504. Mr. FE. F. Burton on a Radioactive 
had once been well boiled, the gas expelled on any subsequent 
re-boiling was not appreciably radioactive. In the present 
investigation air was drawn through a selected sample of oil 
into the cylinder on three consecutive days, and again on the 
sixth day, the first measurement being made about 24 hours 
after the petroleum had been pumped from the well. Hach 
time the oil was used the bath was brought up to the boiling- 
point and the air bubbled through it for 15 minutes, when 
observations on the conductivity of the air in the cylinder 
were commenced and continued at intervals over a period of 
about 20 hours. 
TABLE LV. 
Curve 1. | Curve 2. Curve 3. | Curve 4. 
| , |Current. ‘ |Current. ||»: ' Current. ; Current: 
Time. | arb Sc.| ~i™e- | Arb. Se.| Ti™e- | Arb. Sc.|| T™Me | Arb, Se. 
hie han bh om he om ) Jae) oe 
0 10| 1587 || 0 30] s00 || 0 40] 49 0 35| 298 
O.30| 1742 | 1.0! 834 | 83 101, 58 I vO. 5a eee 
1 5 | 67 | 1.30) 872 13 0} 48 Ss toe 
i 30| 2037 || 3 40| 926 || 24 © | 41 |) 22 o| 25-2 
1 50| 2142 | 5 O|} 920 | | 
2 30| 2225 || 18 O 84:3. || 
3 30] 2260 | | | | | 
4 0} 2242 | | | / 
8 15} 2111 | | | . 
22 0}! 1760 || | | 
| | 
The results which are embodied in Table IV., and illus- 
trated by the curves in fig. 3, show that the activity acquired 
by fresh air, when drawn through the oil, gradually decreased 
from day to day. The curves corresponding to the different 
tests exhibit the same characteristics as that in fig. 2. In 
each case the conductivity rose to a maximum in about 
three hours, and then gradually decreased. The maximum 
currents in the four trials were respectively 13°9, 5°6,3°2, and 
1-9 times the conductivity of the ordinary air, thus showing 
that the oil at the end of a week still possessed in a’ marked 
degree the power to impart radioactivity to air drawn through 
it. Experiments made with a sample of oil, which had been 
used in some preliminary tests and had been placed aside in 
a tightly-corked glass vessel, for over a month, gave values 
almost identical with those represented by curve 4, fig. 3, 
the maximum conductivity impressed in this case being 1°6 
times that of the normal air. From these results it would 
