The n-butane/water distribution constant is one of the key parameters in determining the extraction, efficiency. Experimental results on, 34 organic compounds illustrated that a fundamental, linear relationship, exists between the distribution constant, and the aqueous solubility of the solute. The relationship can be broadly applied to many different classes of chemical compounds as well as to many different solvent extraction systems. The linear equation obtained by a regression method allows one to estimate,the distribution constant,and predict the result of butane extraction if the aqueous solubility of certain solute is available.