Tension and Complex Molecules. 387 



in order to explain the possibility of the existence o£ 

 solutions of various concentrations, bnt the same vapour 

 tensions, the equality of superficial concentration is not the 

 only possible hypothesis or condition. For it is quite con- 

 ceivable that near the critical point, the concentration of the 

 surface layers plays a certain role in the phenomenon of 

 equilibrium of two layers. Effectively if the two concen- 

 trations come to be equal for two different solutions, the 

 equality of vapour tension and of surface tension becomes 

 admissible. Nevertheless it is not possible by this hypo- 

 thesis to explain a whole series of properties of these 

 systems. 



In a departure from the critical point, the surface tensions, 

 as is known "*, commence to differ sensibly for the layers, 

 while the vapour tension remains in all cases the same for the 

 two layers. It is also known that the two superposed liquids 

 boil at an equal temperature and have the same freezing 

 temperature. These properties obviously cannot be accounted 

 for from the standpoint of the above theory. Evidently, in 

 order to explain these phenomena, it is necessary to take into 

 account the molecular state of the body dissolved in the 

 solution. 



A satisfactory hypothesis can be found, however, on the 

 basis of the following considerations exposed in the next 

 section. 



§ 3. Ihe Tension at the Interface of Two Liquids ivith 

 Limited Solubility in a State of Equilibrium. 



In the following we are going to call a 12 the interfacial 

 tension, a 1 and a 2 ^ ne surface tensions against the air of two 

 superposed layers in a state of equilibrium; we will call them 

 solutions 1 and 2. Thus ol x and « 2 are n °f tensions of separate 

 liquids but of the saturated solutions the two liquids form 

 when in equilibrium. 



The attempts to formulate a law connecting the surface 

 tension at the limit of the two liquids (a 12 ) with the tension 

 of the different phases (a 2 and a 2 ) have not up to the present 

 given any very satisfactory result. The theory of Eayleigh 

 has led to this result : 



Va 12 = V 'oe, 1 — V^a 2 , 



based on certain hypotheses regarding the layer of transition 

 which do not agree with the experiments. 



* See G. N. Antonoff, loc. cit. 



