Maximum or Minimum Vapour-Pressure. 131 



\ , and during the transformation part of its carbon dioxide 

 will thus be condensed into solid. The evaporation requires 

 heat, but the formation of solid yields heat. As the difference 



Fig-. 5. 



V-. 



in composition between liquid and vapour increases, the heat 

 of solidification also increases, and at the two have become 

 equal. Beyond up to T the heat developed is larger than 

 the heat absorbed, and H becomes negative. 



Fisr. 6. 



The following gives an answer to the question, on what 

 conditions the sign of the heat of transformation at and near 

 the triple point depends. If x x and x 2 are the amounts of 

 ethane contained in a gramme of the liquid and the vapour 

 respectively the evaporation of one gramme of the liquid 



K2 



