Ethylenediamine dihydrochloride (C2H10N2Cl2)(s) was synthesized. The crystal structure of the compound has been determined by X-ray crystallography. The lattice potential energy and ionic radius of the cation of the Compound were obtained from the crystallographic data. Molar enthalpies of dissolution of the compound in double-distilled water under various values of molality were determined at T = 298.15 K by an isoperibol solution-reaction calorimeter Following to Pitzer's theory, the molar enthalpy of dissolution of the compound at infinite dilution (Delta H-sol(m)infinity) and the Pitzer parameters (beta((O)L)(MX) and beta((I)L)(MX)) were obtained. The values of relative apparent molar enthalpies (Phi(L)), relative partial molar enthalpies ((L) over bar (2)) of the compound and relative partial molar enthalpies ((L) over bar (1)) of the solvent at different concentrations m/(mol . kg(-1)) were derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the hydration enthalpy of the cation of the Substance was calculated by designing a thermochemical cycle. (C) 2009 Elsevier Ltd. All rights reserved.