( 890 ) 
Hence the colouring particles are occluded in the ice in a dry con- 
dition. Now if this lump of ice is taken from the freezing bath in 
which it certainly had a temperature of several degrees below zero 
and is placed in a heated room, it is coloured blue in a few minutes. 
Hence the colouring particles have caused the ice round them to 
melt and have dissolved. This change occurs so rapidly that we 
cannot think of heat conduction. If now a metal wire is present at 
the interior, this wire will also receive heat through radiation. (At 
the same time it then becomes clear why a silver wire, as was 
found in the former experiments, sinks less quickly through the ice 
than a steel one’). -1 must add that in my experiments an incan- 
descent gas-burner was placed at a short distance from the piece of 
ice for illumination. 
QuINCKE sees in the spots with different refraction above the wire 
solid masses of foam and oily salt-solution. My experiments show 
that if it be allowed to speak of salt-solution, it certainly is not 
solid. But these experiments do not support the view that we have 
salt-solution here, for then a difference in the rate of descent would 
certainly have been found between the ice from the salt-solution 
and the ice from carefully distilled water. The difference in refraction 
between water and ice is great enough to render the separating 
surface between them visible. Of course this does not affect the 
whole of Quinckn’s theory which is founded on an extensive experi- 
mental material of which the phenomenon dealt with in this paper 
is only a subordinate part. 
Physics. — ‘Contribution to the theory of binary mixtures”, XV. 
By Prof. J. D. vaN DER WAALS. 
SPLITTING UP OF THE SPINODAL LINE. 
In the two preceding contributions | have given a description of 
some shapes of plaitpoint lines for not perfectly miscible liquids. I 
had suspended the investigation how these shapes depend on possible 
values of «, and «€, in order to describe more fully the shapes 
of plaitpoint lines obtained by the aid of the theory. And in this 
description I have for a moment, especially in the case of fig. 41, 
no longer anxiously questioned whether this plaitpoint line can actually 
occur on the supposition of positive e‚ and e,‚. So I shall have to 
revert to this question later on. But as another very important case 
Vv 
1) These Proceedings 1907, p. 723. 
