[ (;55 ] 



LXXXn. 11 w Relation between the Rate of Recombination of 

 Ions in ^lir and the Temperature of the Air. By R. K. 

 McCluxg, M.A.(3IcGill), B.A. (Cantab.), Trinity College, 

 Cambridge, 1851 Exhibition Scholar^. 



IN a previous paper (Phil. Mag. March 1902) I gave the results 

 of an investigation of the relation between the pressure 

 of the air and the rate of recombination of the ions in the 

 air which had been ionized by Rontgen rays. The experi- 

 ments described in that paper were performed at the ordinary 

 temperature of the room. It was thought that it would be 

 of interest to pursue this investigation further, and ascertain 

 wjiat effect a change of temperature of the air would have 

 upon the rate at which the ions recombine. 



Prof. Rutherford investigated experimentally the rate of 

 recombination of ions in gases at the ordinary temperature 

 and pressure of the surrounding air (Phil. x\iag. Nov. 1897), 

 and he verified the equation 



dn 



d~t 



— an 



(1) 



which represents the law of recombination of the gaseous 

 ions. 



It was shown by the author, in the paper referred to above, 

 that over a considerable range of pressures, both above and 

 below atmospheric pressure, the same law holds true. The 

 present series of experiments were therefore undertaken 

 with the object of ascertaining, in the first place, whether this 

 same law of recombination holds at various temperatures of 

 the air, and, secondly, what effect a change of temperature of 

 the gas has upon the value of the coefficient of recombina- 

 tion a. 



The method employed in the previous investigation was 

 adopted in the present instance. It was necessary, however, 

 to modify the apparatus somewhat in certain details, as in 

 this case it was to be subjected to fairly high temperatures in 

 the course of the experiments. The following apparatus was 

 therefore employed. 



Description of Apparatus. 



The general arrangement of the apparatus is shown in 

 fig. 1. The Rontgen-ray bulb and the induction-coil which 

 run it were, us usual, inclosed in a lead-covered box 

 as a shield, and the rays were allowed to emerge through a 



* Communicated by Prof. J. J. Thomson. 



