In the previous communications we have used the value of the partial specific volume, v2, of polystyrene, PS, derived by Hooker et al (1) for determining the molecular weight of the polymer by light scattering (2), viscosity slope constant (3,4) and the excluded volume parameter (5,6). The partial specific volume is a characteristic parameter of the polymer. This parameter depends on both intra- and inter molecular segment-segment interactions. Hence, several reports (7-11) considered the dependence of v2 on the solvent, concentration and temperature. Hence, specific volume measurements on solutions of PS sample in tetralin, Tet., at different temperatures and mass fractions were performed.