( 684 ) 
of two parts, both of them being positive. Water below 4° is theré- 
fore a substance, whose energy decreases, if it extends at constant 
temperature. Though the molecules of water cohere strongly, it 
‘behaves in this respect as if a repulsion between the particles 
existed. As this repulsion is, no doubt, only apparent, it appears 
to me that this loss of energy cannot be explained otherwise, than 
by assuming that in this case extension causes the complexity to 
increase; and this again makes us suppose that the volume of 
water molecules increases, when they associate to more complex 
Systems. 
For a mixture, either binary or ternary, the process, for which 
(&aj)o represents tlie loss of energy, might be divided into three parts. 
Between the two operations, mentioned in the case of a simple 
substance, we have to insert here the mixing of the first phasis 
with the condensed second phasis; but the change of energy 
arising from this mixing, may be considered to be small, even 
compared with ég,—é,. I have discussed this point rather elaborately 
in order to strengthen the conviction that (€))o < 0 is the general rule. 
Yet it remains of course the task of the experiment to inquire 
into those cases for which this rule fails. 
From equation (1) of the preceding communication we find the 
connection between the sign of (é9,)» and the way in which the 
coexistence surface changes its place at increasing temperature. 
This connection is expressed by the following equation: 
02 w ; Ow eer, dw ) 
vo) ( dv,” a ei Ov; de, den MA dv, Oy ayn ae 
AOS ACLS ow WREE 
si (x2 vj) (dv, Or} dv, a dar? de, + Oy Oe: dn, == 
ER eat rn Ol ee ee 
+ (y2—1) Fn do + eo day + aye dy) ==. = (aoa 
If 7 is kept constant, dx, dy, and dv, represent the projections 
of an element situated in the coexistence surface. But if d7’ differs 
from zero these quantities represent projections of a small line, 
connecting a point of the second surface (that for the temperature 
TdT) with a point chosen on the first surface (that for the 
temperature 7’), We choose the point on the second surface such 
that it lies between the nodes, on the right line connecting them, then: 
dv, ss dx, dy; 1 
— ~ —— 
PV B Ya À 
4 being positive. The first member is positive in consequence of the 
stability of the phases of the coexistence surface. If (ej) is negative 
