Structural effects and microheterogeneity in concentrated solutions and their role in the formation of cadmium chloride complexes

The proton relaxation rate and Raman spectra in the regions of vibrations o f the Cd-Cl, Cd-OH2 groups and bending vibrations nu (4) of nitrate ions in the systems CdAn(2)-NaCl-H2O (An = Cl-, ClO4-, NO3-) were measured. In the range of subeutectic concentrations of cadmium salts all possible forms of chloride complexes of cadmium are formed. In the posteutectic region the f ormation of complexes is structurally induced, it depends on the nature of dominating cybotactic groups and is limited to the formation of only low-co ordinate forms. The mechanisms of the formation of chloride complexes in pe rchlorate and nitrate systems were proposed. It was concluded that, in cont rast to the chloride system, the nitrate and perchlorate systems in the pre sence of sodium chloride are characterized by structural microheterogeneity . The distinctions in the nature of the microheterogeneity and its effect o n the complex formation were considered. The solubility polytherm and Raman spectra of the system Cd(NO3)(2)-NaCl-H2O with a high content of the both salts were measured. The causes of abnormally high mutual solubility of nit rate salts in multicomponent solutions containing salts that crystallize in the hydrated and anhydrous forms were suggested.