EQUILIBRIA AMONG CONDENSED PHASES AND A MULTICOMPONENT SOLUTION USINGTHE CONCEPT OF GENERALIZED SPECIES .1. SYSTEMS WITH MIXED COMPLEXES

A method for the construction of predominance-existence diagrams (PED) in saturated multi-component solutions is discussed. The utilization of generalized species and equilibria, both in the solution and in the condensed phases, allows for the analysis of the saturation condition s from an intrinsic solubility generalized equilibrium [M(c)(tau) half arrow right over half arrow left M(tau)]. Likewise, an algorithm is p roposed for the selection of the most insoluble condensed phase M(c)(t au), from a condensed-phases diagram (CPD) dependent upon the paramete rs of the saturated solution. The CPD is constructed utilizing general ized phase interconversion equilibria, where the multi-conditional con stants are dependent only on the buffering conditions; it is also nece ssary to consider the maximum number of phases that can coexist in the system (phase rule), the electroneutrality conditions for the condens ed phases and the number of variables involved in the solubility equat ions, The consideration of mixed complexes in all phases with the prop osed algorithm is simple as it is an extension of the concept of gener alized species used previously. In order to exemplify the proposed met hod, graphical representations of the following systems are discussed: Zn(II)-H2O-H, Zn(II)-H2C2O4-H2O-H and Ca(II)-H2C2O4-H2SO4-H2O-H, wher e H2C2O4 is oxalic acid.