8^ 



Curve qehfk in fig. 4 indicates 'the solution of the equilibrium 

 7f^ _|_ ^' _|_ /^ _|_ Q-^ wlien in a P, J'-diagram we draw the curve 

 7^_j_ I?' _|_ Q (consequently the curve of inversion F"^ F' -f- G) and 

 curve F -{- F' -\- L -\- G, then they coincide. 



In fig. 5 the line OFF' coincides with the side ^C' of tlie triangle ; 

 we assume viz. that the component B and its hydrate F occur as 

 solid substances; further we have also assumed that the component 

 A occurs as solid substance. The curves be, fg and //; are saturation- 

 curves under their own vapourpressure of A, ih and ef of B, ab 

 and <le of the hydrate F , the arrows indicate again the direction 

 in which the pressure increases. 



It is apparent from the figure that vz represents the solutions of 

 the equilibrium A -\- F -\- L -\- G, zw those oï A -\- B -\- L -{- G 



and zu those of B-\- F^L-\-G. 

 Consequently in z the invariant equili- 

 l)rium .1 + i>* + F ^ L -[- G occurs. 

 Curve zu terminates on side BC in 

 the quadrupiepoint u with the phases 

 B -\- F -\- L -\- G of the binary system 

 CB. When we remove the liquid Le 

 from the equilibrium B-\-F-\-he-\-G 

 occurring at the temperature T^. and 

 under the pressure Pe, we retain tlie mono- 

 variant binaiy equilibrium B-\-F-{-G. 

 When we draw in a 7^, 7^-diagram the 

 curve B-\-F-\-G (^therefore the curve of inv^ersion i~^B-\-G) and 

 curve B -\- F -{- L -\- G, these two curves coincide. We can say, 

 therefore : 



the vapourpressure of a solution, saturated with a component and 

 with its hydrate, is equal to the pressure of inversion of the hydrate 

 (the pressure of the reaction F^B-\- G). 



From the direction of the arrow on de it follows that the pressure 

 in e is smaller than in d. We can say, therefoi-e : 



the solution saturated with a component and with one of its 

 hydrates has a lower pressure than the pure solution of the hydrate. 

 The same considerations apply also when two hydrates of a same 

 component occur. 



We may summarise the previous results in the following way. 

 Through each solution saturated with two solid substances go two 

 salurationcurves; when we limit ourselves to the stable parts of 



