A new model for gas solubility, which is a modification of Pierotti's theory, has been developed. According to this model, the solute of a dilute solution can be considered as a perfect quasi-gas and Henry's constant is the product of the pressure of 1 mol perfect gas and a Boltzmann's factor, which is dependent on the internal pressure of the solvent around the solute molecules. The testing results for the solubility data of some gases in organic solvents and polymers show that the model can satisfactorily be used to describe the variation of Henry's constants with the temperature and the calculated partial molar thermodynamic functions for formation of the dilute solution are also consistent with the experimental values.

Key words: INTERNAL PRESSURE, GAS CONSTANT, DILUTE SOLUTION, GASES, SOLUBILITY, SOLUTION THEORY, HENRY'S CONSTANT, THERMODYNAMIC FUNCTION