in determinins: Gaseous Combination, 359 



'to 



upon which a stream of hydrogen was flowing. It became 

 incandescent considerably below visible redness, and con- 

 tinued so as long as hydrogen was supplied. 



The action of nickel differs, then, in no respect from that of 

 cobalt, but consists in a similar succession of oxidations and 

 reductions. It is therefore entirely distinct from that of pla- 

 tina and its congenera* ; yet nickel has been placed by Dobe- 

 reiner, MM. Dulong and Thenard, and Mitscherlich f , all 

 of whom observed its activity in the form of sponge, in the 

 same category with platina and the noble metals. 



§ V. Iron, 



1. The yellow oxalate of iron was heated in a closed retort 

 until carbonic acid was no longer liberated. The reduced 

 metal was pyrophoric when poured through the air. A por- 

 tion, carefully transferred from the retort to a platina dish, on 

 which a current of hydrogen was flowing, became incan- 

 descent without foreign heat ; and a circular ring of powder 

 nearest the aperture from which the gas issued, continued to 

 glow as long as hydrogen was produced. The oxide imme- 

 diately contiguous to this ignited circle was black, but the 

 remoter parts had passed into the state of red oxide and un- 

 derwent no further change. The incandescence continued for 

 many minutes, and at length became so vivid as to kindle 

 the jet of hydrogen J. 



After the experiment had terminated and the product been 

 allowed to cool, it appeared that the metal was entirely con- 

 verted into the state of oxide, and chiefly of red oxide. This 

 oxide was heated on a platina dish, and a stream of hydrogen 

 directed upon it. About the temperature of reduction it 

 became incandescent at the points of its surface where the 

 hydrogen impinged, and after the lapse of a few minutes in- 

 flamed the hydrogen. 



It appears, then, that iron, when recently reduced and in a 

 pulverulent state, does not induce the direct combination of 

 hydrogen with oxygen. Like the other oxidizable metals be- 

 fore enumerated, it causes the silent formation of water, only 



* " celle de faciliter par leur contact la combinaison des fluides 



elastiques sans s*unir a aucun de ces fluides ou de leurs composes." — 

 Thenard, torn. ii. p. 19. 6"™^ Edit. 



t Lehrbuch der Chemie, b. i. p. 226. 



X This experiment, as well as the second on cobalt, are liable to objec- 

 tion from the pyrophoric state of the metals, and are only introduced as 

 completing the series. Stromeyer has also called in question the perfect 

 reducibiliiy of oxide of iron by hydrogen, and is of opinion that the pyro- 

 phoric substance is the protoxide, and not the pure metal. 



