Abstract
Measurements of the solubility of calcium, iodate hexahydrate in some phosphate and citrate buffers are reported. Colorimetric determinations of the pH values of these various buffers, before and after saturating them with calcium iodate, are also reported. The results obtained are interpreted in terms of ion pair formation between calcium ions and phosphate ions or citrate ions. Using C. W. Davies' empirical equation relating the activity of an ion to the ionic strength of the solution, instability constants for the species CaH[2]PO[+][4], CaHPO[4], CaHCit and CaH[2]Cit[+], (Cit = citrate), are calculated by methods of successive approximations. The instability constants of the citrate complexes are discussed in relation to the work of E. Heinz. Measurements of the solubility of calcium iodate hexahydrate in various solutions of (a) calcium hydroxide, (b) calcium hydroxide and glycerol and (c) calcium hydroxide and sucrose are also reported. The results are compared and quantitative treatment is given to establish instability constants for the ion pairs CaCH[+] and CaG[+], (G- glycerol).