( 61 ) 

 junction will lie at larger x than the point of junction of the branches 

 of — = 0. This junction musl then take place in a point of inflec- 



ilr 



ii t' a //-line, a- i- immediately seen when in a p-figure the 



tangents arc drawn from the origin in the circumstances mentioned, 



in which it also appear- that the point of contact then lies on a 



p-line nt' maximum value. So the point of junction mentioned i- a 



point in which tin' tangent of a p-line in its point ol inflection passes 



dv 

 through the origin. From the differential equation ut' v • = 0. 



it' r i- taken a- function ut' x ami /-. follows for this locus 



,r-r 



dp _ il.r*^ 



dx dv d*v 



<//>, dpd.t 



The potential lines of low degree have then lost the points in 

 which they arc directed vertically, and have then a very simple 

 shape. With decreasing volume they no longer run back to smaller 

 value of x. 



In the second place lei us choose a region in the middle, where 



,/ r dp 



the two points of intersection <>l =0 and = arc found. 



dx ili' 



dp 

 Even though the two branches nt = remain entirely separated, 



dv 



dv 

 this is not necessarily the case with the two branches of»- x—— = Q. 



"'■''/' 

 It is easy to see that the branch at the smaller volumes lies above 



dp 



- =0 only from x = to the double point ot the //-lines. With 

 dv ' ' 



higher value of x it lies below it. In the same way the branch of 



dv dp 



v x — =0 at larger volumes lies below — = only from x = 

 dxp dv 



to x of the double point. Tin- lower branch passes through the 



dp 



double point, and lies above — — with greater value of x. I he 



two branches join as soon a- there exists a p-line, for which the 



tangent in the point of inflection is directed to the origin. If at 



. . dp 



minimum critical temperature the line — = posse»e- i splitting 



dv 



dv 



point, the curve /■ — x =0 i- restricted in the left pari, ami is 

 dx» 



