696 Research Staff of the Gr. E. C. London, on the 



As in other gases, no evidence could be obtained that a 

 discharge through phosphorus vapour under a potential less 

 than the glow potential would cause any disappearance of 

 the vapour, even if the (/, Y) characteristic indicated con- 

 siderable ionization. 



21. The disappearance of gases in the presence of phos- 

 phorus. — For this investigation the lamp was filled with the 

 gas in question to a known pressure ; tap B was then closed, 

 A opened, and sufficient time allowed lor the phosphorus 

 vapour to attain by diffusion its equilibrium vapour-pressure 

 throughout the lamp. The filament was then heated, and 

 ■the potential V raised till the, glow discbarge occurred. The 

 glow potential was never higher than that of the phosphorus 

 vapour ; if there was much gas present it was less. The 

 presence of phosphorus did not seem to alter considerably 

 the current passing in the glow discharge; since this current 

 represents the' saturated thermionic current, the thermionic 

 emission was unaltered. 



The gas disappeared initially in the discharge much more 

 rapidly than if phosphorus were not present, except possibly 

 if the gas were argon. If the gas were hydrogen, the gas 

 would not disappear completely unless the initial pressure 

 of the gas were below a certain limit (about 0*04 mm. in the 

 lamp of fig. 1). If it were GO or nitrogen, it would disappear 

 however great the initial pressure*; in nitrogen the dis- 

 appearance was accompanied as before by a rapid blackening 

 of the walls and wastage of the filament. In argon, so far 

 as could be ascertained, the presence of the phosphorus made 

 little difference, but the disappearance of this gas is so slow 

 and irregular that it is difficult to decide anything definitely 

 about it. Mercury could not be examined, because the 

 metal acts directly with the vapour, and one or other 

 disappears completely without any discharge at all. 



If, instead of a definite charge of phosphorus vapour being 

 mixed with the gas initially, the tap A were left open so 

 that a continual supply of the vapour was provided, then the 

 disappearance continued rapidly with hydrogen, nitrogen, 

 and GO as long as the discharge lasted and fresh gas was 

 supplied; now the amount of hydrogen that could be made 

 to disappear was, like that of the other two gases, unlimited. 



* This statement is not strictly true. If the initial pressure is too 

 high, greater than Olo mm., the disappearance of gas begins almost 

 indefinitely slowly. But if, while the pressure of the gas is always kept 

 below (say) OOo mm., fresh, gas is admitted as the disappearance 

 proceeds, the amount of CO and nitrogen that can be made to disappear 

 seems almost unlimited. 



