83 



these curves, we may saj' (liat two satnrationcnrves proceed fi-om 

 such a solution. Tlien we may say : 



1. The two solid substances are situated in opposition wilh respect 

 to the line LG. 



a. The solution saturated with these substances is i-ich in water. 

 The pressure increases from this solution along the two satura- 



tioncurves. 



b. The solution saturated with these substances is poor in watei'. 

 The pressure decreases from this solution along the two saturation- 

 curves. 



2. The two solid substances are situated in conjunction with 

 respect to the line LG. 



a. The solution saturated witli these sul)stances is rich in water. 



The pressure decreases from this solution along the saturation- 

 curve of that solid substance vvhicli is situated closest to the 

 line LG; the pressure increases along the other satui-ationcurve. 



b. The solution saturated with these substances is poor in water. 

 The same as sub 2''.; we must take however the changes of 



pressure in opposite direction. 



3. The two solid substances are situated on a straight line with 

 the vapour. 



The pressure increases from the solution saturated with these sub- 

 stances along the saturationcurve of the substance with the largest 

 amount of water, it decreases along the saturationcurve of the sub- 

 stance wilh the smallest amount of water. 



We tind examples of 1" in the equilibria : 



F^F'-i-L,^G (fig. 1), F^F"-\-L,+ (; (lig. 1), J+Z^ +/.,,+ (; 

 (figs. 1 and 2), r^F"-\-L„,Jr(^ (<ig'- 3), A+B-^-L.+ G (fig. 5) and 

 F+A-]-Lf^G (fig. 5). 



We find examples of 1^ in the equilibria: F-\-F'~\- L,j-\-G (fig. 

 1), F^F"-i-Li-^G (fig. 2) and F'-^F"-{-Lo^(; (fig. 3). ' 



An example of 2^' is found in the equilibrium F-\- F' -\- Lr-{- G (fig. 1). 



We find examples of 3 in the ecpiilibria : F-{- F' -^ Le-\- G (fig. 4), 

 I^-]-F'^Lf-\-G (fig. 4) and BJ^F-]-L,-^G (fig. 5). 



We may deduce the above-mentioned rules also in the following 

 way. We shall viz., while the temperature remains constant, change 

 the volume of the system F -^ F' -^ L -\- G, so that a reaction 

 takes place between the phases and there remains at last a three- 

 phase-equilibrium. As this leactiou is determined b}^ the position of 

 the four |)oints with respect to one aiuilher, we may immediately 

 distinguish the above-mentioned cases 1, 2, and 3. When we call 



6* 



