The temperature coefficient of the surface tension of pure liquid metals

The surface tensions of liquid Fe, Co, Ni, Cu, Ag, Zn, Pb, Cd, and Sn have been measured by the sessile droplet method and/or the levitated droplet method over wide ranges of temperature. The values of surface tension obtained by the levitated droplet method have always been found to be higher than those measured by the sessile droplet method, a result which is attributed to decreased droplet contamination with the containerless levitation method. Negative temperature coefficients of surface tension have been obtained for all of the metals investigated in this work. Based on a literature survey of the available experimental data, it is shown that the values of both surface tension and the temperature coefficient are influenced in a systematic manner by the presence of surface active impurities. On this basis, positive values of the temperature coefficient of surface tension for liquid Zn and Cd found in the literature may be explained in terms of impurity effects which tend to be particularly pronounced in volatile metals. Formerly Research Associate in the Department of Metallurgy and Materials Science, University of Toronto