148 ON THE OXIDATION OF IRON. 



yet agreed on the proportion of oxigen it contains, some 



making it 42, others upwards of 50. 



The/may vary Your immortal Chemical Statics appeared. The opinion 



progressively . . 



from the least you there advance, that " the proportions of oxigen may 



to the greatest. var y progressively from the term at which combination be- 

 comes possible to that at which it attains its highest de- 

 gree," admits, like that of Proust, a maximum and mini* 

 mum of oxidation, but it differs from him in two respects : 

 he asserts, that these two points are the only ones, and he 

 even fixes them; while you, in addition to the progressive 

 variation of oxigen, leave these two extremes undetermined. 

 Proust strenuously opposed your opinion ;* and I must 

 confess that his reasons, and the facts by which he sup- 

 ported them, staggered me. Thus I wa3 on the point of 

 giving up the oxidation of iron in various degrees, when I 

 read Thenard's Considerations on the oxidation of metals in 

 general, and that of iron in particular f, in which that able 

 chemist appears to adopt a mean opinion between Proust's 

 and yours ; and where he shows, that there is a third oxide 

 of iron, white oxide, which contains less oxigen than the 

 green minimum oxide of the chemist of Madrid. These, 

 with your answer to Proufl:^ and Darso's|j inquiry concern- 

 ing the oxidation of iron, in which he says he has obtained 

 by calcination oxide of iron containing as far as 56 of oxi- 

 gen to 100 of iron, still kept my opinion in suspense. 



Four oxides. ^ the facts related by Thenard and Darso be true, there 

 moist be four oxides of iron : 1, white; 2, green ; 3, red; 

 4, beyond the red as far as 56 of oxigen to 100 of inn. 



_ , As you have quoted the experiment of Thenard, and this 



chemist has the reputation of being accurate in the facts he 

 announces, I am inclined to trust his results. As to that 



r of Mr. Darso, it appears to me the more extraordinary, as 



all the precise experiments hitherto made had not carried 

 the maximum oxide of iron farther than 42 or 45 of oxigen 

 to 100 of iron, and even Proust made it no higher than 43. 



* Journal dePhysiqu*, an. 1804, torn. II, p. 330. 



| An. de Chim. vol LVI, p. 57: or Journal, vol. XIV, p 224 



* Journal do Physique, an. 1005,. torn. II, p. C5G. 



|j Jouru. do Phys. an. 1806, torn. II, p.'s9li or Journal, vol. XVII, 



j.// i, 267, cca! 



Doubting 



