The standard molar enthalpies of formation of crystalline tetraalkylammonium halides, Delta H-f degrees(R4NX, c), R = Me, Et, Pr, Bu and X = Cl, Br, I, and the corresponding lattice energies, U-L(R4NX) were obtained from the literature as far as available for T = 298.15 K. From consistent values of these two quantities and values for Delta H-f degrees(X , g) the standard molar enthalpies of formation of the gaseous cations were obtained from Delta H-f degrees(R4N+, g) = Delta H-f degrees(R4NX, c) + U-L(R4NX) + 2RT degrees - Delta H-f degrees(X , g). The value for the hitherto unreported Delta H-f degrees(Pr4N+, g) = (307 +/- 7) kJ . mol is here derived. The value for the absolute standard molar enthalpy of hydration is Delta H-h degrees(R4N+, aq) -210 kJ . mol (1), but may have an appreciable uncertainty, reflecting that of Delta H-f degrees(R4N+, aq), obtained from interpolation of values for the Me, Et, and Bu analogues. (C) 2014 Elsevier Ltd. All rights reserved.