This study examines the global thermal effect of the precipitation-dissolution processes of poorly soluble salts of different nature and composition under the running of arbitrary secondary reactions between the ions precipitate and saturated solution components. As secondary reactions the ligand protonation, metal ion hydrolysis, formation of neutral, protonated and hydroxocomplexes are taken into account. It has been shown that different thermodynamic functions of the summary process under real conditions are expressed differently through standard thermodynamic functions [1-2]. The potential chemical processes for the most general case of global chemical processes in the system “MA(S) - saturated aqueous solution - complexing agent” can be described by the generalized equation (1): The obtained derivatives in the expressions of thermodynamic functions may serve as differential criteria in experimental determination of the composition of polynuclear complexes in solution. The thermodynamic functions depend on the metal ion concentration [M], which can be determined from the mass balance equation:  Here CM is the total metal ion concentration. Secondly, the functional dependence of the enthalpy is proving to be fundamentally different. This fact is due to the appearance in the expression for enthalpy of the concentration functions (2) - (4). These functions are designed to the normative multipliers, taking into account the fact that the global enthalpy is to be reported to one mol of the metal ion. Within the developed approach, the global enthalpy for heterogeneous systems „ZnS(S) – aqueous solution” and „ZnS(S) – ethylene diamine – aqueous solution” has been investigated.