Fractionation of continuously distributed homologous mixtures is described in terms of molecular distributions. The concepts apply to phase equilibrium in vapor-liquid hydrocarbon mixtures and sol-gel polymer mixtures. Models of both differential and finite phase-equilibrium separations are presented when the partition coefficient for the equilibrium distributions is given. Analytical solutions for the distributions, including a similarity solution for a differential fractionation, can be formed. A differential fractionation solution compares satisfactorily with experimental data.