EXPANSION OF SOLUTIONS OF COFPER SULPHATE. 



75 



Thus the rate of change of density with temperature for a given temperature increases 

 in general with the percentage of salt in solution. It will be noticed that there is a curious 

 break in the continuity of the values of this rate for the temperature 20' 0. The first six 

 curves, in fact, differ in form from the rest. 



A slight manipulation of the above results will shew clearly the peculiarity of solu- 

 tions of sulphate of copper referred to above. The following table gives (1) the values of 

 the specific volume {i.e., volume in c.c. of 1 gramme) of the above series of solutions at 25" 

 C. ; (2) the values of the quotient of the total mass of water present in unit mass of the 

 solution at 25° C. by the density of water at that temperature, i.e., of the volume of water 

 at 25° which must be added to the mass of anhydrous sulphate contained in unit mass of 

 the particular solution to produce a solution of the same constitution ; (3) the differences 

 between these volumes : — 



The differences of the above table are, for weak solutions, negative. Hence, assuming 

 as mentioned above, that the same solution is produced by adding a given mass of crystal- 



