In this paper，further simplifications are suggested for the two-fraction method based on the solubility function and the treatment of fractionation data by using Tung functiorr which were proposed by the present authors in previous publications．The evaluation of the distribution parameters for a fraction from two intrinsic vis-cosity measurements in a good solvent and in a θ-solvent is shown to be not practical

because the required precision is not attainable in ordinary measurements． A new ap-proximation is suggested by taking the phase separation parameter Q to be equal to the volume ratio R of the concentrated and dilute phases．Then，the distribution para- meters for the two-fraction method can be readily evaluated． Actual calculations show that the distribution parameters thus calculated is not very sensitive to the value of Q taken，and therefore this approximation is iustified as a tentative simplification of the two．fraction method for the determination of molecular weight distributions．In the treatment of ordinary fractionation data by means of Tung function，all fractions except the first and the last ones can be approximated by a straight line for the integral distribution curve．The line passes through the points M (1＝1-2)＝Mn，M(1＝0)＝1-2Mn which corresponds roughly to a straight line with equal slope as the Tung function at M1-2 with b=2.7—3.0．This leads to a considerable saving in corn-putation but very slight difference to the result．The suggested simplifications have been applied to a sample of PMMA．The in-tegral distribution curve obtained by the suggested method are closer to the actual one obtained by sedmentation rate method than the usual Schulz-Dinlinger treatment．