SURFACES OF DISCONTINUITY 



563 



drop surface. Suppose that saturation in adsorption were 

 attained when the surface is at its maximum value, then when a 

 subsequent contraction takes place the compression (in two 

 dimensions) thereby produced might cause some of the adsorbed 

 material to gather into droplets on the surface, and so more of it 

 would accumulate on the surface than would correspond to true 

 adsorption. Be that as it may, the general nature of McBain's 

 results may be indicated broadly thus : 



Firstly, the calculated value of r tends to a maximum as the 

 bulk concentration increases. Actually this might be antic- 

 ipated from the equation of Szyszkowski quoted earlier. Thus 

 according to it 



(To — cr 



= 6 log 



(-3 



and 



hero 

 T = -^ 



Rt c + a 



which approaches a limit hao/Rt as c increases. 



Secondly, the observed values of T also rise to a maxi- 

 mum, but during the whole course of events are definitely greater 

 than r calculated. The table for p-toluidine shows this. 



The results for camphor show also a discrepancy of about 

 two to one; while for amyl alcohol the discrepancy is still greater, 

 amounting to about four or five to one. 



At first McBain regarded this discrepancy as due, in part at 



