Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The equilibrium solubility of the ternary system cadmium chloride + dl-alanine (Ala) + water was determined at 298.15 K, and the corresponding equilibrium diagram was constructed. The ternary system is complicated with three equilibrium solid phases, CdCl2*2.5H2O, Cd3(Ala)2Cl6*4H2O, and Ala, of which a new compound of Cd3(Ala)2Cl6*4H2O was found to be congruently soluble in the system. The new compound obtained was identified and characterized by the methods of IR, elementary analysis, X-ray diffraction, X-ray diffraction single crystal structure analysis, thermogravimetry, and differential thermogravimetry. It belongs to the monoclinic system, with space group P2(1)/n, a = 0.70393(16) nm, b = 0.9074(2) nm, c = 1.6982(4) nm, ? = 92.529(4)deg , V = 1.0837(4) nm3, Dc = 2.434 g*cm-3, Z = 2. The dissolution enthalpies of Ala, CdCl2, and Cd3(Ala)2Cl6*4H2O in 2 mol*dm-3 H2SO4 were measured by heat conduction microcalorimetry. By designing a thermochemical cycle according to Hess Law and through calculation, we obtained the reaction enthalpy of Ala with cadmium chloride, ?rHm?(298.15 K) = -(50.86 +- 0.77) kJ*mol-1, and the standard molar enthalpy of formation of Cd3(Ala)2Cl6*4H2O, ?fHm? = -(3499.9 +- 1.1) kJ*mol-1.