Secrion IIL., 1900. [27] Trans. R. 8. C. 
III—On the Relative Bulk of Weak Aqueous Solutions of certain 
Sulphates and their Constituent Water. 
By Cuarues M. Pasua, B.Sc., Dalhousie College, Halifax, N.S. 
(Communicated by Prof. J. G. MacGregor, and read May 29, 1900.) 
In a paper communicated to the Royal Society of Canada,’ Dr. Mac- 
Gregor has shown that in the case of weak aqueous solutions of certain 
sulphates, the solutions have a smaller volume than the water which 
they contain would have in the free state. To determine how many of 
the sulphates exhibit this property, he collected the previously pub- 
lished observations of the specific gravity of solutions of these salts and 
made some additional observations himself. In the case of some of the 
sulphates previously examined the solutions were not sufficiently dilute 
to settle the question under consideration. Accordingly at his sugges- 
tion I have examined the sulphates of sodium, manganese, cadmium, 
and iron (the —ous salt), as in these cases the data did not extend to 
very dilute solutions, and from the data available for the most dilute 
solutions it appeared possible that at a greater dilution the volume of 
the solution might become less than that of its constituent water. With 
this object in view it was only necessary to examine solutions more 
dilute than those referred to in the above-mentioned paper. I have also 
used Dijken’s observations? on ammonium and lithium sulphates for 
the same purpose. 
The salts examined had been purchased as chemically pure, the 
cadmium and manganese from Messrs. Himer and Amend of New York, 
and the sodium and ferrous sulphate from E. Merck, Darmstadt. 
In the determinations of the specific gravity of the solutions, the 
pyknometer employed was of the Sprengel form as modified by Ostwald. 
It weighed about 23 grams, and had a capacity of about 25 cubic centi- 
metres. The pyknometer after being washed out with the solution 
whose specific gravity was required, was filled and placed in a water- 
bath, the temperature of which was kept at 18°C. The water in this 
bath was kept constantly stirred by means of two vanes set obliquely in 
and rotating round, a vertical axis. The stirrer was driven by means of 
a small hydraulic motor. The thermometer employed to indicate the 
temperature of the bath was graduated to fiftieths of a degree centi- 
grade, and its errors had been determined at the Physikalisch-technische 

1Trans. Roy. Soc. Canada (1), 8, Sec. LII., 19, 1890. 
2 Ztschr. f. phys. Chem., 24, 80, 1897. 
