Ion Association of Some 2 : 2 Electrolytes in Water at 25 °C. I. Studies of Magnesium, Calcium, Manganese, and Tris(1,10-phenanthroline)-ruthenium(II) Sulfate Solutions with a Vapor-Pressure Osmometer

Abstract

Abstract The osmotic coefficients of aqueous solutions of magnesium, calcium, manganese, and tris(1,10-phenanthroline)ruthenium(II) sulfates were measured at 25 °C by means of a vapor-pressure osmometer. Then the ionassociation constants of these electrolytes were obtained as a function of the closest distance of approach of ions from the measured osmotic coefficients as well as from the available conductivity and cryoscopy data. The best values of the closest distance of approach and the ion-association constant (given in Table 6) were estimated with the help of theories of ion association. The formation of triple-ions and quadrupoles and the hydration of ions are also discussed in connection with the ion-association constant.