Abstract
The enthalpy changes involved in the complex formation of Cu(II), Ni(II), Co(II), Zn(II), Cd(II) with several 2‐substituted pyridine derivatives have been determined by direct calorimetric measurements at 25°C, in 0,5 M KNO3 solution. From these and the stability constants of the complexes, δS has been calculated. Changes in δH and δS are discussed in terms of hydrational, inductive and steric effects.