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



6. The state of the walls has no effect within wide limits. 

 All kinds of: glass, cleaned or etched by any method or 

 coated with other substances by evaporation of solutions or 

 by chemical action, have the same absorptive power. On the 

 other hand, the absorptive power can be greatly increased by 

 " evaporating ; ' certain substances from an electrically 

 heated filament and so depositing them on the walls. The 

 ionization of the vapour is an important factor in this process. 

 Metallic tungsten is among the substances having this 

 property, but no relation has been found generally between 

 this property and others. These substances act to some 

 extent as substitutes for phosphorus. (Pars. 8-11.) 



The following subsidiary matters are dealt with : — 



7. In the absence of phosphorus or its substitutes, the 

 absorption is indeterminate, representing a balance between 

 true absorption and liberation. (Par. 12.) 



8. The absorption of gas mixed with phosphorus vapour 

 takes place in two stages — a very rapid absorption accom- 

 panying the deposition of the phosphorus on the walls, and a 

 slower absorption after it has been deposited. The same two 

 stages are characteristic of the substitutes considered in (6). 

 (Par. 13.) 



9. The occurrence of absorption seems determined simply 

 by ionization, and will occur, though very slowly, in the 

 absence of a visible glow. There appears to be no lower 

 limit to the pressure that can be attained by absorption in 

 the presence of phosphorus. (Par. 14.) 



10. The gas absorbed is liberated when the phosphorus is 

 evaporated from the walls ; that absorbed under the influence 

 of the substitutes of (6) cannot be liberated because the 

 substitutes cannot be evaporated. There is evidence of the 

 formation of such chemical compounds as PH 3 , but none of 

 the formation of compounds which are not formed in other 

 circumstances. The formation of these compounds is a 

 secondary and not a primary feature of the absorption. 

 (Par. 15.) 



11. Arsenic appears to have exactly the same properties 

 as phosphorus, as Whitney has found. Sulphur and iodine 

 were not examined. (Par. 16.) 



A general discussion of the results is undertaken, in which 

 the view is put forward that the absorption is determined by 

 the formation on the walls of the vessel of electrically polar 

 layers to which ions of the gas adhere in virtue of their 

 charge. It is probable that it is the negative ions that 

 adhere; if this is so, an explanation can be offered of some 



