Abstract: A solution of groups technique was developed for use with fluctuation solution theory. The general expressions for calculation of pressure and chemical potential changes from some fixed reference states have been shown. A new corresponding states theory correlation for direct correlation function integrals was proposed and used with the group contribution technique for calculation of pressure changes during compression for several n-alkanes and methanol. This work gives a detailed analysis of the RISM theory of liquids. Shown are new results for perturbation theory and a generalized compressibility theorem for RISM fluids. The use of the RISM theory for calculation of thermodynamic properties of real fluids also is given. The use of hard sphere reference fluids for development of equations of state has been explored. A generalized hard sphere equation of state was developed. It was shown that the most accurate hard sphere equation of state is not the best reference system for construction of a liquid phase equation of state of the van der Waals form. Dissertation Discovery Company and University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Thermodynamic Properties of Multicomponent Mixtures From the Solution of Groups Approach to Direct Correlation Function Solution Theory" by John Charles Telotte, was obtained from University of Florida and is being sold with permission from the author. A digital copy of this work may also be found in the university's institutional repository, IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.