( 458 ) 



which appears to me less suitable, to surv^ey the connection of the 

 phase-equilibria. The representation now worked out by Smits (see 

 his communicaiion fig. 4) is a p , .^-projection of ray own spacial 

 figure with p ,t , x as coordinates which, however, had not yet been 

 published. 



This representation is well suited to explain at once which are 

 the transformations which take place on the different parts of the 

 three-phase line, owing to change in pressure or temperature, and 

 finally lead to the disappearance of one of the three phases. 



Those transformations are dominated first of all by the connection 

 of the compositions of the three-phases. 



From the figure it will be seen at once that, if we indicate the 

 solid compound by S, the coexisting liquid by L, and the vapour by 

 G, the order of the compositions of the phases commencing with 

 one richest in the volatile component A, is as follows : 

 on branch CTRF : GLS 



,, ,, FijT : G-)oL/ 



,, ,, 6rX/ : ourxy. 



The only transformation which can take place between three 

 phases is such that one is converted into two others, or reversely. 

 That one must then necessarily be the middlemost in composition, 

 consequently successively L, S, G. 



The most rational division of the three-phase line is obtained when 

 this takes place according to the transformation which occurs between 

 the phases, and we will, therefore, call in future the branches on 

 which L, S or G are the middle-bodies, the branches 1, 2, 3. 



The transformation of 1 into 2, therefore, takes place in the point 

 F where S=L, that of 2 into 3 in the point G where >S=: G. 



If now we observe in what direction that transformation takes 

 place, for instance on applying heat, we have 

 on branch 2 : S —^ G -\- L 

 J, ,, o : o — p -L/ — > ix 



on the other hand on branch 1 we have : 



on the part TRF -. S -\- G -^ L branch la 



„ „ „ CT : L^S+G „ lb 



whilst in the point T itself, both transformations are without heat 



effect. The reversal of the direction of the transformation causes 



retrograde phenomena, on increasing or lowering the temperature. 



A reversal of the direction of the transformation caused by a 

 change in pressure also takes place on either side of the point F 

 on branch 1, or on branch 2 if the compound melts with contraction, 



