12G 
DR. WALTER WAHL: PHYSICO-CHEMICAL DETERMINATIONS 
(2) 21ie Glass Windou ' S . — Amagat states, in liis first paper on the solidification of 
liquids l)y pressure, that he observed the liquid and the resulting crystals l)y means of 
a small glass window inserted into the wall of the pressure chaml;)er in which the 
liquid was compressed. In form the windo^v was a ti'uncated cone, the smaller base 
being towards the observer. It wms made of annealed glass, and was surrounded by 
a thin enveloping cone of ivory. With this arrangement of tlie windows Amagat 
was able to reach pressures of aloout 1,200 atmospheres. In the lai'ge series of 
measurements on the compressibility of liquids by the “ methode des regards,” 
Amagat used cylindrical windo\vs which ’were fixed simply loy marine glue, this part 
of the apparatus always loeiug kept cool, so that tloe marine glue did not get too 
soft. Experiments witli windows fitted in this way were carried out up to 1,000 
atmospheres. Later, also, Amagat used similar cylindrical windows, fitted with 
marine glue, for the measurement of the influence of pressure upon tire freezing-point 
of water. In this paper Amagat states that he had met with vei'y serious difficulties 
in getting tlie windows to withstaiid higher pressures tlian 1,000 atmospheres. 
Some of them stood 1,400 atmospheres, and in a single case he had even been aljle to 
carry tlie pressui'e up to 1,700 atmosplieres liefore the glass was cracked, but 
generally about 1,200 atmospheres was the pressure-limit reached, and the work 
was then entirely given up by Amagat. 
The first bomb intended for this researcli was constructed on the same principle as 
the bomb employed by Amagat in his earlier work. The method of gluing in the 
glass windows later used by Amagat would not permit work at higher temperatures 
in the case of the windows being close to each other, as is necessary in some cases of 
crystal-optical research, where the objective of the polarization instrument must be 
brought as close as possible to the crystal or section investigated. The “windows” 
were truncated cones 15 mm. tliick, the diameter of the inner base being 10 mm. and 
that of the outer 7 mm. The enA’eloping conical mantle of ivory was about 1'5 mm. 
thick. The first cones tried were made out of an optical borosilicate-glass from 
Schott & Genossen, of Jena. In polarized light they very soon showed vivid 
polarization colours when pressure was increased, and at about 900 kg./cm.^ it became 
very difficult to see through them at all, ljut apparently tliey did not crack, and 
pressure was carried up to 2,000 kg./cmd —-the limit for which the then used pressure 
apparatus had been tested—the apparatus being perfectly tight all the time. On 
relieving pressure, the compressed oil in the bomlj, however, Ijegan to leak out at the 
windows, and wlien the apjDaratus was unscrewed it was found that the window 
cones now consisted of a very great number of tliin plates, with surfaces as smooth as 
if polished. Some of these glass plates were very thin, others a millimetre or more 
thick, and it was possilJe to further cleave these Ijy pressing a knife against the 
conic side of such a piece, tlie glass, after liaving been compressed in this way, thus 
behaving very much like mica. Tests were then made with different kinds of glass 
for cones and different material for the conical envelopes, soft ebonite and moderately 
