: | Ty aN 
THE 
LONDON, EDINBURGH, ann DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[SIXTH anata | 
’ Bs 
eR Te hs 
JULY 1904. ts 
m5 hi 
VO « 
\ : 
I. The Diffusion of Hydrogen through Hot Platinum. ~, 
By O. W. Ricwarpson, J. Nicon, and T\ PARNELL *. / 
of tee fact that platinum is permeable to, and. capable “of 
absorbing, hydrogen was first observed by Graham, 
and has since then been investigated by a number of scientists. 
Recently, A. Winkelmann + (who also made experiments with 
palladium {) has carefully measured the rate at which 
hydrogen under different pressures diffuses through thin- 
walled platinum tubes which are heated and exposed to the 
atmosphere externally. These experiments show that the rate 
at which the hydrogen diffuses through the platinum is not 
proportional to the pressure, as one might naturally have 
expected it to be, but is very nearly proportional to the 
square root of the pressure. Winkelmann shows that this 
result can be explained by supposing the hydrogen to dis- 
sociate into atoms which are capable of diffusing through the 
platinum, whilst the undissociated hydrogen is not. 
As there is no other evidence, so far as the authors are 
aware, that free hydrogen dissociates at high temperatures, 
it seemed worth trying whether this conclusion would be 
borne out by further experiments, or whether the facts might 
not be explained equally satisfactorily on some other hypo- 
thesis. With this object in view, the authors set out to 
examine the variation of the rate of diffusion of hydrogen 
through hot platinum with the driving-pressure and the 
* Communicated by Prof. J. J. Thomson, F.R.S. 
+ Drude’s Ann. vol. viii. p. 388. 
{ Loe. cit. vol. vi. p. 104. | 
Phil. Mag. . 6. Vol. 8. No. 43. July 1904. B 
