OF IRON. 319 



They were in rhomboidal prisms, were transpa- 

 rent, and had a light green colour ; so that in 

 appearance they bore some resemblance to pro- 

 tosulphate of iron. This salt reddened vege- 

 table blues, as is the case with all the soluble 

 salts of iron. Its taste was sweet and astrin- 

 gent, like that of the protosulphate of iron, but 

 harsher. 



34-8 grains of these crystals, dried on blotting 

 paper, were exposed to the heat of a spirit lamp 

 in a platinum vessel. The salt melted, became 

 yellow, then brown, and fumes of nitric acid 

 escaped. The residue was black, had the me- 

 tallic lustre, and was not attracted by the mag- 

 net. It was, therefore, peroxide of iron, and 

 weighed 8 '8 grains, equivalent to 7*92 grains of 

 protoxide of iron. The weight of the nitric acid 

 and water contained in the 34'8 grains of salt 

 was obviously 26*88. Now, the protoxide of 

 iron in the salt was saturated with nitric acid. 

 Hence, it is easy to deduce from the preced- 

 ing experiment the constituents of the salt; 

 namely, 



1 atom nitric acid . 6-?5 



1 atom protoxide of iron 4-5 

 7 atoms water . 8-43?5 



19-6875 



Probably the crystals contained only 7 atoms of 



