The solubility of fatty acids and alcohols in water at 25� has been measured by a new technique involving a film balance. For both, the logarithm of the solubility varies linearly with chain length, and the deviation from this for fatty acids as found by earlier workers is shown to be due to ionization of the acids in water. The ionization constant of tetradecanoic acid in water at 25� was estimated to be 1.26 x 10-5.