Mr Graham on Water as a Constituent of Salts. 309 



Anhydrous 

 Salt. 



Dried on water-bath at 212°, for three days, \ 

 or till it ceased to lose weight, ... J 



Dried on nitre-bath at 238°, for three days, 



Dried in vacuo over sulphuric acid for seven") 

 days, or till it ceased to lose weight ; > 

 therm, from 65° to 74°, j 



Crystals pounded, and slightly dried at 80°, ") 

 so as not to injure the lustre of an entire > 

 crystal, ) 



Same crystals not deprived of mechanical wa- 

 ter by the above treatment, .... 



Composition of sulphate of copper and potash 

 with two atoms of water (by theory), . 



Composition of do. with six atoms of water 

 (by theory), 



196 

 2206 



22.97 



13.94 

 23.79 



Water. 



2.21 



2.37 



1.61 



3.4 

 8.64 



Anhydrous 

 Salt. 



Water. 



100 

 100 



100 



100 



100 

 100 

 100 



11.27 

 10.74 



7.09 



32.25 



36.22 

 10.77 

 32.33 





I have confirmed the observation of Berzelius, that a con- 

 centrated solution of this salt, when boiled, deposits an insolu- 

 ble subsalt, containing sulphate of potash, but which is decom- 

 posed by washing, and cannot be had in a proper state for ana- 

 lysis. But the crystals of the double salt are quite soluble after 

 being heated to 212°, so that they do not undergo the same 

 change as their solution does at that temperature. 



This double salt retains its blue colour after being fused at a 

 red heat and cooled, and does not become white like the sulphate 

 of copper. Indeed it appears, that, to be coloured, the salts of 

 the oxide of copper require the addition of some other constitu- 

 ent, such as saline water, sulphate of potash, or ammonia. Hence, 

 if the absolute sulphate of copper could be obtained in a crystal- 

 lized state, it would be a colourless salt. 



Sulphate of Copper with Sulphate of Soda : CuS(NS)+H 2 . Sul- 

 phate of Copper and Soda. 



Like the other double salts of sulphate of soda, this salt can- 

 not be formed directly, being decomposed by water. Even when 



