368 SOLUTIONS OF CERTAIN HYDROXIDES—MACGREGOR. 
ART. V.—ON THE RELATIVE BULK OF AQUEOUS SOLUTIONS OF 
CERTAIN HYDROXIDES AND THEIR CONSTITUENT 
WaTER. By Pror. J. G. MacGregor, D. Sc., 
Dalhousie College, Halifax, N. S.—(Plate I). 
(Read 10th February, 1890.) 
Thomsen,* in the course of his thermo-chemical work, found 
on determining the specific gravities of solutions of sodium hydrox- 
ide in water, of known composition, that in the case of dilute 
solutions of this substance, the volume of a solution was less than 
the volume of the water which had been used in its preparation. 
This seems to me so important a result that I have thought it 
desirable to check it by the aid of other available observations, 
and to determine whether or not it applies also to other hydrox- 
ides. The only other observations of the specific gravities of 
solutions of hydroxides to which I have access, and indeed of 
which I know, are those of Kohlrausch ;+ and although they do 
not include all the hydroxides, they enable us to verify Thom- 
sen’s observations, and to make the desired determination in the 
case of three others. 
For this purpose I have calculated, with the aid of the data 
furnished by both the above observers, the volume of unit mass 
of the various solutions examined by them, and the volume 
which the solvent water contained in unit mass would occupy 
if its temperature were the same as that of the solution. The 
difference of these quantities gives at once the amount by which 
the volume of unit mass of the solution is less or greater than that 
of the solvent water employed in its preparation. There is one 
difficulty in making the necessary calculations from Thomsen’s 
data, viz., that he does not say to what standard his specific 
* Thermo-chemische Untersuchungen, Bd. I, p. 47, (1882.) 
+ Wiedemann’s Ann® len, Bd, VI (1879), p, 21. 
