854 



negative part t^ from the F-axis and also a negative part | from 

 the A-axis. The boilingpointciirve is, tiierefore, situated completely 

 outside the triangle. Considering only the stable parts, therefore the 

 parts of these curves situated within the triangle, we can say : 

 On decrease of P the boilingpointcurve disappears m B;- 

 On increase of P it ai-ises in B and shifts from this point into 

 the triangle. 



The direction of the boilingpointcurve in the vicinity of B is 



determined according to (10) by A W^ and A TF,,. If we put — > — 



y ^ 



then it follows in absolute value A IF,/ > A 11".,. If we call the part, 

 which the curve cuts off from the A'-axis {BA) §„ and the part 

 which it cuts off from the )^-axis {BC) ti^- tlien follows from (10) 



— is the ratio of the quantity of C in the vapour and in the 



y 



liquid, when we add a little C to the unary system solid B + 

 liquid B + vapour B; we shall call this ratio the limit-ratio of C 

 in the equilibrium solid B -\- liquid B -\- vapour B. The same 



applies to— on addition of A. We may now express what precedes 



in such a way : when in the equilibrium solid B -{- liquid B -{- 

 vapour B the limit ratio of C is greater than that of A, the boil- 

 ingpointcurve cuts off a smaller part from the side BC than from 

 the side BA. 



The above-mentioned rule applies only when AWx and APF^are 

 both negative, therefore, when the P, 2 -curve of each of the two 

 binary systems B -\- L -\- (t proceeds from B towards higher 

 pressures. 



In tigs. 4 — 6 in B is assumed — > — in accordance with this 



.'/ «'''' 



the boilingpointcurve, situated in the vicinity of B cuts off from 

 BC a smaller part than from BA. 



When we take A TFx and ATF,, positive, we have the case sub a. 

 From (10) and (11) it follows that the boilingpointcurves in the 

 vicinity of B have the sanie position as in the case sub c; on change 

 of F they move, however, in opposite direction. On decrease of F 

 they shift viz. from B into the triangle and on increase of F they 

 disappear in B. 



When we take also here — >-, it follows that ATFy<ATFr; we 



y -■''■ 



now tind : when in the equilibrium solid B + liquid B ~\- vapour B the 



