The surface tension of liquid sodium and liquid potassium

Abstract

A vertical-plate balance has been used to measure the surface tension and temperature coefficient of surface tension of liquid sodium and potassium. A value of 200.2�0.6 dyn cm-1 was obtained for the surface tension of liquid sodium at the melting point (97.8�), with a temperature coefficient of -0.11 dyn cm-1 deg-1. For liquid potassium the surface tension was found to be 110.3�1.0 dyn cm-1 at the melting point (64�), with a temperature coefficient of -0.06 dyn cm-1 deg-1. These results are compared with other published values of these quantities. A discussion, based on the statistical mechanics of a quasi-crystalline model of the liquid state, suggests that the chemical impurities present in the liquid metals are unlikely to have significantly increased the surface tension values above those of the pure metals.