92 



white, unless coloured a little, with Iron or Copper. Sul- 

 phate of Copper is always much bluer, and approaches the 

 Sulphate of Iron, if adulterated by Iron, which often hap- 

 pens. Spec. Grav. of Sulphate of Iron 1«83. 

 Analysis according to Kirwan : 



Oxide of Iron .... 28 



Water 46 



Sulphuric Acid .... 26 



100 



