The measurement of hydration heats for magnesium chloride with low water by means of DSC

The heats of hydration reactions for MgCl2. 4H(2)O and MgCl2. 2H(2)O includ e two parts, reaction enthalpy and adsorption heat of aqueous vapor on the surfaces of magnesium chloride hydrates. The hydration heat for the reactio ns MgCl2. 4H(2)O+2H(2)O --> MgCl2. 6H(2)O and MgCl2. 2H(2)O+2H(2)O --> MgCl 2. 4H(2)O, measured by DSC-111, is -30.36 and -133.94 kJ mol(-1), respectiv ely. The adsorption heat of these hydration processes, measured by head-on chromatography method, is -13.06 and -16.11 kJ mol(-1), respectively. The m olar enthalpy change for the above two reactions is -16.64 and -118.09 kJ m ol(-1), respectively. The comparison between the experimental data and the theoretical values for these hydration processes indicates that the results obtained in this study are quite reliable.