CALCULATION OF THE GIBBS ENERGY OF MIXING IN CRYSTALS USING PITZERS MODEL

Pitzer's model has been applied to the thermodynamic study at 25-degre es-C of a series of systems of the type MeX-Me'X-H2O, MeX-MeX'-H2O (wh ere Me, Me' = K, NH4,Rb and Cs; X, X' = Cl, Br and I), MeSO4-Me'SO4-H2 O (where Me, Me' = Mg, Ni, Zn and Co). The integral Gibbs energy of mi xing G(mix) and the excess Gibbs energy of mixing G(E)(s) are calculat ed, and simplified correlation equations are proposed for their calcul ation. The results obtained are compared with experimental data from t he literature and with values calculated using various theories. The r ational activity coefficients of the mixed crystal components are esti mated. The energy of phase transition of one structure into another ha s been estimated for the isodimorphous mixed crystals in the system Mg SO4-CoSO4-H2O.