ABSTRACT
It was shown by Ernest Rutherford and Soddy in 1903 that the radium emanation was condensed from the gases with which it was mixed at a temperature of about -150º. From observations of the range of temperature of condensation and volatilisation it was concluded that the condensed emanation exerted a sensible vapour pressure. Sir William Ramsay and Cameron have pointed out that the emanation, condensed in a glass tube kept at the temperature of liquid air, can be removed by continuous pumping, thus indicating appreciable vapour pressure even at that low temperature. In the initial experiments of Rutherford and Soddy only very small quantities of radium were available, and the partial pressure of the emanation in the experiments was exceedingly small. If the capillary tube containing pure emanation is quickly placed in the pentane bath, cooled well below the temperature of initial condensation, under a microscope small drops of liquid emanation are seen on the walls of the capillary.
