
Heating Effect of the Radium Emanation. 2LT 
first certain observation of the heating effect of the radium in 
the emanation-tube could not be made until about 10 minutes 
after removal of the emanation. It is essential to allow an 
interval of at least 5 minutes in order to allow the glass 
envelope to take up the temperature corresponding to the 
source of heat inside it. 
On account of the rapid initial change in emanation X, we 
can only conclude from the experiments that about 41 per 
cent. of the total heating effect of radium is due to the 
emanation together with the first change in emanation X. 
The other results all indicate that the heating effects accompany 
the emission of a rays; for example, the minimum heating 
effect due to de-emanated radium is 25 per cent. of the total, 
and the activity is also 25 per cent. of the total activity, and 
consists entirely of 2 rays. Both the radiation from the 
emanation and that from the first change in emanation X 
consist entirely of a rays; and there can be little doubt that 
the emanation does give rise to a heating effect of the same 
order of magnitude as is observed in the other changes, 
which are accompanied by a rays. Further experiments are, 
however, in progress to separate, if possible, the heating effect 
of the emanation from that due to the first change in emana- 
tion X. 
The decrease of the heating effect due to the excited 
activity after the first sudden drop is not very rapid at first, 
and, in this respect, closely resembles the decay of the excited 
activity. It thus appears probable that the second change 
in emanation X, which does not give rise tu a rays, is also 
not accompanied by the same emission of heat as in the 
other changes. Further experiments are in progress to settle 
this point. 
The rate of heat emission of radium, when in a state of 
radioactive equilibrium, is thus made up as follows :— 
Percentage Percentage 
: 2 Nature of propor tion of proportion of 
meme products. rays. activity measured total heating 
by a rays. effect. 
Radium 
(freed from a rays. 25 25 
active products). 
| 
ae 
Emanation. a rays. 18 
1 
Y 2 
Emanation X ae Pitre st 
(first change). reer 15 
! 
y 
Second change. No a rays. 0} 
I 
y 42 - 6 a 6 34 
Third change. a, 8, & y rays. 42 
