The kinetics of the formation of MnHPO4and Cd3(PO4)2in solution were studied in order to determine the overall reaction order and the rate constant at various temperatures for each reaction. Known concentrations of cation were added to a saturated solution of monopotassium phosphate (MKP) which was kept at a constant temperature. Aliquots of the reaction solution were removed at various time intervals and analyzed. The reaction temperatures ranged between 20–60°C with the reaction time varied between 3 and 12 hours. Results indicate that both MnHPO4and Cd3(PO4)2are second order overall reactions, with Mn(II), Cd(II), HPO4‐2, and PO4‐3being first order with respect to their appropriate reactions. The rate constant for each reaction was found to increase with temperature and to conform to the Arrhenius equation. The activation energy and the pre‐exponential constant for each reaction was calculated from the Arrhenius equation.