P. G. Department of Chemistry, G. M. College, Sambalpur-768 004 Department of Ceramic Science, State University of New York College of Ceramic at Altered University, N. Y. 14802; U.S.A. Manuscript received 15 February 1983, accepted 1 September 1983 Infrared spectra of mixed calcium-barium-cadmium hydroxylapatites were studied in the 4000-200 cm-1 range and probable band assignments are given. The introduction of Ba2+/Cd2+ in calcium hydroxylapatite results in the formation of their solid solu­tions. In the infrared spectral studies of the samples, the vibrations corresponding to v4 \(PO_4^3\)- ions and v1, and v3 of OH-1 are shifted to lower frequencies due to effect of binding energy and atomic mass as a result of substitution of Ca2+ by Ba2+/Cd2+. The crystal dimensions also increase and could be observed in the electron microscopic patterns of the samples. The solubilities of solid solutions of calcium-barium-cadmium hydroxylapatites determined in the pH range 5.0-8.0 decrease with increase in pH of the dissolving medium. This is due to dissolved phosphate ions functioning as proton acceptors. Being salts of weak acid the samples undergo hydrolysis in aqueous media. At a given pH the solubility of the samples increases with the increase of mole content of barium and cadmium in the mixed hydroxylapatites.