Properties of Solid and Liquid Solutions of Argon and Krypton

The vapour pressure P of solid and liquid mixtures of argon and krypton of a number of different compositions has been measured over a temperature ( T ) range which includes the `melting' and `freezing' points of the mixtures. The solid-liquid phase-equilibrium diagram has been deduced by observation of discontinuities in slope of (log P , 1/ T ) graphs. The measurements show that argon and krypton are completely soluble in the liquid and solid states and that the solid solutions exhibit a positive deviation from ideality. The solid solution data are compared with theory. Although the experimental results are not in complete agreement with any of the theories considered, the cell theory predicts approximately the observed magnitude of the deviations from ideality of the vapour pressure.