Disappearance of Gas in the Electric Discharge. 935 



by a layer of salt, whatever, its chemical nature. Further, 

 the phosphorus curve rises to the step with increase in 

 amount of phosphorus nearly as steeply as the amount 

 absorbed by salt ; in fact, we have never been able to satisfy 

 ourselves that there can be absorbed by phosphorus an 

 amount of gas intermediate between that which can be 

 absorbed by plain glass and that corresponding to the 

 step. (The difficulty of deciding the matter is that, if 

 neither salt nor phosphorus is present, the absorption is 

 not determinate, but represents an equilibrium between 

 absorption and liberation by decomposition of the glass under 

 bombardment.) It is not at all clear why the increase in 

 absorption up to the step caused, by salt or phosphorus is 

 discontinuous; for, according to the theory proposed, it 

 might be expected that quantities of material insufficient to 

 cover the walls completely would cover them partially and 

 so give an intermediate absorption. It is possible that, if the 

 walls are not completely covered, absorption is again masked 

 by liberation of the gas from the glass ; but the difficulty, 

 whatever its explanation, is the same for phosphorus as for 

 salt. The increase of absorption with quantities of phos- 

 phorus greater than that required for the step, which is not 

 shown by salt, will concern us presently. 



The quantity of gas absorbed at the step is not very 

 different from that corresponding to a monomolecular layer. 

 The calculated amount is *0016 mgm. (or '0008 if the layer 

 is monatomic), the observed *0023. The discrepancy is 

 explicable if the molecules present to the surface a diameter 

 less than that estimated by the usual methods, or, in other 

 words, if the molecules are attached " end-on/' The view 

 that molecular layers are concerned would explain the close 

 similarity between the volumes of nitrogen and hydrogen 

 absorbed in similar circumstances. 



19. If this general view is correct, it is natural to inquire 

 in which direction the polar layer is directed and ions o£ 

 which sign enter into combination with it. The very small 

 absorption of the inactive gases, which do not form negative 

 ions, suggests that it is negative ions which are absorbed by 

 the layer. We have not been able to devise an experiment to 

 test this point, but there is some indication from another 

 source that layers of salt, deposited as we have described, 

 are able to bind negative charges. For Hamburger and his 

 associates have shown * that layers of salt so deposited have 



* L. Hamburger, G. Hoist, D. Lely, E. Oosterhuis, K. Akad. 

 Amsterdam Proc^ Sept. 21, p. 1078 (1919). 



