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molecular potential of one of the two components has the same 

 value. We shall call this third group of lines "potential lines". 



The potential lines. 



</![• dip 



The value of }f, n, is equal to tb—.v- >'-;-> ''v drfferentia- 



1 ile (/:/• 



lion we find: 



dy _ ^ d ,/.!• 



or 



<1 M.H, — v dp — asdq 

 It' we wani to know the shape of such a potential line, we musl 



know for such a line, which quantity we shall represent l>\ 



dm ' 



| ). For the value of diis quantity we find then the expression 

 \dteJpot 



./-if ,/uf 



v -f X 



I e \ dr ilr i /,)■'- 



dxjpoi </'-'. I- d*ip 



ilr' il.eile 



which may also be written : 



v dv 



ilr \ ilr x dx 



dxjpot dXp r dv 



dV p 



'dx 



So there is a locus in whose points I \ = y. , and another 



f,lr\ _ v dv 



whose points I 1 = 0. 1 he tornier lakes place when = i.e. 

 \dxJ Pol x dx p 



this locus is the series of points in which lines drawn from the 



fdv\ ilr 



origin touch the w-lines. < >n the other hand =0 if = • 



1 \dxJPot •'■ dx q 



dv ile fdv\ 



tor the points ot the spinudal curse in which — = — , also I 



dx p dx q \dx) Put 



,le 



is equal to — . 

 1 dx p 



The shape ot' the locus v = x\ j is different, according as the 



\dxj p 



//dines have the course as in the left region of the general p-figure, 



or as is the case in the middle region or in the right region. The 



