The Dubinin-Radushkevich/Dubinin-Astakhov (DR/DA) adsorption equations have been modified with the aim to eliminate the thermodynamic incorrect behavior of these equations in the Henry region and in the vicinity of the equilibrium saturated vapor pressure. The expressions for heat and entropy of adsorption are obtained from the proposed modified DR/DA equations. These new equations, which do not include additional empirical parameters, have been evaluated on adsorption systems measured over a wide range of pressure and temperatures. The temperature dependence of the parameters has been analyzed.