Solubility product of the cadmium phosphate Cd5H2(PO4)(4)center dot 4H(2)Oat 37 degrees C

The solubility product of Cd5H2(PO4)(4). 4H(2)O at 37 degreesC has been det ermined by mixing dilute solutions of cadmium nitrate and ammonium phosphat e and measuring cadmium and phosphate concentrations as well as the pH valu es of the saturated solutions. Using the definition K-sp = a(Cd2+)(5)a(HPO4 2-)(4)/a(H+)(2), the value pK(sp) = (30.9 +/- 0.3) was found. Necessary val ues of stability constants of cadmium phosphate complexes in solution were estimated from literature values determined at high ionic strength with the aid of mean ion activity coefficients from independent sources.