OXIDATIONS OF IRON. 223 



mixture when cold exhibited a brown mass, with a few 

 green and iridescent spots. 



This mass, pounded and washed repeatedly with boiling The oxide 

 water, to divest it of its alkali, afforded me a brown pow- brown ' ma &ne- 

 der, strongly attracted by the magnet, and not soluble in Soluble incold 

 cold muriatic acid. Heated with this acid diluted with a muriatic acid, 

 little water, it afforded a colourless solution, from which 

 alkalis precipitated a blackish brown oxide, that did not Dissolved and 

 alter by exposure to the air, and at the expiration of a few P/ecipitand, 

 minutes, had acquired so great a cohesive force, as to be 

 insoluble in cold muriatic acid. When dried in the air it 

 was magnetic, and indeed retained the same characters as 

 before it was dissolved. * 



As the loss prevented my calculating the quantity of or. 

 igen in this magnetic oxide, while its colour and magnetism 

 led me to conclude, that it contained less than the red, ob. 

 tained by calcining iron filings alone, I proposed to try this 

 method, seizing the moment when the magnetic oxide should 

 be formed. Accordingly I put into a crucible 100 grains 

 of iron filings, and after having kept them half an hour in ipon filings cal- 

 a brisk heat, stirring constantly, I withdrew them, and cine d atone* 

 found the weight 120 grains. I observed on this occasion, 

 that each grain of the filings, though covered with a stratum 

 of oxide, contained a metallic nucleus ; and in order to ex» 

 pose the metal, and accelerate the operation, I triturated 

 these half oxided filings, before I put them again on the 

 fire. On continuing the calcination, and trying the oxide 

 occasionally with muriatic acid, I found the magnetic 



* I fancied this at the time to be a peculiar oxide ; but I after* 

 ward perceived, that its colour and magnetism arose from the con- Cause of the 

 centrated state of the solution and of the alkali with which I precipi- colour and 

 tated it ; since if I diluted the alkali with water, or used lime, stron* 

 tian, or barytes water, the precipitate* were entirely red, 



On mixing green and red solutions of iron in a certain proportion 

 that may be found by trial, we likewise obtain black magnetic preci- other magnetic 

 pitates, that do not change on exposure to the air : but the two phe- oxides, 

 nomena must not be confounded together, for there are magnetic 

 oxides, that do not contain an atom of green oxide. The green 

 salts of iron too may be precipitated so as to be black, magnetic, 

 j>nd unchangeable by the air. 



5 oxide 



