A New and Curious variety of Combustion. ~389 
tina, with an equality of surface. Ten grammes of iron wire 
_ issufficient to decompose, within a few hundredths, a pretty 
rapid current of ammoniacal gas, kept up during eight or ten 
hours, without the temperature passing the limit at which 
the ammonia resists decomposition. Three times the quan- 
tity of platina wire produces far less effect, even at a high- 
er heat. . 
These remarkable results depend, perhaps, on the same 
causes as those which occasion gold and silver to effect the 
combination of oxygen and hydrogen at 300°, platina in 
mass at 270°, and platina in sponge at common tempera- 
tures. Now, if it is observed, that iron which decomposes 
ammonia so readily, effects with somuch difficulty the union 
nia, we are induced to believe that among the gases, 
some tend to unite under the influence of metals, while oth- 
ers tend to separate, and that this property varies aceerding 
to the nature of each. ‘Those of the metals which produc 
one of these effects produce the other only in a very small 
degree. Ann, de Chimie, Jug. 1823. - 
In the original paper of Dobereiner, (translated.in Til- 
loch’s Mag. for Octob.) he remarks, “* What useful applica- 
tions of this discovery may be made in Oxymetry, the syn- 
thesis of water, &c. I shall hereafter state more cireum- 
stantially. I shall at present merely observe, that the en- 
tire phenomenon must be considered as an electric one, 
that the hydrogén and platinum form a Voltaic combina- 
tion, in which the former represents the Zinc ;—the first es- 
tablished instance of an electric alternation formed by an 
elastic fluid, and a solid substance, the application of which ~ 
will lead to further discoveries.’ is 
In another letter, dated Aug. 3d, 1823, he says, “ If hy- 
drogen gas be suffered to issue from a Gazometer through a 
Capillary tube bent downwards, upon the platinum con- 
tained in a small glass funnel, sealed at the bottom, so that 
the stream may mix with the atmospheric air before it comes 
in contact with the platinum, which is effected when the 
tube is from 1 to 11 or 2 inches distant from the platinum, 
the latter becomes almost instantly red, and white hot, and 
remains so, as long as the hydrogen continues to flow 
