Surface Tension of Sodium

We have determined the surface tension of molten sodium, by a modified flat drop method, in a high vacuum. In doing so we have used Worthington's correction formula $\sigma =\frac{{\mathrm{}(K-k)\mathrm{}}^2\rho }{2}\frac{1.641L}{1.641L+(K-k)\mathrm{}}.$ From the best mean straight line through the experimental points the surface tension at 100°C and at 250°C was found to be 206.4 and 199.5 dynes per cm respectively. Hence the temperature gradient is -4.6×${10}^{-2\mathrm{}}$ dyne per cm per degree. Consequently, the average value of $k$, in the Eötvös relation, was found to be 0.067 and we conclude that the molecules in liquid sodium are polyatomic. We base the accuracy of our results on the high vacuum maintained throughout the period of experimentation. That both the apparatus and the liquid metal were thoroughly outgassed was proven by the fact that the McLeod gauge gave no reading (i.e. a gas pressure ${10}^{-6\mathrm{}}$ mm Hg) even while sodium was being distilled over into the cup. Reproduction of concordant results argues against the formation of films on the sodium, adsorbed gases or reaction of the sodium with the glass.