The theory of solubility proposed by Jhon and Kihara has been tested and applied to various systems. In the present paper, the systems are the solubilities of gases such as $Ar,\;H_2,\;N_2,\;O_2,\;CO_2,\;CH_4,\;and\;C_2H_6$ in liquid benzene and carbon disulfide, those of solids iodine and naphthalene in the nonaqueous solvents, and those of gases $H_2,\;N_2,\;O_2,\;Ar,\;CH_4,\;and\;C_2H_4$ in the electrolyte solutions. The theoretical values of solubilities are in good agreement with the experimental data in the literature.