oo ee 
240 RADIO-ACTIVE EMANATIONS [CH. 
of the results obtained for a current of hydrogen of 1:38 cubic 
centimetres per second. 


ermmertare Divisions per second 
of the electrometer 
— 160° 0 
— 156° 0 | 
- 154°°3 1 
— 153°:8 21 
—152°°5 24 | 




The following table shows the results obtained for different 
currents of hydrogen and oxygen. 




Current of Gas T, 25 
Hydrogen ... 25 c.c. persec. | —1513 — 150 
1 BAe Bid x | —153-7 —151 
5 OZ. = —152 —151 
- eS Sie ‘ —154 — 153 
x S06 2°3 % 3 | —162°5 —162 
| Oxygen... BA seiee evince ytd eh elo oeD —151°5 
5 500 HS) | ig 0 — 155 — 153 





The temperature 7, in the above table gives the temperature 
of initial volatilization, 7, the temperature for which half of the 
condensed emanation had been released. For slow currents of | 
hydrogen and oxygen, the values of 7, and T, are in good agree- 
ment. Fora stream of gas as rapid as 2°3 cubic centimetres per 
second the value of 7, is much lower. Such a result is to be 
expected, for, in too rapid a stream, the gas is not cooled to the 
temperature of the spiral, and, in consequence, the inside surface 
of the spiral is above the mean temperature, and some of the 
emanation escapes at a temperature apparently much lower. In 
the case of oxygen, this effect appears for a gas stream of 0°58 cubic 
centimetres per second. 
In the experiments on the thorium emanation, a slightly dif- 
ferent method was necessary, on account of the rapid loss of its 
activity. The steady stream of gas was passed over the thorium 

