Nuclear Spin and Symmetry Effects in the Heat Capacity of Ethane Gas

The heat capacity of ethane gas has been calculated for a number of values of the internal potential barrier from zero to high barriers. Detailed account of the presence of noncombining species and of the exact nuclear spin statistical weights was taken. It was found that down to temperatures at least as low as 90°K these phenomena are entirely unimportant and that the partition function calculated in the usual way is correct. It is concluded that the observed experimental data are best explained by the assumption of a high restricting potential. Tables of statistical weights for the rotational levels of C2H6 and C2D6 are given.