16 AKT. 10. — K. IKEDA : STUDIES ON THE 



gas phase will be /', aud the curve will proceed in the direction 

 /'/, etc., etc. 



In the case of an ideal solution we have 

 p, = C\'P = C\P, 



2>, = a/p = ap, 



Ih ■= 0,'P = C,P, 

 and P=CJ\+0,P,+ aj\. 



Hence 



C\P^ 



C\' 



cj\+c,p,+o.A 



62X2 



^' cj\+ap,+cj\ 



As the tangent to the distillation curve passes through the point 

 C[, Co as well as the point C[', C/ we have 



.(7) 



cia _ a- a' _ c,{ca±o,p.,±{i~c\-c.^ p.^-z] 

 dc\ ~ c\-c,' c\{c\p,+c,R+{i-c-a^P-p,] 



Which may also be Avritten 



dc, G,{p~py 



Suppose the first component to be the most volatile and the 

 second component to be the least volatile of the three, then 



P-R>0, P-Pr<0; 



and as both C[ and C2 are necessarily positive 



In other words 62 must decrease as Ci increases. The curve of 

 isothermal distillation has therefore the form represented by 

 (B1ÄB2, etc., Fig. 4. When there is but little ©1 in the solution 



-^77^ must be very large, and when C[ = the curve coincides 



