700 Research Staff of the G. E. C, London, on the 



and within much the same limits as if there were no phos- 

 phorus present. The question arises whether any phosphiue 

 is restored. Langmuir found that his active hydrogen would 

 react with phosphorus to form phosphiue, and, in accordance 

 with the principle of § 11 that any chemical compound will 

 be formed to some extent that can be formed, some phosphine 

 is to be expected. It is very difficult to detect in the 

 presence of hydrogen, phosphorus vapour, and water ; the 

 only method seems to be to condense as much as possible 

 of the gases restored (i. e. P, H 2 0, PH 3 ) in liquid air, and 

 to note the increase of pressure as the temperature of the 

 cooled tube is allowed to rise. Phosphiue boils at 153° K. 

 Some observations made in this manner seemed to indicate 

 the presence of a small amount of gas which volatilized 

 between 120° and 180° K. ; siuce water does not volatilize 

 appreciably till 200° K., and phosphorus until still higher 

 temperatures, the gas may have been phosphine. But its 

 amount was variable and never more than 25 per cent, of 

 the restored hydrogen; accordingly, even if phosphine is 

 formed, its formation cannot be the main cause of the 

 increased amount of gas that will disappear. Moreover, 

 since phosphine is a gas, its formation will only result 

 directly in the reduction of the volume of hydrogen by one- 

 third. But since it is possible that umlimited quantities of 

 this gas, as of CO, can be absorbed in the discharge, its for- 

 mation might aid in the reduction of the hydrogen. 



If the gas that has disappeared is nitrogen, then no gas 

 is restored by baking the vessel *. But in this case the 

 yellow layer does not disappear on baking. This fact, 

 taken in conjunction with the marked blackening of the 

 walls, appears to us to suggest that the nitrogen and the 

 phosphorus are not liberated on baking, simply because they 

 are held to the w T alls by a layer of spluttered tungsten 

 deposited over them. When the general nature of the 

 results is considered, this appears to us a more plausible view 

 than that the nitrogen disappears by the formation of a 

 nitride. The loss in weight of the filament was always 

 decidedly less than that indicated by Langmuir's formula 



* More accurately, by baking it for 5 minutes, the .time sufficient to 

 restore all the CO and, in that case, remove all the yellow. If the vessel 

 is baked for some hours, the yellow disappears and possibly gas is 

 restored; but since it seems impossible by previous baking to exhaust 

 entirely the gas from the walls, the gas coming off may not be the 

 absorbed nitrogen. The previous baking in all cases had been so pro- 

 longed that the pressure would not rise by more than 0*0001 mm. during 

 o minutes' subsequent baking, unless gas had been absorbed in the 

 interval. 



