in Gases at Low Pressures. $0o 



the metals used, and was probably the atom of sodium. 

 The spectroscopic work of Horton * points to carboti 

 monoxide as the carrier, while Garrett f, from measurements 

 of e/m } finds positive particles as small as the hydrogen 

 atom. 



In some experiments on the positive leak in different 

 gases, Horton J has found that carbon monoxide has a great 

 affinity for the positive electricity from a heated phosphate, 

 so that when carbon monoxide is present in a gas the positive 

 leak is practically wholly carried by the carbon-monoxide 

 molecules. 



It is well known that the carbon-monoxide spectrum is 

 invariably visible in a discharge-tube. Heating the tube or 

 prolonging the time of discharge makes the spectrum more 

 pronounced. In his experiments on the variation of the 

 positive leak from metals with the pressure, Richardson § 

 found that heating the walls of his tube with a Bunsen 

 burner enormously increased the leak. In one instance 

 where the pressure before heating was O0005 mm., heating 

 for a few minutes increased the leak from 2*2 x 10~ 13 amp. 

 to 5x10"° amp., i.e., 20,000 times, while the gas from the 

 walls only sent up the pressure to 0'001 mm. He men- 

 tioned that this did not depend on the cleanliness of the 

 tube. Exactly the same effects were produced after the 

 tube had been boiled several times in pure nitric acid and 

 rinsed out many times in distilled water. When the walls 

 were kept cool by a water-bath no such effect was noticed. 

 This emission of carbon monoxide from the walls of a glass 

 tube when heated, or during a discharge, probably accounts 

 for Horton's result with the spectroscope. 



As regards the mechanism at the surface of the platinum 

 and the phosphate which produces the positive electrification 

 nothing is known. Wilson || points out in a paper recently 

 published that aluminium phosphate gives no positive leak 

 when heated on a Nernst filament, so that the platinum must 

 play an important role in the ionization of the gases present. 

 He attributes the increase in the positive leak produced by 

 moisture to the reaction of traces of carbon in the platinum 

 with the water-vapour giving rise to carbon monoxide and 

 hydrogen which readily carry away the positive electricity. 



The evidence seems to show that if carbon monoxide 



* Proc. Roy. Soc. A. lxxxiv. 1910. 

 t Phil. Mag. xx. p. 582 (1910). 

 X Proc. Camb. Phil. Soc. xvi. p. 89. 

 § Phil. Trans. A. ccvii. p. 19. 

 jl Phil. Mag-, xxi. p. 631 (1911). 



