OXIDATIONS OF IRON. QJ\ 



yj.sld green or white precipitates. I am inclined to think, 

 however, that this is rather an inference drawn by Mr. The- 

 nard from his manner of considering the white oxide of 

 iron, than a fact that came under his observation. Be this 

 as it may, I can assert, that, having repeated these experi- 

 ments several times, frequently changing the reagents, and 

 varying the circumstances as much as possible, I have ob- 

 tained only green or black precipitates, according to the 

 concentration of the sulphuretted hidrogen, and the quan- 

 tity of the sulphate of iron, presented to each other. If this 

 assertion of Mr. Thenard were a fact he observed, I confess 

 it is an anomaly, for which I cannot account, and which I 

 cannot reconcile with the whole of the facts I have related. 



If all these facts do not controvert the existence of the The existence 

 white oxide, I have still another to add, which not only ? f a S ree P ox * 

 ■controverts it, but even renders that of the green oxide able. 

 questionable. 



Let a phial be fdled with three parts of ammonia, and one 

 of sulphate of iron precipitating white; and let it be corked 

 immediately. At first, a white precipitate will be formed, 

 which on shaking the phial will dissolve in the ammonia. If 

 the oxide of iron be afterward thrown down by means of 

 water or of an acid, it will always be green or brown : and 

 if, instead of precipitating it by either of these means, a 

 small curved tube be fitted to the phial, its extremity be im- 

 mersed in water, and sufficient heat be applied to expel the 

 ammonia; as this is volatilized, a black or brownish oxide 

 will fall down, which, on being dissolved in muriatic acid, 

 will afford precipitates for the most part red. Now it is im- 

 possible here to suspect a superoxidation by the ammonia. 



Add to this, there are likewise salts of red oxide of iron T Xrr ,. t ,. c 

 :•"•-' , White salts of 



with excess of oxide, that are not only white and soluble iron with base 

 like the salt of Mr. Thenard, but frequently crystallize ; of red oxide - 

 that are not deliquescent, like the common red salt of iron ; 

 and that exhibit still other peculiarities. I shall mention 

 these in a paper on another subject, where I shall speak of 

 iron incidentally. Till that occasion, likewise, I shall defer 

 explaining the cause, why some of the white precipitates ob- 

 served by Mr. Thenard retain their colour even after long 



boiling'. 



