6±S 



Mr. G. Shearer on the 



Table IV. compares the ionization in H 2 with that in SeH 2 . 

 When we consider that values for SeH 2 , and not for AsH 3 , 

 have been used, the agreement between the two entries in 

 the last column indicates that Beatty's results could be 



Fig. 1. 



























. 





l-e- H 











-*- n 2 

 h*SeH 















































































X /p m Al. 

 Table IV. 



80 



Rays. 



- in Al. 

 9 



ff r (Beatty). 



^(Beatty). 



H 2 

 SeH 2 * 



Fe 



88-5 



•00571 ^ 



30-31 







Cu 



47 . 7 



•00573 1 Mean 

 •00570 | -00572 

 •00573 ) 



29-2 



Mean 





Zn 



As 



39-4 

 22-5 





'30-0 



•00019 



Se 



18-9 





30-6^ 







Sn 



1-6 



•0400 



250 



•00016 



explained completely by the presence of a small quantity of 

 arseniuretted hydrogen. The amount of the impurity would 

 require to be about one part in 6000. It would seem, then, 

 that the sudden rise in the relative ionization of hydrogen 

 between arsenic rays and tin rays was more probably due to 

 the presence of a small quantity of AsH 3 , and this is all the 

 more likely when we consider that the hydrogen used by 

 Beatty was prepared from zinc and sulphuric acid, in both 

 of which arsenic is a common impurity which it is difficult 

 to remove. In the preparation of his hydrogen Beatty took 

 precautions to obtain the gas in a pure state, but beyond 

 passing the gas through liquid air, took no special steps to 



