New experimental vapor pressures and vaporization enthalpies of the ionic liquids $$ [ {\text{C}}_{2} {\text{mim][CF}}_{3} {\text{CO}}_{2} ] $$ [C2mim][CF3CO2] and $$ [ {\text{C}}_{4} {\text{mim][CF}}_{3} {\text{CO}}_{2} ] $$ [C4mim][CF3CO2] have been measured by the QCM method. The solution enthalpies of these ionic liquids were measured by using high-precision solution calorimetry and were used for calculation the aqueous enthalpy of formation $$ \Delta_{\text{f}} H_{\text{m}}^{ \circ } ({\text{CF}}_{ 3} {\text{CO}}_{2}^{ - } ,_{{}} {\text{aq}}) $$ ΔfHm∘(CF3CO2-,aq) of the anion for combination with quantum-chemical results. The solubility parameters of the ILs under study have been derived from experimental $$ \Delta_{\text{l}}^{\text{g}} H_{\text{m}}^{ \circ } $$ ΔlgHm∘ (298.15 K) values and were used for estimation of miscibility of some common solutes with $$ [ {\text{C}}_{n} {\text{mim][CF}}_{3} {\text{CO}}_{2} ] $$ [Cnmim][CF3CO2] .