L 247 ] 
YL The Effect of Hydrogen on the Discharge of Negative Electricity 
from Hot Platinum. 
By Professor H, A. Wilson, F.R.S., Kings College , London. 
Received January 23, —-Read February 13, 1908. 
The effect of hydrogen on the discharge of negative electricity from hot platinum was 
examined by the writer in 1903 (‘Phil. Trans.,’ A, 352, vol. 202, 1903); it was 
found to produce a very large increase in the current carried by the discharge. At 
pressures below 0T millim, of mercury the leak was found to increase' with the 
pressure and to fall when the pressure was reduced. The experiments in the paper 
just referred to were all done with nearly new platinum wires which had not been 
heated in the gas for any great length of time, because it was known that long continued 
heating caused the wire to disintegrate, its surface becoming covered with a network 
of cracks. The present paper contains an account of a series of experiments in which 
wires were heated for long periods in hydrogen, so that any gradual changes in the 
effect of the hydrogen could be observed. It appears that continued heating in 
hydrogen alters the character of the effects observed, so that the behaviour of an old 
wire may be very different from that of a new one. 
In the previous paper I suggested that the effect of hydrogen was due to the 
presence of hydrogen in the surface layer of the platinum, and this view appeared to 
be supported by the facts. Professor O. W. Richardson (‘Phil. Trans.,’ A, 413, 
vol.-207, 1906) puts forward a different theory, viz., that the hydrogen alters the 
state of the platinum, so that the effect may remain even after the removal of all the 
hydrogen. 
If the wire is heated in oxygen the large leak always immediately disappears, so 
Professor Richardson supposes that the oxygen destroys the change in the state of 
the platinum produced by the hydrogen. According to the other view the oxygen 
burns up the hydrogen present at the surface of the platinum. 
The very large increase in the negative leak produced by hydrogen has been 
recently confirmed by several observers, including O. W. Richardson (loc. cit.), 
F. Horton* and G. H. Martyn. f 
Measurements of the current at different temperatures enable the energy required 
VOL. CCVIII.-A 432. 
* ‘Phil. Trans.,’ A, 416, 1907. 
f ‘ Phil. Mag.,’ August, 1907. 
26.5.08 
