356 on THE OXIDES O? IRO.V. 



however is much more poM erful when it acts on red tutiAh 

 recently precipitated from a ferruginous salt by means of 

 potash. 



Sulphuric Add and Red Oxide of Iron. 



Action of sul- An ounce of green sulphate of iron dissolved in an ounce 



fed oxide of ^^'^ of witer was made to boil, and six drachms of nitric acid, 



iron. previously diluted with six drachms of water, were added 



gradually. A brownish yellow powder fell down, which, 



after desiccation, weighed 42grs. [-/^ of a drachm, or 35grs. 



Eng.]. It was the neutral red sulphate of iron with excess 



of oxide mentioned by Mr. Thenard. 



The supernatant liquor, of a reddish brown colour, was 

 heated in a capsule ; and immediately a brownish substance, 

 similar to the preceding, separated, which however dissolved 

 in proportion as the liquid evaporated. The thickened mat- 

 ter rapidly attracted moisture from the air, and resumed a 

 sirupy consistence. Sulphuric acid immediately changed its 

 red colour white. Evaporated to dryness with one drachm 

 of sulphuric acid, and heated till all the excess of acid had 

 disappeared, a white powder remained, which exhibited the 

 following properties. 



It was tasteless ; and insoluble in water, either cold or 

 boiling; but the latter deprived it of a little sulphuric acid, 

 and changed its white colour to a brown. 



On agitation with ammonia it changed to a broAvnish yel- 

 low, and the supernatant fluid contained sulphate of am- 

 monia. 



Muriatic acid dissolved it entirely by the assistance of 

 beat, and exhibited a yellowish red liquid. Water acidulated 

 with sulphuric acid had the same effect. 



Here then we have a sulphate of iron of a white colour, 

 in which the oxide is red and at a maximum of oxidation. 



Recapitulation of the Facts in this Paper, 

 General results. ^' There are but two degrees of oxide of iron ; the black 

 oxide at a minimum, and the red at a maximum. No other 

 state of oxidation exists in reality, and what has been taken 

 for oxide has been nothing but a combination of one of these 

 oxides with some acid, or a mixture of them in different 

 proportions. 



2. A 



