194 



Messrs. J. P. Kuenen and W. G. Robson on 



The former result was therefore due to the proportion of 

 alcohol being too large. In order to ascertain whether a 

 lower critical temperature for the two liquids existed we 

 cooled some methyl alcohol to — 78° 0. in solid carbonic acid, 

 and distilled some ethane into it. The two layers appeared 

 again quite distinctly, without any indication of a critical 

 point. 



The pressures of the three phases (Table IV.) will be seen to 

 be smaller than those for pure ethane. The pressures indi- 

 cated by pb are those registered when the last trace of vapour 

 was just disappearing. That these are somewhat higher than 

 the pressures read at a larger volume is due to the slight 

 impurity in the ethane (see Table I.). From the theory it 

 follows that if the pressure of the three phases is between the 

 vapour-pressures of the pure components, and no maximum 

 vapour-pressure exists, then the composition of the vapour is 

 not between but outside the compositions of the two liquids. 



Fig. 6. 



Ethane. Alcohol. 



v- 



Fig. 6 shows diagrammatically the relative position of the 

 three points (a, b, c) representing the three coexisting phases 

 in the v-x diagram in this case. The dotted curves are the 

 plait-point curves of the two halves of the vapour-liquid plait 

 and the liquid plait. The straight lines connect the co- 

 existing phases, and show by their position in which direction 



