Section III? 1889. [ 23 ] Trans. Roy. Soc. Canada. 



VI. — On. the Yanutiou of the Demit ij- with the Guiicoilmlion of Weak A/jveoas 

 Solutions of Certain Salts. By Pkof. J. Gr. MacGke<,;ok, D. Sc. 



(.Hua.1 May 8, ISSi).) 



Tu a paper on " The Density of Weak Aqueous Solulious ol Certain Sails," ' whicli I. 

 had the honour of laying belore the Royal Society of Canada in 1885, I pointed out, as an 

 incidental result, that in the case ol' Zinc and Magnesium Sulphates, the increase in 

 density produced by adding the anhydrous salt to water was proportional, or very nearly 

 proportional, to the amount ol'salt added, provided the solutions thus formed did not con- 

 tain more than about 2 or 1 per cent, respectively of salt. 1 have recently had occasion to 

 make a number of determinations of the concentration and density of dilute solutions of 

 the above salts and of several others, and to hunt out similar determinations by other 

 observers : and the data thus obtained enable me to settle, in the case of a number of salts, 

 the limits of concentration within which this simple proportionality holds. 



The solutions which I examined myself were made by mixing weighed quantities of 

 the crystallised salt with weighed quanties of water. The salts had been purchased as 

 pure, and had been re-purified by crystallisation. The water had been carefully distilled. 

 In the case of Iron Sulphate solutions it was boiled, in order that the solutions employed 

 might contain but little dissolved air. 



In all cases, at least two solutions of any one salt were prepared by mixing weighed 

 quantities of the salt and of water. Usually the other solutions required were prepared 

 by diluting one of these with water, or strengthening it by adding salt. In the case of 

 Iron Sulphate, all the solutions used were prepared by mixing salt and water directly, 

 this course being pursued in the case of this salt, because of the fact of its undergoing 

 progressive decomposition after being dissolved in water, and of the consequent necessity 

 of determining the density of a solution as soon as possible after the solution had been 

 formed. 



In preparing the solutions, all determinations of mass were made by the method of 

 double weighing and all weighings were made in stoppered bottles. The weighings 

 were of course reduced to vacuo. The errors of the standards employed were neglected. 

 The balance used was a delicate one made by Collot of Paris. In calculating the per- 

 centage of anhydrous salt in the various solutions, the values of the atomic weights given 

 in Clarke's " Constants of Nature " were employed. 



Densities were in all cases determined by means of a specific gravity bottle. The 

 bottle used had a volume of about 50 cu. cm. It was of thin glass, but was not so thin as 

 to be readily deformable, and was provided with an accurately ground, perforated glass 

 stopper. AH determinations of density were made at 20°C. A bottle containing the 

 solution and a thermometer, was placed along with the specific gravity bottle in a bath 



'■ Traus. Roy. Soc. Canada, vol. iii (1885) sec. iii, p. 15. 



