Using previously published values of the enthalpies of solvation of some derivatives of three-coordinated phosphorus compounds, the contributions of the non-specific solvation enthalpies in the general solvation effect in benzene, p-xylene, methanol and pyridine have been calculated. Taking into account the known possibility of intramolecular complex formation between halogenated derivatives of P-III and pyridine, the magnitudes of specific interaction enthalpies for PCl3, PBr3, (EtO)(2)PCl, [GRAPHICS] PCl and [GRAPHICS] PBr were determinated. Thermodynamic parameters of complex formation between cyclic chlorophosphites and 1-dimethylamino-3,3-dimethyl-propan-2-on have been obtained and are discussed.