The Structure of Liquid Potassium

The method of Wall for calculating the free volume per atom in a liquid has been applied to liquid potassium, using the atomic distribution curves for potassium at 70°C and at 395°C given by Thomas and Gingrich. From the free volumes at these temperatures, the entropies of the liquid at its melting point and at its boiling point are obtained. These values, together with the entropy of solid potassium at its melting point and the entropy of potassium vapor at its boiling point, supply the entropies of fusion and of vaporization. Hence the latent heat of fusion is calculated as 2.06 $\frac{\mathrm{kj}}{\mathrm{mol}}$, and the latent heat of vaporization is calculated as 87.5 $\frac{\mathrm{kj}}{\mathrm{mol}}$. These values are to be compared with the observed values 2.38 $\frac{\mathrm{kj}}{\mathrm{mol}}$ and 84.0 $\frac{\mathrm{kj}}{\mathrm{mol}}$, respectively.