260 



PROCEEDINGS OF THE AMERICAN ACADEMY 



Third Series : Results. 



Percentage Composition of Cupric Sulphate. 



The Cause of the Deficiency. 



It was by no means easy to trace the cause of the disappearance of 

 less than one two-thousandth part of the material to its true source. 



The notable agreement between the percentages of water given in 

 the first three columns of figures immediately above of course sug- 

 gested the possibility of a loss of copper and sulphuric acid during the 

 electrolysis ; and it became an important matter to test the point. 



Accordingly weighed portions of a dilute solution of pure sulphuric 

 acid were estimated with weighed amounts of sodic carbonate. Other 

 portions of the same solution, weighed alternately with the previous 

 ones, were then evaporated over the water bath with small amounts 



