1.The molecular weight dependence of the distribution of polymer molecules between the coacervate and the dilute phases on the phase separation of polymethylmethacrylate-acetone-methanol system has been proved to follow the relation first derived by Flory for binary systems:
f"_j=Qe^σM_j
where f"_j and f'_j are the weight fractions of the polymer molecules of molecular weight M_j in the coacervate and in the dilute phases respectively,while Q andσare parameters.The value of Q found experimentally is not equal to the volume ratio of the two phases as theory for binary systems demands.The molecular weight distributions of the original sample and the coacervate after phase separation were determined by the sedimentation velocity method in a θ-solvent.2.The width of molecular weight distribution of a fraction is found to decrease repeated refractionations.The widely circulated opinion that it is not very effecafter second refractionation is not justified by the present findings.3.A simple approximate method based on the solubility function is suggested for the determination of molecular weight distributions.The method involves only two phase separation experiments and five precise determinations of intrinsic viscosity.