An iterative inversion procedure is used to obtain the effective isotropic part of the pair-interaction potential for some pure refrigerants from the proposed correlation function for the zero density collision integrals of viscosity. The Lennard-Jones (LF12-6) potential energy function is used as the initial model potential required by the method. Over a range of reduced temperature extending from 1 to 100, this measured potential can be used in the calculation of the orientation-averaged viscosity collision integrals and the dimensionless ratios which are essential to calculate other transport properties.