The crystal structures of the normal fatty acids of low molecular weight have been rather neglected until recently. Formic acid and acetic acid occur in the solid as hydrogen-bonded linear polymers, while several acids with eleven or more carbon atoms per molecule exist in the solid as dimers. The melting points of these acids, when plotted against number of carbon atoms, fall on two rather similar curves for even and odd numbers of carbon atoms, respectively, each with a minimum near five carbon atoms. These facts and hope of explaining the melting-point behavior led us to examine the structures of propionic and butyric acid crystals. These crystals have different structures, but both contain dimers.

Tables of the electron pressure and kinetic energy for a partially degenerate, relativistic, ideal electron gas are computed by numerical integration using an IBM 7090 electronic calculator. These are given in terms of log10(B) and log10(0), where B is the ratio of the temperature to the rest mass of the electron and (O) is proportional to the numerical density of electrons. The tables include values of T from 5 million to 400 billion degrees and cover the range of electron densities from the region of a perfect gas to the region of complete degeneracy.