Mr M e Glung, Effect of Temperature on Ionization, etc. 191 



A Preliminary Account of an Investigation of the effect of 

 Temperature on the Ionization produced in Gases by the action of 

 Rontgen Rays. By R. K. M c Clung, Trinity College, ' 1851 Exhibi- 

 tion' Scholar. 



[Read 4 May 1903.] 



During the course of an investigation of the effect of tempera- 

 ture on the recombination of ions produced by Rontgen rays, the 

 question of how the ionization was affected by the temperature of 

 the gas arose, and it was thought advisable to make a separate 

 investigation of this question. A number of measurements were 

 made on it, using the apparatus which was used in the experi- 

 ments on the recombination of the ions, but in this apparatus the 

 air which was being experimented upon was free to expand into 

 the outside air when heated. Since the amount of ionization 

 depends upon the density of the gas, it was considered necessary 

 to confirm these results obtained by making some experiments, 

 using an air-tight vessel, so that the gas might be kept at a 

 constant density, In this paper a preliminary account is given of 

 some of these experiments which are still in progress. 



Description of Testing Apparatus. 



The chief difficult}^ which arose at the outset of the investiga- 

 tion was that of obtaining a metal vessel, of necessity containing 

 joints, which must be made gas-tight, and which would stand both 

 temperature and pressure. After trying several methods, the 

 apparatus which is shown in detail in fig. 1 was adopted, and 

 proved very satisfactory. 



A B is a circular brass cylinder about 7 cms. in diameter and 

 24 cms. in length. FF is a thick brass flange brazed on the end 

 of the cylinder. P is an aluminium plate 6 mm. in thickness, 

 which is recessed at the centre to a depth of 5 mm. in order to 

 allow the Rontgen rays to pass into the cylinder without much 

 absorption. This plate is made to fit closely to the flange FF. 

 Between the plate and the flange is placed a lead wire, as shown in 



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