Number of Ions produced by Beta Rays from Radium C. 551 



electric field and that by a foreign ionizing agent, especially 

 as some properties o£ the gaseous ions (e. g., the formation 

 of clusters) have also been found in the Kanalstrahlen. 



Thus we are inclined to believe that, under the right 

 conditions, multiply-charged positive ions may be generated 

 not only by Rontgen rays but also by any other ionizer. 



Having just written this paper, we see in the last number 

 of your Magazine a paper by J. S. Townsend on the same 

 subject. We cannot but say that his views are in perfect 

 accordance with ours. Yours truly 



J. Franck and W. Westphal. 



Berlin, 

 Physikalisclies Institut der Universitat, 



July 1911. 

 



LTI. On the Number of Ions produced by the Beta Rays and 

 by the Gamma Rays from Radium C. By A. S. Eve, M.A., 

 B.Sc, McGitl University^ Montreal*. 



IN a previous paper f, an account has been given of the 

 determination of the coefficient of absorption by air of 

 the ft rays from radium C, and a mean value //, = e 004 cm. -1 

 was obtained, suggesting an average path of the ft rays of 

 2*5 metres in air at atmospheric pressure J. This led to an 

 estimate of the coefficient of absorption of the y rays in air, 

 fjj = -000032 cm. -1 , somewhat lower than that given bv the 

 ratio /x7D = '034 oi McClelland, whence /x' = -000044," and 

 yet smaller than the value derived from /x'/D = # 04, found by 

 Soddy and Russell. In the work that follows, the inter- 

 mediate value fju' ■= '000044 has been adopted. The value 

 tor e, the electronic charge, has been taken as 4 9 x 10 " 10 

 elec'rostatic unit. 



In the present paper, experiments are described which lead 

 to the evaluation of the total number of ions produced by 

 the ft rays, and of those produced by the y rays, from one 

 curie of radium C ; that is, the amount of radium O in 

 equilibrium with one gramme of radium. The heating 

 effects of the ft and y rays may thus be calculated, and also 

 the average number of ions produced by one ft particle, both 

 for its average path, and for 1 cm. of path. Corresponding 



* Communicated bv the Author, 

 t Phil. Mag. July 1911. 



\ At short ranges with the active deposit of radium on aluminium 

 foil 1 have recently found /x=-012 cm. -1 . In this case RaB was also 

 .sending (i rays to the electroscope. 



2 U 2 



