42 



WILSON 



AET. C 



At the critical point Vi = V2, log P = 0. We may take P ^ 1. 

 Furthermore 



and" 



F3 = 



a iVi + 1)2 {V2 + 1)2 

 /^i 7i + F2 + 2 



bpViV2 V,V2 - 1 



The critical locus may therefore be plotted from the following 

 computation form 



* The intermediate value V3 where the ascending branch of the iso- 

 thermal cuts the horizontal is obtainable from 



bWiViVz = ViV2Vi — b{viVi + i;ij;3 + r2f3) + b^ivi + fj + Vz) — b^ 

 which may be evaluated at once from van der Waals' equation. 



