(y, -(ï)-(y-(J)| 1=7 ^— ..f . . (22) 



745 



From (18) now follows : 



2RT __ 



From (22) it follows that the saturationcurve under its own 

 vapour-pressure under consideration is in the vicinity of the point 

 H [fig. 4—6 (XI)] a parabola, which touches the side BC in //. 

 From (18) and (20) follows the change of ^ and i] along this curve 

 at a small change of pressure dP. 



We can find the meaning of a (22) in the following way. 



We represent the length of Cp or Cq [fig. 1 (XI)] by Y, the 

 length of the part, which is cut off by the liquid curve of the 

 region L — G from CB by y. Then we have : 



^'dP~ r— /? ~ or "' *dF~~y^^ ^' *'dP~ y^i~J^^ ^'"^^^ 



Herein t^ and V^ refer to the point of intersection of the satura- 

 tioncurve with BC. Now we put : 



Y-y = l 



dl dH 



and we calculate — and . For this it may be considered that 



dP dP^ 



Vq depends on P and Y, V on P and y and V^ on P and y^. 



If now the saturationcurve of F and the liquid-curve of the region 



L — G go both through the point H, then (15) is satisfied; also at 



the same time Fq becomes =rz V and t^ = t. Then we find : 



• < dl - "^ "" '" dH 



— = and a = t{y-^){>i,-y)-^ .... (24) 



Substituting this value of a in (20), we find after deduction with 

 the aid of (13) ^XI) and (11) 



/ S\ dH 



2RT.K\l-~^U = t{y-if,)^^.dP^ . . . (25) 



and 



/ S\ ^ t'i'j-y,) dH 



2ijr.if(^l_-j| = ^i^.^.,f. . . (26) 



["-fj 



wherein ^^0; that there may be agreement with our figures, wo 

 take y — y^ ^ 0. 



We now distinguish two cases. 



48* 



