SOLUTIONS OF NICKEL SULPHATE. 17 



Thus the limit of concentratiou within which solutions of this salt have volumes smaller 

 than those of their constitvient water is about *7'35 per cent. The solution which exhibits 

 the greatest contraction is one containing- 35 per cent, of anhydrous salt, and the amount 

 by which the volume at 20' of one gramme of this solution is less than that of its consti- 

 tuent water is 00011 cu. cm. 



"With regard to the relation of the above results to similar results obtained in the case 

 of cobalt sulphate, and published in the paper referred to above, it may be noted that the 

 concentration-density curves of the two salts are almost coincident up to a concentration 

 of about 4 per cent. They may be represented very approximately by the formula : 



D.„=0-9982'7+0-01064/> 



where B.,,, stands for density at 20" C. and /; for percentage of anhydrous salt in solution. 

 They are not quite coincident, however, and the amounts of the contraction in dilute 

 solutions of the cobalt salt differ somewhat from those of the nickel salt. In the case of 

 the former the limit of concentration within which the solutions have smaller volumes 

 than their constituent water is, as shewn in the paper cited above, about 5'5 per cent. ; 

 the solution exhibiting the greatest contraction is one of about 2'8 per cent., and the 

 amount by which the volume at 20° C. of one gramme of this solution is less than the 

 volume of its constituent water is 0'00064 cu. cm. 



Sec. Ill, 1891, 3. 



