On the Compressibilities of Simple Metals

An isothermal equation of state is derived from the Coulomb virial theorem for ``simple'' metals consisting of imperturbable (i.e., invariant) kernels embedded in a uniform sea of valence (e.g., s) electrons. Comparison with experiment at room temperature gives good agreement for the alkali and alkaline earth metals, but is understandably erratic for other groups. The compressibility is simply related to the heat of formation of the normal gaseous ion kernel.