iJ* 03 
C H •£ M I S T R Y, 
ve of carbonic acid. to. There are fubftances which 
are in a (late of intermediary competition, between the 
diamond and charcoal. Thele are plumbago, or native 
■carbure of iron; incombultible foffil coal; the carbure 
of alumine of Dolomieu ; the anthracolite of Werner; 
the black matter united to iron in the (late of cad-iron 
and Heel; carbonaceous refiduums difficult to be incine¬ 
rated ; and carbon itfelf unburnt ( debrule ,) by the action 
■of a llrong heat without the contact of air. n. Thefe 
fubftances mixed, or weakly combined with three or four 
hundredths of their weight of iron, oralumine, give bytheir 
combuftion carbonic acid, like charcoal and the diamond. 
They approach to carbon by their colour, their lightnefs, 
their opacity ; by their ferving, like it, to decompofe wa¬ 
ter, to cement iron, to de.oxydate metals, to deoxygenate 
fulphur, phofphorus, and arfenic; and, by conducing, 
•like it, the eleftric fluid. They approach the diamond by 
containing more combuftible matter than charcoal; by 
abforbing alfo more oxygen, and producing more carbo¬ 
nic acid; by decompofing more nitrous acid ; by burn¬ 
ing only at a much higher temperature, even in nitre in 
fufion ; and by their combuftion being Hopped when this 
tegaperature is lowered. They feem to differ from each 
other by the property of producing with zinc galvanic 
irritation, as well as tilver does: which can be effefted 
.neither by the diamond nor charcoal. 
12. Thus the diamond is pure carbon, the pure acidi- 
fiable bale of the carbonic acid. Its combuftion is ef¬ 
fected in three periods, which require three different 
temperatures. At the firft, which is the higheft, the dia¬ 
mond afiumes a black leaden colour. It is an oxydation 
in the firft degree, the llate of plumbago and anthraco¬ 
lite. At the (econd temperature, which may be ellimated 
at eighteen or twenty pyrometric degrees, there is a fe- 
cond flow and fucceflive combination of oxygen. It is a 
progrefs of oxydation which conftitutes the habitual Hate 
of charcoal, or rather that in which it is found after tha 
aftion of a llrong heat in dole veflels has difengaged a 
part of its oxygen. Thus plumbago is an oxyd of the 
firft degree, charcoal an oxyd in the lecond, and the car¬ 
bonic acid the produft of the complete oxygenation of 
the carbon. Suppofing, then, that we operate with fuf¬ 
ficient precifion to take away from the furface of the dia¬ 
mond the black matter in proportion as it is formed, by 
fuddenly withdrawing from it each time the aftion of the 
folar fire, we lliould doubtlefs be able to convert it into 
charcoal, or at lead plumbago, if the too rapid paffage of 
the lalt degree of oxydation to oxygenation did not pre¬ 
vent us from furprifing it in that Hate. 13. In the lad 
place, feveral confequences, of importance to chemiftry 
and the arts, arife from thele principles. It will be alked, 
no doubt, how it happens that the Ample matter, pure 
carbon, the diamond, is fo rare, while its compounds in 
different Hates are fo abundantly diifufed ? To put an 
end to the altonilhment of thofe who might entertain any 
miftruft, I (hall oblerve, that aluminous earth is alfo one 
of the mod common matters, and that adamantine (par, 
as rare as the diamond, is, however, only alumine; that 
iron every where exilts, under all forms, except in the 
ftate of purity : the exiltence of native iron is Hill doubt¬ 
ful. The wonder exills only in the oppofition of fafts to 
our opinions, and will difappear in proportion as we dif- 
cover, and appropriate to ourftlves, the means employed 
by nature in producing the fame effefts. 
The Angularity and importance of thefe two experi¬ 
ments, fuggefted the idea of fearching for a confirmation 
of a new kind, by trying to make loft iron pafs to the 
ftate of Heel, by cementation with the diamond. 
It has hitherto been confidered as certain, that iron 
does not melt but by palling to the ftate of Heel or call- 
iron. But in what llate does the carbon enter into that 
combination ? It might be conje&ured, that it is in the 
ftate of plumbago, or oxyd of the firft degree; fince.that 
which is feparated by acids, exhibits the brilliant black- 
aefs and iocopabullibility which form its principal cha- 
1 
rafters. Hence fome were inclined to conclude, that the 
carbon entered into this union in the ftate of an oxydule ; 
that confequentiy the carbon employed in the cementa¬ 
tion of Heel began by deoxydating itfelf to a certain de¬ 
gree. This was even, in fome meafure, proved; as the 
carbon employed for this operation was indeed found to 
have a more brilliant afpeft, and nearly refilled 1 incinera¬ 
tion, like carbon in a mafs burnt in clofe veflels. But, if 
carbon really burns in the cementation of iron, it ought 
to dilengage from it oxygen gas. This is a queltion which 
I have endeavoured to refolve by experiment. 
I cemented fmall bits of iron in a porcelain retort, w r hich, 
in the preceding operation, had received a vitreous coat¬ 
ing, and which confequentiy was no longer permeable to 
air. Thefe fragments were all furrounded, on every fide, 
by charcoal of beech pulverized, and very dry. The re¬ 
tort was put into the reverberating furnace, and a tube 
connected to it and carried under a receiver filled with 
mercury. There was difengaged a quantity of elaftic 
fluid, compofed of carbonated hydrogen gas, and carbo¬ 
nic acid gas, the lalt of which was at firft only o - i 1 in 
bulk; towards the middle of the experiment, o - i3; and 
at the end, 0*15. 
The converlion of iron into Heel being found only lit¬ 
tle advanced, after three hours and a half expofure to the 
fire, we put the fame iron and the fame carbon again into 
the retort, and expofed it to the heat of a three-blaft fur¬ 
nace. This time there was only a very fmall quantity of 
gas; but it was Hill carbonated hydrogenous gas mixed 
with carbonic acid gas, and always with the fame pro- 
greflion of the latter; which made at firft only 0^07 of 
volume, while the lalt portions contained 0-12. The iron, 
on this occafion, was converted into Heel, and even the 
fragments had united by a commencement of fufion. 
It Was very probable that a part of the carbonic acid, 
collected in this operation, might have been formed at 
the expence of the remaining carbon and with difengaged 
oxygen; but the conftant prefence of the hydrogen only 
ferved to indicate the difficulty of freeing the carbon en¬ 
tirely from the lad portion of water it contained. I lhall 
here take occafion to obferve, that this experiment feems 
not at all reconcileablc with the opinion of lome chemifts, 
that hydrogen has more affinity than carbon for oxygen: 
an opinion which they found on this circumftance, that 
carbon is precipitated, in Volta’s eudiometer, when a mix¬ 
ture of oxygen gas and carbonated hydrogen gas is mads 
to detonate, if a quantity of oxygen fufficient to acidity 
the two bafes has not been employed. I fay, that this 
affinity was not exerted in my experiment*: for it cannot 
be doubted that the temperature was high enough to re¬ 
produce water by the union of the oxygen and hydro¬ 
gen ; and we can here fee nothing which could decide a 
preference of the oxygen for the carbon. 
Thefe confiderations feemed to me fufficient to create 
a new intereft in regard to this experiment, propofed by 
C. Clouet. I did not hefitate, therefore, to employ in it 
one of the diamonds preferved in the cabinet of the Poly¬ 
technic School, according to the leave granted by the 
council; being perfuaded that if it difappeared in the 
operation, merely by expofure to a high temperature, in 
contaft with iron, without the acceffion of the air, or any 
other oxygenating fubftance, the faft thereby eltablilhed 
would leave no room to regret having facrificed if. Clouet 
had himleif prepared a fmall crucible of foft iron, forged 
on purpofe out of picked heads of nails. Its form was 
a folid of eight planes, as Ihewn at fig. 4. It was (hut by 
a Hopper of the fame iron well adjulted, as at fig. 5. 
This crucible was to be placed in a Heflian crucible, 
furnilhed with a cover well luted. This was all the ap¬ 
paratus for the experiment. I cannot give a better idea 
of the refult, than by the report drawn up by C. Clouet, 
Welter, and Hachette. 
The diamond employed weighed 907 milligrammes. As 
it did not entirely occupy the crucible, we filled it with 
filings of the fame iron as that of which it was formed. 
The 
