It has been established which equations of state describe exactly enthalpy and entropy of hydrogen sulfide, carbon dioxide and their mixtures at the temperature and pressure ranges occurring in installations for removal of gases by their absorption in aqueous solutions of alkanoamines. Thermodynamic (p-H-T) properties of gases were described by the difference of mole enthalpy under pressure P and 1 atm pressure at the constant temperature (H-P-H-1)(T). Thermodynamic (p-S-T) properties of gases were described by the difference of mole entropy under pressure P and 1 atm pressure at the constant temperature (S-P-S-1)(T).