Elemental analysis for the synthesized crystalline lamellar compound conforms to the formula Ba(H2PO4)(2) and the X-ray diffraction patterns is in agreement with the lamellar structure for this compound. The precursor host was intercalated with a series of n-alkylmonoamines of the general formula H3C(CH2)(n)-NH2 (n = 1 to 4) in aqueous solution. The lamellar host was calorimetrically titrated with an aqueous amine solution at T = (298.15 +/- 0.02) K and the enthalpy, Gibbs free energy and entropy were calculated. The enthalpic values increased, although not uniformly, with the number of carbon atoms is the amine chain, to give (- 13.96 +/- 0.12, - 14.00 +/- 0.48, -15.75 +/- 0.23, -16.05 +/-0.11) kJ . mol(-1), from n = 1 to 4. The exothermic enthalpy, the negative Gibbs free energy and positive entropic values are in agreement with the favourable energetic process of intercalation for this system. (C) 2005 Elsevier Ltd. All rights reserved.