\ Om ee 
298 RADIO-ACTIVE PROCESSES [CH. 
once into emanation X. The initial change of emanation X— 
about half changed in 55 minutes—will also be disregarded for 
the same reason. 
Let A, and A, be the constants of decay of activity of Th X 
and emanation X respectively. Since the activity of Th X and 
of emanation X falls to half value im 4 days and 11 hours respec- 
tively, the value of A, =°0072 and of X,='063 where 1 hour is 
taken as the unit of time. 
It has already been shown (section 175) that after a time ¢ 
the activity J;, of a product in which there is a secondary change, 
is given by 
= = Gow € + 
0 
eke Hos 
No cee Ay Ne at Dri 

e-ts-nt) ; 
where J, is the intensity of the radiation immediately after separa- 
tion and K the ratio of the ionization produced in the secondary 
change to that produced in the primary change. By comparison 
of this equation with the curve of variation of the activity of Th X 
with time shown in Fig. 57, Curve A, it is found that the value 
of K is about *44. 
, Ll a 
The calculated values of 7 for different values of ¢ are shown 
0 
in the second column of the following table, and the observed values 
in the third column. 


Ti Theoretical Observed 
TNS value value 
O 1:00 1:00 
"25 days 1:09 — 
‘Ol eee 116 
I a 1191 bs} HLOLL7/ 
1k5 55 AA 
2 rd 1:04 == 
3 a “875 88 
4 r 15 72. 
6 35 53 DS 
9 % 315 295 
te 5 15S7/ “sy 




The theoretical and observed values thus agree within the 
limit of error in the measurements. The theoretical curve is 
