New compounds of aspartic acid Cs(ASP) . nH(2)O (n = 0, 1) have been synthesized and characterized by XRD, IR and Raman spectroscopy as well as TG. The structural formula of this new compound was Cs(ASP) . nH(2)O (n = 0, 1). The enthalpy of solution of Cs(ASP) . nH(2)O (n = 0, 1) in water were determined. With the incorporation of the standard molar enthalpies of formation of CsOH(aq) and ASP(s), the standard molar enthalpy of formation of -(1202.9 +/- 0.2) kJ.mol(-1) of Cs(ASP) and -(1490.7 +/- 0.2) kJ.mol(-1) of Cs(ASP).H2O were obtained. (C) 2004 Elsevier Ltd. All rights reserved.