16 



J. G. MACGEEGOR ON DENSITY OF 



If Mr. Morrison's observations be plotted so as to form a curve of densities versus con- 

 centrations, the points by which, they are indicated will be found to lie practically on a 

 straio-ht line, passing through the point for which the concentration is zero and density 

 0-99827, this being the density of water at 20' C, according to Volkmann.' Such curves 

 rarely continue to be straight (to the fourth decimal of the density in. grammes per cubic 

 centimetre) at hin-her concentrations than that of Mr. Morrison's most dense solution." Favre 

 and Valson's observations show that nickel sulphate is not peculiar in this respect. The 

 points o-iven by them (approximate allowance being made for the slight difference in 

 the temperature of the experiments) are found to lie on a curve continuous with Mr. Mor- 

 rison's and bending gently towards the axis of densities. The point given by Nicol's 

 observation does not lie quite so well on the curve as the others ; but it is not f;ir off ; 

 and the close a"-reement of the other five observations would seem to warrant our usiag 

 them to determine the amounts of the contraction exhibited by dilute solutions of various 



strengths. 



If therefore, we plot a curve of " expansions " versus concentrations, we may read off 

 from it the expansions corresponding to diflferent degrees of concentration. These are 

 given in the following table : 



' ' Wied Ann.,' Bd. xiv (1881), p. 260. 



2 See my paper, 'Trans. Koy. Soc. Canada,' vol. vii (1889), Section iii, p. 23. 



