dv,2 
Therefore if the first phasis is a liquid phasis,!) p decreases if 
we move in a straight line towards the coexisting phasis, and vice 
versa. (See i. a. fig. 2 of our previous communication). If both 
coexisting phases are situated on the liquid sheet, this applies as 
well to phasis 1 as to phasis 2. So in this case we have v3; = vg > 0. 
And if both coexisting phases are to be found on the vapour sheet, 
then v2 = vj < 0. 
As to the sign of Wo}, this quantity is negative, if the first phasis 
lies on the vapour sheet. It consists in this case of two parts, 
namely (é;), and 7 € v1, Which are both negative. Also Wa, is 
v 
negative, if the first phasis is represented by a point on the contour 
(critical tangent point). In this case vj, — 0 and Wa, = (é))y SO 
it is negative. If the plaitpoint is to be found on the vapeur sheet, 
then for that point Wa, = 0, but at this value again no transition 
from negative to positive values takes place. For points on the 
liquid sheet Wo, may be either negative or positive. Ws, consists 
then of two parts, one of which is negative, the other positive. The 
value of W 3, may reverse its sign either between the plaitpoint and 
the tangent point or beyond those points. So we have, if 7 is chosen 
so high that it does not cover any more the whole triangle OXY; 
the following loci on the coexistence surface: 1st contour for the 
points of which wo, is equal to zero; 2nd the series of plait- 
points, which lies either exclusively on the liquid sheet or on the 
vapour sheet. For the moment we will not discuss the case, that this 
series of plaitpoints passes through the contour. For the plaitpoints 
var as well as Wo, vanishes, but the ratio 23 has a finite value, 
21 
which we will determine presently; 3rd the series of points for which 
Ws, is equal to zero. If the temperature rises, the coexistence 
surface contracts, and the three loei mentioned are displaced, so a 
point whose projections 2; and yj are given lies successively either 
on the second or third locus and on the contour. If 7 rises still 
1) For simplicity’s sake [I call “liquid phasis” each phasis, which is represented by 
a point on the sheet of the small volumes, In the same way L call vapour phasis 
each phasis, which is represented by a point on the sheet of the large volumes. 
