Interactions occurring between mercapto-modified silica gel and silver, mercury, copper and zinc ions in ethanolic solutions have been investigated by using calorimetric titrations with direct determination of the reaction extension. A calorimetric technique is described for the simultaneous determination of thermal effects acid quantities of cations that interact at each titration point. From this procedure, values of maximum capacity of interaction (N-s), differential interaction enthalpies at different coverages of the surface (Delta(int(i))H-m), integral energy of interaction (Q(mon)) and molar integral enthalpy of interaction for a monolayer (Delta(mon)H(m)) have been obtained. The maximum capacity of interaction values are compared with those previously published for analogous interaction processes in aqueous solutions. Thermochemical quantities are discussed in terms of evaluation criterion of the acid-base interactions, and generally support the conclusion that the Pearson's hypothesis of hard and soft acids and bases is appropriated to describe the behavior of the interaction of the above-mentioned cations.