Measurement of large Partition Coefficients by Interchange Extraction CALVIN GQLUMBICA N D SOL WELLER Research and Developpaent Branch, O m e of Synthetic Liqu.id Fuels, Bruceton, Pa. A satisfactory method for measuring large (or small) partition coefficients is described. The method is essentially a means of increasing the concentration of solute i n the denser (or lighter) phase until measurable values are obtained. The technique by which this can be accomplished is termed “interchange extraction.” The method was subjected to precise mathematical analysis, which led to the development of an equation relating the partition coefficient to the number of extraction stages. The equation was tested by the experimental determination of the partition coefficients of o-phenylphenol in two systems.
T
HI< partition coefficient of a compound is usually a readily measurable quantity that is useful as a supplementary constant for identification purposes (I), for devising isolation schemes
determined hy any convenient method. The partition coefficient is then calculated by Equation 2, the development of which is given in the following section.
( 4 ) , and, when the compound in question bas an acidic or basic function, for calculation of acid or base strerigth (3). Partition coefficient, h, is usually defined by the expression concentration of solute in lighter phase concentration of.solute in denser phase It may be measured in two ways: by determining the conccntratioir of solute in one phase before and after equilibration, and by measuring the concentration of the solute in each phase after equilibration. Both methods are usually inadequate when t,he partition coefficient is very large or very small (>lo0 or
