84 



the change of volume, when one quantity of vapour is formed at the 

 reaction, L V^ , tlien L ]\ is always positi\e, except when the 

 liquid is represented by a point of the fourphase-curve between the 

 point of maximumtemperature and the intersectingpoint of this curve 

 with the line FF' . When we now apply the rule: "the equilibria, 

 "which arise at increase (decrease) of volume, are stable under lower 

 (higher) pressure", we may easily refind the above-mentioned rules. 

 When we take as an example ü(j;. 3 in which the case sub 1 

 occurs, the equilibrium F' -\- F" ~\- L -\- G is reju-esented by curve 

 pq, which intersects the line F'F" in »S'; /i' is the point of maximum- 

 temperature of this curve. Consequently LV' is posiiive on pH and 

 Sq, negative on US; the solutions of pH are rich in water, those 

 of jfiq poor in water. When we take a liquid rich in water, the 

 reaction is: 



L:^F -^ P'-f G. Lv.yo. 

 F' + L + (; 



F" ^ L -h G F^F' -\- G. 



F' -f F" + L 

 As the reaction {)roceeds from left to right with increase of volume 

 (A Fi ^ 0), the equilibrium to the right of the vertical line occurs 

 on decrease of pressure and the equilibria to the left of the vertical 

 line occur on increase of pressure. Therefore, from each point of 

 t)ranch pQ the e(piilibria /"' -\- L -\- (i and F" -\- L -\- G pi"Oceed 

 towards higher pressures; consequently we tijid the rule 1". 



When we take a liquid poor in water, this is situated on HS or 

 on Sq. When it is situated on HS, the above-mentioned reaction 

 applies also, but LV^<:^{). Tlierefore, from each point of branch 

 HS the equilibria I'' -\- L -\- G and F" -\- L -\- G proceed towards 

 lower pressures; this is in accordance with rule l'^. 



When we take a solution of branch Sq. the reaction is: 

 F' -f F" :^L-{- G. L r,>o. 

 F' _^ p' _f L F -^L^G 



p j^l7" j^ C; F" j^ L-^ G 

 As the reaction i)rüceeds from left to right with increase of volume 

 the equilibria to the right of the line occur with increase of volume. 

 ' In accordance with rule V' we tind, therefore, that the equilibria 

 F' -\- L -\- G and F" -\- L -\- G proceed from each point of the 

 branch Sq towards lower pressures. 



Now we have deduced the rules V' and \'' assuming that point H 

 is situated on branch pjS; we may act in a similar way when point 

 H is situated on branch qS. In a similai- way we can also deduce 

 the rules 2 and 3. 



