282 



On the Spontaneous lonisation of Gases. 



gases was published by Matteueci* in 1850. He found the loss to be 

 the same in air, carbonic acid, and hydrogen. Warburg,t in 1872, 

 found the loss in air and carbonic acid to be equal, and in hydrogen 

 about half as great. They used much larger vessels, and it is 

 probable that in Warburg's experiments the saturation current was 

 not approached, so that the leakage was not even approximately pro- 

 portional to the ionisation ; it is perhaps in this way that the discre- 



Relative Conductivity (Air =1). 



paricy is to be explained. In Matteucci's experiments, however, the 

 leakage was independent of the potential ; he was therefore using 

 potentials high enough to produce the saturation current, and some 

 other explanation is in this case required. One possible way out of 

 the difficulty would be to suppose that the ionisation ig to be explained 

 by a slight radio-activity of the walls, the radiation being of only 

 moderate penetrating power. In a large vessel all the radiation might 

 be absorbed even by hydrogen, and in that case we should expect to 

 find the same total number of ions produced in a given time whatever 

 gas the vessel contained.! At the same time the similarity between 

 the results obtained for the relative ionisations of different gases in the 

 small vessel with those of the same gases exposed to the action of 

 radium would be explained (the ionisation being due to a similar 

 cause), as also would the departure at the higher pressures from the 

 simple law connecting pressure and rate of leak, which holds for the 

 lower pressures, for at the higher pressures the intensity of the rays 

 might be considerably reduced by absorption before reaching the 

 central portions of the vessel. 



Until, however, further experiments have been made it would, I 

 think, be premature to conclude that the ionisation is due to radiation 

 from the walls of the vessel. 



* ' Annales de Chimie et de Physique,' vol. 28, pp. 385-429. 

 t ' Annalen d. Physik u. Chemie,' vol. 145, pp. 578-599. 



J As in gases exposed to uranium rajs in a large veisel (Rutherford, ' Phil. Mag.,' 

 vol. 47, p. 136, 1899). 



