[EVE] IONS PRODUCED BY THE BETA RAYS 75 
“== -0033 for air in the case of the 8 rays from radium C, — -019 
for the 6 rays of radium B. If there are equal numbers of 8 particles 
from these two products, it can be readily shown that the 6 rays from 
radium C alone gave 10-9 D/m corrected for air absorption, so that 
K/K’ = 27. This method involves some uncertainty. 
2. A glass tube containing -52 mg. of radium was placed at 75 cm. 
distance from the centre of the electroscope. The 8 rays gave 16-9, 
and the y rays -85 divisions/minute. The correction factor for air 
absorption is 1-25, and for the glass walls about 1-40. The @ rays 
from radium B were mainly absorbed. Thus 
K/K’ == X 1-28 X 1-40 = 35 
There is much uncertainty, however, in the correction for absorp- 
tion by the glass walls, and by the radium bromide of one-quarter of 
full strength. 
3. The most satisfactory method was the employment of a thin 
aluminium leaf (-0012 cm.), which had received a coating of the active 
deposit when negatively charged in the air above a solution of 11 mg. 
of radium bromide in a flask. Alternative readings for the 8 and 7 
rays, and for the y rays alone, were obtained, and the well known decay 
curve for the active deposit was plotted from the results, so that the 
ionization due to the 8 rays and to the y rays respectively, at the same 
instant, could be found by interpolation. The leaf with the active 
deposit was hung by a thread at 50 cm. from the centre of the electro- 
scope. When measuring the y ray ionization, the 8 rays were partly 
absorbed by a zine cylinder around the leaf, partly deflected by a 
powerful magnetic field. The electromagnet and cylinder were removed 
when the 8 ray ionization was measured. 
At atime when the radium B present was 57 per cent. of the radium 
C, the B rays gave 11-7 divisions/minute, and the y rays 0-3. Hence, 
taking u — -0033, and u — -019 for the two cases 
X /1-17 + +57 x/2-56=11-7 
.. X== 10-9, the number of divisions a minute due to radium C alone, 
corrected for absorption, whence 
i / Ki = 10:9/0-3 — 36. 
Again, when radium B was 29 per cent. of radium C in quantity, 
the 8 rays caused 7-5, and the y rays -24 divisions/min. so that x/1-17 
+ «29 x/2-56— 7-5 
and x—#7-8. Hence K/K’ = 7-8/ -24—33. 
See. IT, 1911..°6. 
