Vapour pressures and vaporization enthalpies of tetraalkylphosphonium ionic liquids with [PF6], [NTf2](-), Cl-, and Br anions have been measured by using quartz-crystal microbalance and thermogravimetry. Chain-length dependences of the vaporization enthalpies have been established and used for validation of experimental data. Quantification of Coulomb and dispersion forces was performed by comparison with vaporization enthalpies of alkanes and trialkylphosphines. (C) 2018 Elsevier Ltd.