282 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XXV. — On the Compressibilities of Dilute Solutions of certain 
Inorganic Salts. By W. Watson, M.A., B.Sc., Carnegie Research 
Fellow in Physics, 1910-1912. Communicated by The General 
Secretary. 
(Read May 5, 1913. MS. received May 6, 1913.) 
The experiments to be described in this communication were undertaken 
with the purpose of obtaining values of the compressibility of certain salts, 
the volume of dilute solutions of which is less than the volume of the con- 
stituent water. The densities of such solutions, chiefly hydroxides, sulphates, 
and carbonates, are discussed by MacGregor * in a series of papers published 
in the Transactions of the Royal Society of Canada ; and Kohlrausch j- 
includes several of them in his paper on the density of dilute solutions. 
We have indirect information as regards the behaviour of such solutions 
under pressure, in the list of compressibilities given by Rontgen and 
Schneider.^ From that list, which I shall refer to later, we see that the 
compressibilities of the hydroxides, sulphates, and carbonates are the 
smallest of those investigated. Such solutions, then, are furthest removed 
as regards compressibility from the solvent water, and it was thought 
interesting to choose examples of these solutions for a more comprehensive 
investigation of compressibility. 
The connection between compressibility and internal pressure and other 
physical properties is very important because of the light it throws upon 
chemical constitution, and from this point of view Richards and Stull § 
carried out a series of researches on compressibility, chiefly devoting them- 
selves to the compressibility of the elements. Tammann, again, from 
another point of view, has drawn up a table of internal pressures of various 
solutions calculated from the thermal expansion, and he tests his results 
by the measurements, among others, of Tait, Amagat, and Rontgen and 
Schneider. The researches of the first two were mainly on water. The 
work of the latter has already been mentioned, but it and similar researches 
on the same lines by Pohl [| and Schumann If were all made at comparatively 
low pressures, a few atmospheres at most, and, in Rontgen’s case at any 
rate, for only two different concentrations. My object, then, was, instead of 
taking a large number of substances and one or two concentrations of each, 
* Trans. R.S. Canada , 1889, etc. t Annalen der Physik und Chemie, 1894. 
% Ibid., 1886. § Zeitschrift fur physikalischen Chemie , 1902. 
|| Inaugural Dissertation, Bonn, 1906. 1" Annalen der Physik und Chemie, 1887. 
