﻿338 Mr. A. Fleck on the Condensation of 



on neon and metaneon, they would have the same temperature 

 of condensation *. 



In a paper communicated to Section A of the British 

 Association meeting in Birmingham, September 1913,. 

 Ashton brought forward evidence to show that atmospheric 

 neon consisted of two elements of different atomic w r eight. 

 These two gases could not be separated from one another by 

 means of fractional condensation, but the separation could 

 be effected by diffusion. The atomic weight of the new gas 

 was found by the positive ray method to be 22. 



Experiments at Atmospheric Pressure. 



The difference found by Rutherford and Soddy in the 

 behaviour of the two emanations when subjected to low 

 temperatures is definite enough, but it has to be remembered 

 that the concentration of radium emanation required to 

 produce a given ionization effect must be approximately 

 6000 times the concentration of thorium emanation to produce 

 the same effect. The only possible way therefore to test 

 whether the two emanations have exactly the same conden- 

 sation point, is to have them thoroughly mixed before being 

 cooled to the low temperature. The methods used in the 

 first series of experiments were the same in principle as 

 those used by Rutherford and Soddy, in which the emanation 

 was mixed with air at atmospheric pressure. The apparatus 

 finally used is shown in figure 1. An 80 feet gas-cylinder, A, 

 was used which was in direct connexion with a glass T-piece, B, 

 the vertical limb of w T hich dipped below the water in the glass 

 jar. There were two marks on the stem of the T-piece, M x 

 and M 2 , and the level of the water in the jar was kept at M L 

 whilst the level of the water in the tube was adjusted, by 

 altering the pressure of the escaping gas, to M 2 . Immedi- 

 ately beyond the T-piece was a short length of capillary 

 tube, C, so that by maintaining a constant pressure at B, 

 the amount of gas passing through C was directly pro- 

 portional to the time. The capillary tube was followed by 

 a tube containing phosphorus pentoxide, and then by a 

 piece of wide tube containing the source of thorium 

 emanation. This was a strong preparation of radio-thorium 

 which had been separated from a mixture of radium and 

 mesothorium. Gas coming through the apparatus was 

 therefore mixed with a constant quantity of thorium 

 emanation after the equilibrium amount of emanation had 

 been removed. Beyond the active preparation was a three- 

 way tap, one limb of which went directly to the outer 

 * Soddy, ' Chemistry of the Eadio-Elements/ pt. ii. p. 36. 



