603 



At first let us contemplate fig. 5. The arrows indicate the direction 

 in which the pressure increases, therefore, it is assumed that on 

 these curves neither a point of maximum- nor a point of minimum- 

 pressure occurs. When this however is the case, these points form the 

 limit-curve, former!}' treated, wliich is easy to draw in the figure. 



The saturationcurves disappear at Tfj in the point H; the corre- 

 sponding vapourcurves disappear at tiie same time in the point H^, 

 which is not drawn. We see from fig. 5 that Tn is the highest 

 temperature at which, in the binary system BC, the equilibrium 

 F -{- L -\- (t can still occur. In this case 7// is also the highest 

 temperature at which in the ternary system the equilibrium F -\- L -\- G 

 can still occur. 



In fig. 6 the saturationcurve of the temperature Th does not 

 disappear in the point H; it forms a closed curve, which touches 

 the side of the triangle in a point H. On further increase of tem- 

 perature it comes completely within the triangle and disappears in 

 a point R. It is evident that these closed curves, and also the not- 

 closed curves, being situated in the vicinity, show a point of maximum- 

 and a point of minimumpressure. In this case, therefore, a limit-curve 

 exists, going through the point R. The curves situated at a greater 

 distance, need not necessarily show this point of maximum and that 

 of minimumpressure. 



If it is imagined viz. that these points, on extension of the 

 curves, continue to approach closer to the side BC and that they 

 coincide with this at last ; the point of maximumpressure disappears 

 somewhere between 7/ and C, the point of minimumpressure between 

 II and B on the side BC. The limit-curve then terminates in both 

 these points. 



Also we see from the figure that the highest temperature {Tn) 

 at which in the ternary system the equilibrium F -\- L -\- G may 

 still occur, is higher tlian Th- 



In figs. 5 and 6 the curves of diiferent temperatures are all drawn 

 in a same plane. Imagining however perpendicular to this plane a 

 temperature axis and the curves to be drawn in space according to 

 their temperature, the saturationsurface of F under its own vapour- 

 pressure arises. In a similar way the corresponding vapoursurface 

 arises. 



In the surfaces belonging to fig. 5 the highest points (ƒ/ and H^) 

 are situated on the side-plane BCT; in the surfaces belonging to 

 fig. 6 the highest points {R and ZtJ are situated within the prism 

 and not on the sideplane BCT. 



