Section III, 1891. [ 15 ] Trans. Rot. Soc. Canada. 



III. — On the Density of Weak Aqueous Solutions of Nickel Sulphate. 



By Professor J. Gr. MacQregor, D.Sc, Dalhousie College, Halifax, N. S. 



(Read May 29, 1891.) 



lu a paper which I had the honour of reading before the Eoyal Society of Canada last 

 year^ I gave the results of observations of the density of dilute solutions of various sul- 

 phates in water, made with the object of determining how many of them form solutions 

 having a smaller bulk than their constituent water would have in the free state. Among 

 those which were found to do so was nickel sulphate, and by means of a single observation 

 made by Dr. W. W. J. NicoF and two on somewhat strong solutions made by Favre and 

 Valson,^ I formed a rough estimate of the limit of concentration within which such solu- 

 tions were formed, and of the magnitude of the contraction in the case of the one which 

 exhibited it to the greatest extent. The estimate was necessarily rough, however, because 

 (1) the number of available observations was small ; (2) Ihey were made by different 

 observers, at different temperatures, with different samples of salt ; and (3) only two of 

 them were within the limit of concentration referred to. It has, therefore, seemed to me 

 to be desirable that a few observations should be made on dilute solutions of this salt, 

 that the magnitude of their contraction might be accurately determined and compared 

 with that of sohitions of the closely allied salt, cobalt sulphate. 



Mr. A. M. Morrison, B.A., has accordingly made for me determinations of the density 

 and percentage composition of three dilute solutions of nickel sulphate. These were 

 found to agree so well with Favre and Yalson's similar observations for less dilute solu- 

 tions, that more were not necessary. Mr. Morrison's method and instruments were the 

 same as those described in the paper referred to above, and the same precautions were 

 taken to eliminate errors, as are therein described in detail. His results, alons" with those 

 of Nicol and Favre and Yalson, are given in the following table. The first three columns 

 of the table contain experimental values from which the last three are calculated. The 

 headings of the columns do not require explanation, except, perhaps, that of the sixth, 

 with regard to which it may be stated that the quantities headed " Expansion " are the 

 excesses of the quantities in the fourth column over those in the fifth, and therefore are 

 the amounts by which the volumes of one gramme of the solutions, at the temperatures of 

 observation, exceed the volumes which the water they contain would have in the free 

 state at the same temperature. 



' 'Trans. Roy. Soc. Canada,' vol. viii (1890), Sec. iii, p. 19. 



2 ' Phil. Mag.,' ser. 5, vol. xvi (1883), p. 122. 



3 ' Comp. Rend.,' t. Ixxix (1874), p. 968. 



