Crystal structure of n-decylammonium ethyl sulfate was determined by X-ray crystallography. Lattice potential energy and molar volume of the solid compound and its anion were respectively obtained. Ionic radius of the anion was calculated from the corresponding effective volume of the anion. Molar enthalpies of dissolution of the compound at different concentrations m /(mol . kg(-1)) were measured by an isoperibol solution-reaction calorimeter at T = 298.15 K. According to the Pitzer's electrolyte solution theory, molar enthalpy of dissolution of the compound at infinite dilution (Delta H-sol(m)infinity) was determined to be (21.284 +/- 0.042) kJ.mol(-1), and enthalpy of hydration of the anion SO4C2H5 was calculated to be Delta H- = -340.68 kJ.mol(-1). The values of apparent relative molar enthalpies (L-Phi) of the title compound and relative partial molar enthalpies ((L-2) over bar and (L-1) over bar) of the solute and the solvent at different concentrations were derived from experimental values of enthalpies of dissolution of the compound. Finally, enthalpies of hydration of the compound and its anion were calculated by designing a thermochemical cycle in accordance with lattice potential energy and molar enthalpy of dissolution at infinite dilution. (C) 2012 Elsevier Ltd. All rights reserved.