OXIDATIONS OF IRON. 225 



tallic oxides, has been ascribed to oxigen. It has been sup- 

 posed, that all the properties of oxides of iron, both che- 

 mical and physical, are owing to oxigen ; while on the con- 

 trary, from ray observations I am induced to believe, that 

 its part is so passive, as to give it a claim to scarcely any of 

 those properties. 



Notwithstanding the uniformity of the circumstances, to Oxides variable 



which I had subjected the iron in its different calcinations, under similar 

 T _ _ . , , 'circumstances. 



1 observed, that, when 100 grains had taken up 28 of 



©xigen, the oxide was sometimes entirely magnetic ; while 

 at other times, having taken 30 or 32, it afforded a very 

 deep and extremely homogeneous green precipitate; aud 

 lastly that at times the red oxide occurred by anticipation 

 at 28 or 30. As I was prejudiced in favour of the less or M ost p heno« 

 greater divisibility of substances, on which I believe most mena depend 

 phenomena depend, I did not hesitate to ascribe to this biiity^f Tub- 

 cause the results I had obtained: but to satisfy myself on stances - 

 this head, I took 300 grains of iron filings of three different Experiments 



densities, and each portion less dense than that 1 had before wuh fi|in fp of 

 - • ' ./.,., difteientdensu. 



employed. Let us suppose the ratio of t',;cir densities to ties. 



have been at 1, 2, 3. I subjected to calcination the 100 

 grains of the most dense, removing them from the fire every 

 ten minutes, to triturate them in a mortar. At the end of 

 half an hour, and having been triturated three times, they 

 had taken up 24.70 of oxigen, their colour was become al- 

 together red, their magnetism was very weak, and dissolved 

 in muriatic acid they afforded red precipitates like oxide at 

 56- I repeated the same experiment on 100 grains of the 

 second degree of density, and when they had taken up 21 

 of oxigen, the oxide displayed the same properties as the 

 preceding. Finally I subjected to the same proof the last 

 100 grains, which were extremely fine, and which I had 

 previously sifted, that their density might be more uniform; 

 but instead of taking them from the. fire every ten minutes, 

 I triturated them every five, to diminish the action of the 

 oxigen as much as possible. To the space of a quarter of Oxides similar 

 an hour they had taken up 15 of oxigen, and the properties 

 of the oxide were the same as those of the two preceding*. 



Thus 



* Sometimes they contain 2 or 3 per cent of green oxide, which 



is not perceived, and which it is difficult to separate, even though 



it 



