho and D So were also calculated from these plots. Moreover, the changes in free energy for each metal-ligand system were calculated from the following equation. D Go = -RT \ln Ko.

The stability constants of the Co(II), Ni(II), Cu(II) and Zn(II) complexes with 2-benzoylpyridine 4-phenyl-3-thiosemicarbazone were determined using a spectrophotometric method at different temperatures (25, 30, 35 and 40 \pm 0.1oC) and ionic strengths (0.05, 0.01 and 0.20 M KNO3) in 50 % (v/v) aqueous ethanol. Plots of thermodynamic stability constants at zero ionic strength (\ln Ko) versus T-1 gave linear curves and D Ho and D So were also calculated from these plots. Moreover, the changes in free energy for each metal-ligand system were calculated from the following equation. D Go = -RT \ln Ko.