1910-11.] Specific Gravity and Displacement of Saline Solutions. 641 
Table No. 1, class A, already quoted, is an example of one of the tables 
of the Ennead, and relates to chloride of potassium. 
The results obtained with the hydrometer in dilute solutions of the 
Ennead having proved so interesting, I undertook the investigation of the 
more concentrated solutions with the specific gravity bottle or pyknometer, 
using generally the same common temperature T = 195°. The specific 
gravity bottles used held 25 and 50 cubic centimetres respectively. The 
most soluble of the salts is csesium chloride ; 1000 grams of water saturated 
with it at 19*5° C. contains 12T563 gram-molecules or 2048\34 grams of the 
salt. The specific gravities of the solutions saturated at temperatures 
between 21° and 24°, and those of the solid salts which crystallised out of 
them, formed the subject of a memoir read before the Chemical Society of 
London, and published in the American Journal of Science, vol. xxi., 
January 1906. It is entitled, “ On a method of Determining the Specific 
Gravity of Soluble Salts by Displacement in their own mother-liquor ; and 
its application in the case of the Alkaline Halides.” The work then done 
with the saturated solution has now been joined on to that done with the 
hydrometer in dilute solutions, by observations made with the pyknometer 
in solutions prepared so as to contain 1, 2, 3 . . . in whole numbers of gram- 
molecules per 1000 grams of water. By these determinations the specific 
gravity of solutions of all concentrations of the salts of the Ennead has 
been well investigated. 
While it was necessary to use the pyknometer for the concentrated 
solutions of such costly salts as those of rubidium and caesium, it was found 
convenient to adapt the hydrometer, by a slight alteration in the distri- 
bution of its weight, for use in solutions of all concentrations, and so obtain 
results of as high precision in concentrated solutions as I had already 
obtained in dilute solutions. 
In the extended paper many interesting observations on the specific 
gravity of solutions in the neighbourhood of saturation are recorded ; and 
in the case of a supersaturated solution of chloride of calcium particularly 
interesting results were obtained, furnishing volumetric evidence of the 
labour which takes place in such a solution before it finally becomes a 
mother-liquor by giving birth to a crop of crystals. This highly interesting 
quantitative work could not be effected by any other instrumental means 
than the hydrometric method here described. 
In the paper published in the American Journal of Science above 
referred to, the specific gravities of the crystallised salts were determined 
by displacement in their own mother-liquors ; it appeared to be interesting 
to extend this work so as to include the salts of the Ennead of oxyhalides, 
VOL. xxxi. 41 
