ON THE OXIPES OF IROy. ]g^ 



in a vewel under ajar filled with oxig^n ga?, and standing 

 over mercury. He found 100 parts of iron increubcd to 

 135 or 13t) in one e3?p^i;iinent, and to 13:i'4l4 in another*. 



This dilferenceof^ results in similar ex peri mwts, show* Remarks <m ■ • 

 the great difficulty of executing them properly :. ancl;«intf)0s>* ^lenls^*' '^"* 

 all that have been mentioned inine is the only one, in winch, 

 the iron appears to ha.ve been carried to its maximum of 

 calcination; us that of Mr. Darso, though indicating a 

 larger proportion of oxigen, 1 conceive to have been inac- 

 curate. In my experiments iron pxided at a maximum ap- 

 pears capable of being carried as far as 45 of oxigen to 100 

 of iron, or about 31'1 of oxigen to 68*9 of iron, which 

 may be called in round numbers 31 per cent of oxigen. 



,As to the other experiments, which cairy the oxidation 

 to 24, 27, 30, 33, and even 38, we may presume, that 

 portions of metal not yet completely calcined still remained 

 among the iron, for on triturating the iron, after each <'al- 

 cinatibn it was observed, that little nodules of iron remained a 

 long timet which the oxigen had not attacked* 



2d Method. Disoxigenation of the oxide hy heat alone, and 

 hy heat and carbon or hidrogen. 



Attempts have frequently been made, to carry back the Attempts t« 

 oxide of iron from its maximum by calcining: it stron£i:Iv, *"'*^'?^^ °'"' 



y " »/• * gen fr(»ia tb« 



either alone, or with substances that have a stronger affinity oxides, ny 

 than it has for oxigen. " heat aUm^, 



Mr. Berthollet asserts, that, on calcining red oxide of by fierthollef, 

 iron in porcelain tubes, it gave out no portion of oxigen 

 when exposed to a powerful heat, though its colour appeared 

 to change from red to blackf. 



Fourcroy too asserts, that on calcining oxide of iron no Fowrcror, 

 oxigen was evolved ; but he pretty constantly obtained car- 

 bonic acid, when the oxide assumed a black colour*. 



Mr. Bucholz, in the paper alreariy quoted, observes, Br,cl:ol,£, 

 that red oxide of iron being exposed in Hessian crucible* 

 to the action of a powerful fire, the weight of the cruci-- 

 bles and oxide was diminished a few grains. Thi^ loss, 'if 



• Trait6 61cm: de Cbim. torn, I, p. 41. 

 t Jqucn, do Phys IfiOo, toI. II,^p. 5iiJ. 

 X MC-m.' et Ob». dV'Cbunr'p, 102, lOi. 



