Simplified calculations of theoretical distributions and partition coefficients for counter-current extractions.

The recent paper of Williamson and Craig (1) should advance the use of counter-current extraction processes as a potent laboratory implement. The general usefulness of the method in research laboratories is due to the work of Martin and Synge (2), who showed that the process could be expressed mathematically as a binomial expansion, and to the development of the method and a compact apparatus by Craig (3). In applications in these laboratories it became necessary to plot a number of theoretical distribution curves. To lighten a tedious calculation task, a method was developed which lent itself to the use of an ordinary adding machine, permitting the calculation of a complete distribution in a very short time. The determination of the partition coefficient from the peak of an experimental distribution curve was also developed as a corollary. The method and calculated values for a series of partition coefficients for both eight and twenty-four transfer processes are presented, since the availability of the data and the ease of calculating new data as needed should make laboratory scale counter-current extraction more generally useful. The general term of the expansion of the binomial