Aqueous solubility of calcium citrate tetrahydrate was found to decrease with increasing temperature, while solubility of hexahydrate increased with a transition temperature at 51.6 °C. Excess citrate increased calcium citrate solubility but decreased the calcium ion activity of the saturated solution with an initial solubility overshooting to form supersaturated solutions indicating binding of calcium to citrate with an association constant of 3.6 ± 0.1 × 10⁴, δH^o = -5.07 ± 0.04 kJ mol^-1, δS^o = 70.3 ± 0.3 J mol^-1 K^-1 at 25 °C. Dissolution of the tetrahydrate and hexahydrate was found to have δH^o = 27 ± 9 kJ mol^-1, δS^o = -218 ± 30 J mol^-1 K^-1 and δH^o = 57 ± 7 kJ mol^-1, δS^o = -126 ± 24 J mol^-1 K^-1, respectively, as determined from the temperature dependence of solubility corrected for complex formation. The exothermic complex formation results in inverse solubility only for the tetrahydrate with its moderate endothermic dissolution, which also precipitates at ambient temperature rather than the less soluble hexahydrate.