Stable isotope studies. Annual progress report, March 1, 1980-February 28, 1981

Vapor pressures of 12CHF3, 13CHF3, and 12CDF3 were measured between -147 and -600C. The normal isotope effect of deuterium with a positive slope and the inverse isotope effect of 13C with a negative slope in the plot of T 1n(P'/P) vs 1/T are simultaneously explanable only in terms of a blue-shift in the C-H stretching frequency upon condensation of fluoroform molecules. Vapor pressures of 12CH3F, 13CH3F, and 12CD3F were also measured between -141 and -600C. The deuterium effect is a normal isotope effect with a large positive slope. The 13C effect is an inverse isotope effect with a slightly positive slope. A nitrogen-15 exchange column based on the pressurized NO/N2O3 system was constructed. New refluxer designs were developed. Two FORTRAN programs have been written for studies of differential isotope effect