851 



Under pressures lower than Pj}, the boiling point curve cojisists 

 therefore of one single branch with the one extremity on CQ and 

 the other on AQ' ; on this curve either a point of maximum (fig. 6) 

 or a point of minimum temperature (fig. 5) occurs or neither of 

 these points (fig. 4). 



Under the pressure Pb now also the point B itself occurs, Pyjis 

 viz, the pressure of the minimum melting point or in this case as 

 B is one of the components, therefore also the pressure in the 

 triplepoint of the substance B ; under this pressure exists the unary 

 equilibrium solid B -\- liquid B -\- vapour B. Consequently the 

 boilingpointcurve of the pressure Pb consists of a branch with 



Fig. 6. 



