Abstract: The completely unmixing of the liquid on the plates was assumed by Lewis to derive the theoretical relation between the plate efficiency and local efficiency. This assumption is not true for the actual cases. In the present paper, introducing a conception of the liquid pool, suggested early by Kirschbaum, to express the mixibility of the liquid on the plates. Using this conception the three equations were derived for three cases as in the Lewiss paper. It is interested to note that the first two cases, as k approaches infinity, can be reduced to the Lewiss form, and as k=l, equal to the Murphrees plate efficiency. These derived equations are the intermediate between the Lewis and Murphree equation, which represent the extremes of actual condition. In this paper, a method for estimating the point efficiency is also given, which is resonablly shown by the two examples. However, no further experimental data are available to demonstrate the utility.