1021 
Physics. — “Keperimental investigations concerning the miscibility 
of liquids at pressures up to 3000 atmospheres”. By Prof. 
Pu. Koxnstamm and Dr. J. Timmermans. VAN DER WAAIS 
fund researches N°. 4. (Communicated by Prof. vaN per WAALS). 
(Communicated in the meeting of November 30, 1912). 
§ 1. The theoretical researches of the last few years have rendered 
it possible to give a complete classification of the different types of 
unmixing which are to be expected. Whether these theoretical 
expectations are in conformity with reality could be ascertained up 
to now only for a very limited region, on account of the inaccessibility 
to experiment of the whole region of pressures higher than two or 
three hundred atmospheres. The wellknown Camrerer tubes are 
namely useless at higher pressures. We have, therefore, been occupied 
already for a considerable time in devising an apparatus intended 
for higher pressures, and we have finally succeeded in constructing 
such an apparatus, with which we have carried out measerements 
up to 38000 atm., and which can probably also be used up to 4000 
or possibly 5000 atm. 
The first problem that was to be solved was, of course, to render 
the phenomena visible. For, to ascertain the critical phenomena of 
unmixing, and the phenomena of unmixing in general by means of 
other properties than those which fall within the scope of direct 
visual observation, seems. hardly possible. Our first attempts to effect 
this visibility by pressing a thick piece of plate glass 
A (fig. 1) by the aid of a nut B fitting round it, 
against the steel tube which would then contain 
the substance to be examined, or strictly speaking 
Fig. 1 against the packing enclosed between C and A, 
failed entirely. Even the thickest plate glass plates snapped off 
inexorably, when we tried to screw the nut tight enough to prevent 
leakage. 
Led by the figure that Amacar gives for the apparatus of his 
“methode des regards’, with which he has succeeded in carrying 
out measurements up to 1000 atm., we resolved to arrange the 
“windows” in such a way that neither on the front nor on the 
according to this principle; they are nol cones but cylindres, they bear on the 
end-plane directed to tne observer; AMAGAT uses celluloid packing between steel 
and glass. We have, however, experienced that to reach the highest pressures, it 
should carefully be avoided to make the windows bear on their end-plane. 
