Different thermodynamic parameters are estimated from volume expansion coefficient, , for a number of N-(p-n-alkoxy benzylidene)-p-n-alkyl anilines, nO.m compounds in isotropic phase at TIN+5 degrees C. The parameters like intermolecular free length, Lf, and molecular radius, Mr, are also computed from density, sound velocity, and refractive index for these nO.m compounds for which the data are available in the literature. The results are discussed in light of these parameters' variations with temperature in a particular phase in a liquid-crystal molecule and in a homologous series. The nature of molecular free length and molecular radius is analyzed and discussed with respect to the different expressions used for the estimation of these parameters and the reasons for their deviations in values from one method to the other.