In this three-year U.S.-Yugoslav cooperative research project in theoretical chemistry between Nada Miljevic at the Boris Kidrich Institute for Nuclear Science, Belgrade, and Alexander Van Hook at the University of Tennessee, the investigators will study isotope effects in solution. In particular, they propose to examine clay-mineral systems, carbon disulfide-methanol systems, and aqueous solutions. In addition to advancing knowledge on thermodynamics of solutions, these studies could have practical applications in industrial, geochemical and agricultural operations. The U.S. and Yugoslav scientists have a previous history of successful collaboration on these topics. This project was approved by the U.S.-Yugoslav Joint Board on Cooperation in Science and Technology and is supported through a joint fund consisting of matching contributions from the governments of the United States and Yugoslavia. The U.S. contribution is provided annually by the Department of State. No NSF funds are involved. Grants are made to the principal scientific institution in Yugoslavia, but include dollar funds for U.S. scientist travel to Yugoslavia and for Yugoslav scientists' living expenses in the U.S.