390 



should however be kept in mind that in tlie immediate vicinity of 

 the maximum point of sublimation only the reactions a, h and c 

 can take place (compare the reaction series A^^, B^ and C.). Reaction 

 d can take place at a greater distance from this point only. 



We maj also consider the different cases from yet another point 

 of view. For this purpose we lake two saturation curves and their 

 corresponding vapour saturation curves. We let these intersect one 

 another in such a way, that the two liquid points of intersection 

 as well as the two vapour points of intersection are situated in 

 opposition with respect to the line FF' . 



If we consider stable conditions only, merely a part of each curve 

 will remain. We may now distinguish several cases, according as 

 the points of maximum and minimum pressure are situated on the 

 stable or metastable parts of these curves, and these will be in 

 agreement with what has been said above. It is evident that for 

 each stable or metastable point of maximum or minimum pressure 

 on a saturation curve there exists a stable or metastable point on 

 the corresponding vapour saturation curve. 



In fig. 2 the points of maximum pressure are indicated by x and 

 x', the points of minimum pressure on the saturation curves by y 

 and y'. The two curves intersect each other in fig. 2 in such a way 

 that these four points are stable, consequently the corresponding four 

 points (not drawn in the figure) on the vapour saturation curves 

 are also stable. 



II. The temperature is equal to the maximum point of sublima- 

 tion Tj) . 



The two liquid points of intersection are situated in opposition 

 with respect to the line FF' ; one of the vapour points of inter- 

 section is situated on the line FF' . We imagine in fig. 2 or 3 the 

 point gi on the line FF' . When a congruent sublimation takes place, 

 ^1 is situated between the other two points, with an incongruent 

 sublimation F or F' is situated there. 



III. The temperature is higher than the 

 maximum point of sublimation Td , but 

 lower than the minimum melting point Ts . 

 The two liquid points of intersection are 

 situated in opposition with respect to the 

 line FF' ; the two vapour points of inter- 

 section are situated in conjunction with 

 respect to that line. One of the maiiy dia- 

 grams satisfying these conditions is drawn 

 Fig. 3. in fig.^3. In the equilibrium i^-[-^'+^''Q"id^ 



