\Teasurements have been made of the vapour pressure of polystyrene solutions in toluene and methyl ethyl ketone at different temperatures. The heat of dilution of polystyrene by toluene is zero. The results are discussed in relation t o the existing theories of the free energy and entropy of dilution of polymers.

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Measurements of the intrinsic viscosity of polystyrene fractions in five solvents at 25' C are in accord with the viscosity-molecular weight relationship [q] = K M a ; a attains a limiting value of 0.73 in good solvents. The decrease in o! as the solvent becomes poorer is accompanied by a corresponding increase in K and these two magnitudes are related. The empirical equation ( I ) relating the intrinsic viscosity [q]with the molecular weight M is now well established for many systems K and a are constants characteristic of the polymer-solvent system and weight determination the values of K and a are important in assessing the influence of solvent on the configuration of the polymer chain. The present measurements refer to the viscosity-molecular weight relationships for polystyrene fractions (used for osmotic pressure measurements Huggins, J .