200 



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



For instance (Table IX.), at 38°*82 C. the two liquids 

 become identical and mix at a pressure of 53*14 atmospheres, 

 while the three-phase pressure (measured at the moment of 

 the disappearance of the vapour) is 53*07 atmospheres. The 

 pressure over and above the three-phase pressure required for 

 the mixing is only *07 of an atmosphere. At the critical 

 temperature itself (38°* 6 7) no pressure would be required 

 at all. As the temperature rises the excess of pressure required 

 increases. At 40°*55 the three-phase pressure is 54*75 atmo- 

 spheres (as calculated from Table VIII.), while the plait-point 

 pressure on the liquid plait is 55*70 atmospheres, i. e. almost 

 an atmosphere more. These examples show sufficiently that 

 the excess of pressure required is small at temperatures only 

 slightly above 38°*67 C. 



The first mixture (Table VIII.) contained so little alcohol 

 that at no temperature could critical phenomena of the liquids 

 be observed, the lower liquid layer disappearing before the 

 plait-point was reached. The pressures at which this happens 

 are lower than the pressures at which the second mixture 

 shows plait-point phenomena as they should be. 



Just above the critical point for this mixture (and the 

 same holds for the other alcohols) the influence of pressure is 

 very marked indeed, and the same thing may be true for 

 many other mixtures in the neighbourhood of a critical point 

 for two liquids. 



The tables for butyl alcohol do not require any further 

 explanation, the phenomena being very much the same as 

 for propyl alcohol. 



Table X. — Ethane and Butyl Alcohol (I.). 



t. 



V- 





14-95 



32-86 



1 



22-9 



38-88 





3195 



3335 



46-66 

 48-04 



1 Vapour disappears by com- 

 [ pression ; two phases. 



4123 



56-55 





5015 



6849 



J 



