COSMO-RS is a still quite novel method for the a priori prediction of chemical potentials, activity coefficients and vapor pressures of almost arbitrary chemical compounds in pure liquid solvents and mixtures. In contrast to the widely used group contribution methods COSMO-RS gets the information about the intermolecular interactions from uni-molecular quantum chemical calculations on the compounds and thus it is far less dependent on experimental data. Hence COSMO-RS is an efficient alternative to group contribution methods on the one side and to the Monte-Carlo and Molecular Dynamics simulations on the other side. Apart from a few disadvantages it has a lot of systematic advantages. The greatest strengths are the broad applicability and extrapolation power of the method, and the systematic physical insight into the mixture behavior of the systems, which COSMO-RS opens by its sound physical basis. Thus complicated or rare compounds can be treated and differences between isomers can be resolved.

Beyond the basic features regarding activity coefficients, vapor pressures, and enthalpies of fluid systems, COSMO-RS can be applied to solid-liquid equilibria, to solubility in polymers, to ionic liquids and electrolytes, to pKa-prediction, to adsorption phenomena and physiological partitioning, reaction thermodynamics, micelle and bio-membrane distribution, chromatographic retention times, crystal face polarities, and many other problems of physical chemistry which have to do with liquid phase equilibria.