Ion Association of Some 2 : 2 Electrolytes in Water at 25 °C. II. Spectrophotometric Studies of the Ion Association of Magnesium, Calcium, Manganese, Copper, and Zinc Sulfates

Abstract

Abstract Simple and mixed aqueous solutions of copper, magnesium, calcium, manganese, and zinc sulfates were spectrophotometrically studied in order to obtain the ion-association constants of the divalent metal ions with the sulfate ion. The ion-association constant of copper sulfate was obtained from the measured absorbances of copper sulfate solutions at 250 nm as a function of the closest distance of approach of ions. For the other metal sulfates which show a negligible absorption at 250 nm, absorbances were measured on the mixed solutions with copper sulfate, and the results were analyzed by the use of the results on copper sulfate in order to obtain the ion-association constants. The best values of the ion-association constant and the closest distance of approach were determined for each metal sulfate with the help of the theory of ion association. The results were compared with those obtained from the measurements of osmotic coefficients and electric conductivities. The numerical results are summarized in Table 6 of the text.