抄録
(a) The temperature coefficient of the isothermal compressibility (1⁄βT)(dβT⁄dT) and the coefficient of thermal expansion α have been computed for liquids employing Lennard-Jones and Devonshire’s equation of state as improved by Wentorf, Buehler, Hirschfelder and Curtiss and employing the numerical tables by these authors. The computed value of the ratio of these two coefficients is about 6.5 at temperatures corresponding to 0.9 Tb, where Tb means the boiling points. This gives a rough explanation of the Rao’s relation between the temperature coefficient of the adiabatic compressibility βS and the coefficient of thermal expansion α; i.e., (1⁄βs)(dβs⁄dT)=7α. (b) Reexamination of Rao’s relation has been performed on many organic liquids, some liquified gases, and some molten metals employing existing ultrasonic velocity data. The ratios (1⁄βs)(dβs⁄dT):α are about 7 in organic liquids, about 5 in liquified gases and rather scattered in molten metals.
