848 



S=-^ and S^ = ~—- 

 ,i' + y '^i + 2/i 



Siibslituling from this the values of y and i/^, in (5), we find 

 1 /JP\ _ 1 ^1 /" 'S 



jurI ; .... (7) 



1 





RT' 



As *S and ^S', are very small we have equated, (J — »S'j) : (1 — aS) = J. 

 When the binary equilibrium B -[- L -\- (t is situated on the side 

 BA {i/=0) we tind from (6) 



RT- \dy)y=o AF, ' y\ S, 

 and v. . . . (8) 



' ('^\ 



■f(-I) 



Rr \dy Jy^Q WL, 



We see that (7) and (8) are in accordance with (14) and (15) (XI); 

 we may deduce from this for the addition of a new substance to 

 the binary equilibrium B -\- L -\- G the same rules as was done in 

 communication XI for the equilibrium F -\- L -{- G. It is however 

 to be considered with this that now ;S and *S'i are positive. We see 

 that the position of the threephase triangles in fig. 2 is in accordance 

 with these rules. 



In communication XII we have deduced in different ways form 

 and position of the saturationcurves under their own vapourpressure 

 in the vicinity of the point of maximum temperature and of the 

 boilingpoinfc curves in the vicinity of the point of maximum pressure 

 of the binary equilibrium F -\- L -\- G. 



All this applies also when the solid substance is one of the com- 

 ponents. We must keep in mind that in the binary system B -^ L -\- G 

 there occurs not always a maximum of pressure and temperature, 

 w^iicli is indeed the case in the binary system i^-f- -^4" '^- For that 

 reason we shall express these rules now in the following way. 



Let in fig. 5 and 6 (XI) H be a point of maximum tempera- 

 ture of the binary equilibrium B -\- L -\- G. The saturationcurve 

 undpr its own vapourpressure of B disappears on increase of T in 

 H [fig. 5 (XI)], when the concentration of the new substance in the 

 liquid is greater than in the vapour; it does not disappear in H 

 [fig. 6 (XI)], when the concentration of the new substance is smaller 

 in the liquid than in the vapour. 



If we imagine in fig. 5 and 6 (XI) H to be replaced by the 



