DISCHARGE OF ELECTRICITY FROM HOT PLATINUM. 
2B‘) 
Temperauire. 
Current per 
square centimetre. 
° 0 . 
amperes. 
1516 
127 xlO-s 
1457 
70 X 10-8 
1400 
20-4x 10-8 
134.3 
5-Ox 10-8 
1287 
1 - 6 x 10-8 
These numbers give Q = 120,000. 
The variation of the negative leak with the temperature, using 40 volts, was also 
measured at a pressure of 133 millims. The following talde gives the results :—■ 
Temperature. 
Current per scpiare 
centimetre. 
° 0 . 
amperes. 
1310 
192 X10-8 
1187 
33-4 X10-8 
1069 
5-66 X10-8 
961 
l-04x 10-8 
These numbers give Q = 36,000. The leak in air or in a vacuum, using a wire 
well cleaned with HNOg, at 1310° C. is only about 2 X 10ampere per square 
centimetre. 
The following table gives the values of Q found at the different pressures, and also 
the approximate values of the constant A in the formula x = :— 
Pressure of hydrogen. 
Q. 
A. 
millims. 
0 (wire cleaned Avith 
155,000 
6 X 108 
HNO 3 for 24 hours') 
0 (wire cleaned with 
131,100 
6-9 X 10' 
HNO 3 for one hour) 
0-0013 
120,000 
10 ' 
0-112 
85,900 
5-3X10^ 
133-0 
36,000 
O'l 
Thus the presence of hydrogen diminishes the amount of energy required in the 
production of the negative ions and consequently greatly increases the leak. It 
seems very probable from the above results that the action of the hydrogen depends 
on its absorption by the platinum, for the leak obtained depends apparently on the 
amount of gas absorbed by the wire and only indirectly on the gas pressure in the 
apparatus. The leak, when there is equilibrium between the wire and gas, is nearly 
proportional to the pressure at low pressures, but increases less quickly than the 
