The sublimation of metals at low pressures

Abstract

Many metals have been found to exhibit evidences of volatility at temperatures considerably below their melting points. As long ago as 1872, Merget demonstrated that frozen mercury volatilised perceptibly in air in course of time. Demarçay, in 1882, conducted similar experiments in vacuo and found that cadmium evaporated sensibly at as low a temperature as 160°, zinc at 184°, and lead and tin at 360° C. In 1887, Zenghelio obtained evidence of the volatility of lead, copper, zinc, etc., even at room temperatures. Spring, in 1894, working at atmospheric pressure, showed that zinc was appreciably volatile at 300°, and cadmium and copper'at 500°. Roberts-Austen and Merrett, in some unpublished experiments at the Royal Mint, in 1896, detected the volatility of cadmium and zinc at 100° in vacuo, while Krafft in 1903 and 1905 investigated in some detail the volatilisation of a number of metals at low pressures. Rosenhain, at the National Physical Laboratory, has obtained beautiful crystals of sublimed zinc by heating a piece of zinc to 300° C. for some weeks in a glass tube containing hydrogen at atmospheric pressure. The notable phenomena of the interdiffusion of metals, with which Roberts-Austen’s name is associated, provide, of course, additional evidence of the vapour pressure that solid metals exert even at ordinary temperatures.