Lamellar α-titanium hydrogenphosphate (α-TiP) suspended in water or 1,2-dichloroethane (dce) intercalates ≈7.70 meq g1 of n-alkylamines (C1-C4), as determined by potentiometry and thermogravimetry. The thermal decomposition of the intercalates takes place in three stages: dehydration, removal of amines, and condensation of the hydrogenphosphate to pyrophosphate. The increase in the α-TiP interlayer distance (7.56×102 pm) during the intercalation was followed by x-ray powder diffraction. The standard enthalpy (δrHmo) involved in the overall reaction O3PO-H + RNH2→ O3P-O-+H3NR, which was determined by reaction-dissolution calorimetry, correlates linearly with the number of carbons in the alkyl chain and with the interlamellar distance. An intercalation mechanism is proposed, starting from the amine protonation by POH groups and its insertion between the sheets. An increase in enthalpy of -2.67 and +2.56 kJ mol-1 or -1.24 and +1.20 kJ mol-1/102 pm for each CH2 group of the n-alkyl chain in dce and water, respectively, for this series of amines is proposed. © 1991 VCH Publishers, Inc.214146