The mixed complex of Nd3+ with glycine and alanine, Nd(Gly)(2)(Ala)(3)Cl-3.2H(2)O, was synthesized and characterized by IR, elementary analysis, thermogravimatric analysis and chemical analysis, and the dissolution enthalpies of NdCl3.6H(2)O(s), 2Gly(s) + 3Ala(s) and Nd(Gly)(2)(Ala)(3)Cl-3.2H(2)O(S) were determined in 2 mol/L HCl by the classical solution calorimetry. By designing a thermochemical cycle according to Hess' law and through calculation, we obtained the reaction enthalpy of neodymium chloride six-hydrate with glycine and alanine: Delta(r)H(m)(o) (298.15 K) = 37.24 +/- 0.299 kJ/mol, and the standard enthalpy of formation of Nd(GlY)(2)(Ala)(3)Cl-3.2H(2)O(s): A(f)H(m)(o)[Nd(Gly)(2)(Ala)(3)Cl-3.2H(2)O, s, 298.15 K] = -4441.6 +/-8.262 kJ/mol. (C) 2004 Published by Elsevier B.V.