The recovery of organic solvents containing water less than 7% from a miaturo of acetone, ethyl alcohol, ethyl acetate and water is impossible, according to the principle of rectification analysis, because of the formation of azeotropic distillates. Experiments show that the dehydration of these organic solvents could be made effective by the addition of anhydrous calcium chloride. Explaination is given by treating the data of salt effect on vapor-liquid equilibrium in terms of thermodynamics of solutions. The mochainsm of dehydration by anhydrous calcium chloride is discussed, and a suitable technique for the dehydration of organic solvents is provided.