The cavity formation energy (CFE) which is equivalent to the free energy co
st of insertion of a hard sphere solute in a hard sphere solvent, Is calcul
ated for benzene, carbon tetrachloride and water at 298 K. The solubility o
f non-polar gases He, Ne, Ar, Kr, Xe, and Rn in benzene, carbon tetrachlori
de and water has been calculated with this CFE. The results agree well with
the experimental values of Henry's law constant and molar free energy of s
olution. The method has also been used to calculate the hard sphere diamete
r of the solvents.