456 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXX. — Isopiestic Expansibility of Water at High Pressures and 
Temperatures. By W. Watson, M.A., B.Sc. ; 1851 Exhibition 
Research Scholar, 1900-1910. ( Communicated by Professor J. G. 
MacGregor.) 
(Read February 6, 1911. MS. received February 13, 1911.) 
These experiments were made in the Physical Institute of the University 
of Leipzig at the suggestion of Professor Des Coudres, who very kindly 
placed at my disposal for the purpose a compression-cylinder suitable for 
high temperature work, which I shall describe later. The original 
description by Professor Des Coudres appeared recently in the Berichte 
der mathematisch-physischen Klasse der Koniglichen Sachsischen Gesell- 
schaft der Wissenschaften zu Leipzig , vol. lxii., 18th July 1910. 
Previous Work ok the Subject. 
To investigate the volume of water above 100° C., we must submit 
it to pressure in order to avoid vaporisation. Hirn * kept the water 
under the pressure of about 10 metres of mercury and worked up to 
temperatures of 200° C. He calculated out a formula of the form 
V T = V 0 (1 + at + bt 2 + ct 2, + d&) and found the values of the constants a , b, c , d 
for temperatures ranging from 100° to 200° C. 
Waterstonj- investigated the water in a closed graduated glass tube 
with thick walls. Correcting for the mass of vapour which was always 
unavoidably present, he found the volumes of water up to 320° C. 
Amagat’s J great work on the compressibility of water, ranging to very 
high pressures, gives us data from which, at various pressures, we can 
calculate the specific volume of water at temperatures up to about 200° C., 
the observations being specially exhaustive between 0° and 100° C. 
In the experiments of Hirn and Waterston the pressure is comparatively 
small and the temperatures never exceed 320° C. ; in Amagat’s, the pressures 
are in general high and the temperatures have an upper limit at 200° C. 
The experiments with which this paper deals bear a certain resemblance 
to Amagat’s in this respect, that the pressures are invariably high, having, 
* Ann. Chim. Phys. (4), 10, 32, 1867. 
t Phil. Mag. (4), 21, 401, 1861, and 26, 116, 1863. 
f Ann. Chim. Phys. (6), 29, 551, 1893, etc. 
