( 64 ) 



mighl -peak of an abnormal, or as I did in preceding pages of this 

 communication, of a complex plait. It' the spinodal curve has split 

 up at certain value tit" '/', which ma\ take place in consequence of 



'h' 



the curve =0 having split tip, there are two plaits, one of which 

 dv 



mighl be called the right plait, and the other the left plait. It' it 



has split up in consequence of a separation between the curves 



= () and = •'. we might distinguish the two plaits by the names 



dv dx % 



"transverse plait and longitudinal plait". Every time that the sepa- 

 ration into two plaits takes place, two homogeneous plaitpoints make 

 their appearance. With transition of a normal plait to a complex one 

 a couple of heterogeneous plaitpoints appear. It' then we wish to 

 pay attention to properties of the binodal curve, other names mighl 

 be though! desirable, but then it would he advisable to state dis- 

 tinctly that this is done to call attention to the special shape of the 

 binodal line. 



The equation d J/ U "i — vdp — ''"fy simplifies for a simple substance 

 to dM l (i l =vdp, and may be considered in this form to lead to the 

 construction for the point of coexistence. This construction can he 

 carried out directly if as axes a p-axis and a Af^-axis is chosen, 

 in which case we gel a curve intersecting itself Cont. II p.4fig.l), 

 or we can choose as axes a /'-axis and a /'-axis, and apply the 

 law of Maxwell. In the latter case we think dAI 1 pi l = vdp writ- 

 ten in the form: d M 1 [il 1 = d(pv) — pdv, the integral of which is 



I, 



(A^fOi — P*if*i)« = (P°)l> ~ (P v )a — I l" lr - F° r coexistence we must 



a 

 have {M 1 (i 1 )b = (M^i)a, and p a = pi = jJCoex, so that we get: 



'-b 



Pc (v b — V a )= I pdv. 

 v a 



For a binary mixture we gel for the determination of coexistence, 

 so for the determination of the points of the binodal curve, the same 

 simple equation : 



«Ll/jf», = vdp, 



when following the series of points for which dq = and so a 

 q-line, in the execution of the construction. 



Let us assume that we wish to apply Maxwell's law. Then fol- 

 lowing a ff-line, we draw the value of // at every value of r, and 



