Tension and Complex Molecules. 385 



this paper, even admitting the sharp passage from the liquid 

 to the gaseous state, the constancy of this ratio cannot occur, 

 for, as we have seen, 



1 = ^, 



in which p is not constant, but in all cases is a function of 

 the temperature. 



We shall see later that systems consisting of two liquids 

 in contact (liquids with limited mutual solubility) can throw 

 some light on the nature of the liquids and we shall discuss 

 their properties a little more completely. 



§ 2. Some Properties of Two Superposed Liquids. 



Considering liquid systems with limited solubility we 

 have difficulties in explaining some laws governing that 

 phenomenon and in understanding how the two layers can 

 coexist without having the tendency to mix complete^. It 

 can be shown for example in certain cases (near the critical 

 point of dissolution), that we can have two liquids of very 

 different concentrations, but equal (within the limits of 

 experimental error) as regards surface tension *. Two layers 

 obtained when the liquid is disturbed correspond to this con- 

 dition if the critical point is gently departed from. Two 

 liquid layers have, according to KonovalofT t, an equal 

 vapour tension as well as the same vapour composition, 

 while their own composition is very different. If certain 

 properties of a solution remain the same, even with change 

 of concentration (for example, surface tension and vapour 

 tension), we can suggest, as an explanation, the hypothesis 

 that at the surface of a solution the concentration of the dis- 

 solved body is different from that in the interior. If, in 

 general, it be admitted that such a change of concentration 

 can occur in the surface layer, the formation of two solu- 

 tions of different concentrations but identical surface tensions 

 becomes admissible, and it is only necessary to suppose 

 equality in the surface concentrations. 



Such an interpretation is necessitated otherwise, in that 

 there exists a theory according to which the surface concen- 

 tration of solutions must differ from that of the deeper layers. 



* G. N. Antonoff, J. Ch. Phys. v. p. 372 (1907). 



t D. Konovaloff, Wied. Ann. xiv. (1881). See also Nernst, Theor. 

 Chemie, p. 525 (1913). 



