The Contact Electromotive Force between the Solid and Liquid Phases of the Same Metal and between the Outgassed Surfaces of two Dissimilar Metals

Abstract

Change in contact e.m.f.at the melting point of three low melting point metals. —Measurements were made on tin, Wood's metal and a Sn-Pb alloy (1/4th Pb) in comparison with a nickel surface, using the standard Kelvin null method. The metal, previously purified electrolytically, was melted in vacuum and then run into a cup below the nickel surface. No evidence of a sudden change of contact potential at the melting point was observed. However even with vacua of the order of 5×${10}^{-6\mathrm{}}$ to ${10}^{-6\mathrm{}}$ mm, a residual gas effect caused the contact potential on cooling to be less than on heating, in one case by.14 volt, and this may have masked a slight jump. It is probable, however, that with the metals studied the change cannot be more than.005 volt.