60 
Iron . 
ty of malleable iron obtained is still less than in the two 
former : the surface of the metal being exposed by the 
removal of the scoria, oxydation takes immediate effect ; 
and whilst malleability is pervading the under surface of 
the metallic button, the upper one becomes reduced to a 
blackish blue oxyde. Here a striking proof is afford- 
ed of the great affinity which oxygen has, in high tem- 
peratures, to heat or caloric. Were the surface of such 
highly oxygenated crude iron exposed, while fluid, to at- 
mospheric ah, at an ordinary medium, for l-6th of the 
time, its whole metallic properties would be completely de- 
stroyed : in the present instance nearly one-half of the me- 
tal is preserved, although its surface is exposed to the ac- 
tion of a violent current of gas, (air) ignited to the highest 
pitch of whiteness^. In the proper assay of this ore I have 
* I have frequently observed, in experiments with pretty deep 
crucibles, where the most violent heats were excited, and where 
the fluid metal had assumed a whitish-blue colour somewhat inclin- 
ing to azure, that the quantity of oxyde formed was imperceptible, 
and never visible while the heat was continued of equal intensity ; 
when this agent became less urgent, the surface of the metal be- 
came oxydated as usual. When a regulus of crude iron thus ex- 
posed was wished to be obtained free from oxydation, a little dry 
charcoal was introduced into the crucible so as to cover the regu- 
lus ; this prevented the action of the air from taking effect while 
cooling, and preserved the button smooth. During such expo- 
sures, when no oxyde was produced, I have noted a loss of metallic 
parts equal to 5.7, or 10 per cent . when the space of time did not 
exceed one hour. Among several conjectures respecting the 
cause of this deficiency in weight, and real abstraction of metal, 
the two following have with me most weight. 1st, Either the me- 
tal deflagrates in small particles, which are thrown out of the cru- 
cible in sparkles, made invisible by the transcendent brightness of 
the surrounding heat i Or, 2d, that in consequence of the fluid me- 
tal being exposed to such a degree of heat, in contact with oxygen- 
ous gas, part of it becomes acidified, and forms the ferric acid,* 
* This acid has never yet been shewn. T. G. 
