C H E M 
In regard to the firft confideration, it will be fufficient 
for me to call to mind with what difficulty the commence¬ 
ment of a com l pofition of azot and oxygen is formed by 
the direct way, and the high degree of temperature which 
it requires, while nitrous gas cannot be in contact with 
oxygen without palling immediately to the acid ftate. 
Charcoal will then be to the carbonic acid, what nitrous 
gas is to the nitric; and the diamond will be to char¬ 
coal, what azot is to nitrous gas. There will, therefore, 
be no longer occalion of wonder that more oxygen is ne- 
ceflary to that fubftance, which as yet has none of it, than 
to that which has already been united with'the quantity 
necelfary for arriving at the firft point of faturation. 
The fecond conlideration refts on fafts no lefs conclu- 
five. Plumbago is a carbonaceous combuftible, which 
does not burn but at a very high temperature, or in ni¬ 
tre in fufion ; which produces by its combuftion carbonic 
acid; which, as well as the diamond, is^ more abundant 
in combuftible matter than carbon itfelf. We are in¬ 
debted to the illuftrious Scheele for the firft obfervation 
of this fa6l. One part of carbon alcalizes only five parts 
of nitre ; one part of plumbago can alcalize ten. The 
operation performed in a retort on eighty centigrammes 
of plumbago, gave him 357 cubic centimeters of carbo¬ 
nic acid gas. This agreement will not be contefted by 
thofe who, having been witnefles of our experiment, fo 
unanimoufly declared, that the furface of the diamond af- 
fumed inftantaneoully a leaden colour. 
This mineral is not the only body which prefents thefe 
ftriking charafters of a fubftance almoft incombuftible, 
and yet very abundant, in combuftible matter. I de- 
fcribed, fixteen years ago, in the Memoirs of the Aca¬ 
demy of Dijon, a foffil found in a mafs in the coal-pits 
of the Rive-de-Gier, which was fent to me under the 
name o f incombuftible coal, and which I then coniidered as 
real coal which had palled to the ftate of plumbago. I 
characterized it in that manner. Dolomieu has delcribed 
a foffil of the fame kind, which he calls carbure of alu¬ 
mine, which is the anthracolite of Werner. I iiad already 
fuipe&ed that it was neither the prefence of four or five 
centiemes of alumine, nor that of a ftill fmaller quantity 
of iron, that rendered it incombuftible, but the little ad¬ 
vanced ftate of the oxydation of the carbon. I fubjeCted. 
it to two experiments, by which this was fully confirmed. 
The objeft of the firft was to determine if the alumine 
prefent was in a ftate of combination fufficiently intimate 
to refill the aftion of potalh by the humid way : 100 parts, 
put in digeltion in that folvent, left it in 4-6 of alumine. 
The fecond was, to afcertain whether this combuftible, 
which poflefled fo little inflammability, had alfo the power 
to alcalize more nitre than carbon, confequently to take 
up more oxygen. Three fucceffive trials gave for a mean 
refult the alcalization of 7^87 parts of nitre by one part 
of that mineral; and the fame coally matter, digefted for 
four or five days in oxygenated muriatic acid, burnt com¬ 
pletely with 6-’5 of nitre. 
M. Klaproth, the celebrated chemift of Berlin, had be¬ 
fore fubmitted to trials of the fame kind a foffil delcribed 
by M. Widenmann, under the name of incombuftible coal, 
and found that 100 parts left, after combuftion at a very 
firong heat, only feven of a cineritious refiduum; that 
treated in a crucible with eight parts of nitre, and the 
mafs diffolved in water, acids occafioned no precipitate. 
Kirwan, in his experiments on coal, remarks, that that 
which he calls Kilkenny coal, having a metallic brilliancy, 
which does not burn but when carried to incandefcence, 
and which then confumes (lowly without emitting flame, 
can decompofe 9*6 of nitre. After this, I do not lee how 
there can remain any doubt, that thefe fuppofed incom¬ 
buftible fubftances are real oxyds of carbon, which, like 
coal or charcoal, have the property of conducing the 
eleCtric fluid ; of cementing iron ; of taking the oxygen 
from fome acidifiable bafes; but which are not at that 
degree of oxydation necelfary for exerdfing this feparat- 
ing affinity at a weak temperature. 
S T R Y. 39.1 
I mull not omit this opportunity of making fome ap¬ 
plication of this principle, which may become ufeful to 
the arts. It has not yet been fufficiently explained, why 
fome animal and vegetable matters produce carbon lo 
difficult to be incinerated; why charred pit-coal, known 
under the name of coke, or cinders, and which has been 
half burnt in the preparation, is, however, fo powerful a 
combuftible ; why peat, or turf, the weakelt of combul- 
tibles, acquires, by being charred, the property of weld¬ 
ing large pieces of iron better than charcoal; and why, 
in the laft place, charcoal, when expofed to a very ftrong 
heat in veflels impenetrable to air, becomes there, in a 
certain degree, incombuftible, as is proved in experiments 
made by Mr. Tennant. 
The anfwer to all thefe queftions may be found in the 
theory I have laid down: they are charcoals in the firft 
degree of oxydation. Thus lome of them have not yet 
acquired that which conftitutes charcoal.properly fo call¬ 
ed; others, after pofieffing all the qualities of vegetable 
and mineral carbon, have returned to the firft degree by 
a real unburning ( debrulemen1) of the remaining carbon ; 
fo that, by ^lofing their inflammability, they become ca¬ 
pable of fixing a greater quantity of oxygen, and confe¬ 
quently of fetting at liberty a greater quantity of caloric, 
when they find themfelves at a temperature fufficiently 
high to determine and complete their acidification. 
Some practical conlequences will doubtlefs hence be 
deduced, in regard to procefles for the reduction of me¬ 
tals ; for the ce/nentation of fteel, which it is probable 
takes up only oxyd of carbon, fince it is feparated from 
it in that ftate ; for the incineration of the carbonaceous 
refiduums of our analyfis ; for the carbonization of wood, 
pit-coal, and turf: in a word, we may, perhaps, thence 
conclude the poffibility of rendering ufeful thofe mafles 
of pit-coal, laid to be-incombuftible, found at Rive-de- 
Gier, by mixing it with more inflammable matters, to 
maintain the temperature which determines its combuf¬ 
tion. Its pofition, texture, and all its exterior charac¬ 
ters, announce, as already faid, that it conlifcs of beds of 
coal changed by a fubterranean fire ; and this is confirmed 
by tradition, which preferved to that mountain, for three 
centuries, the name of the Mountain of Fire, (Montague de 
Feu.) We can now pronounce, that it is coke too far ad¬ 
vanced, but fo much the more fufceptible of producing a 
great heat, under favourable circumftances. 
Racapitulation. —I (hall here enumerate the confe- 
quences, or rather the faCls, which refult from the pheno¬ 
mena obferved in the two combuftions of the diamond by 
the folar fire, and the experiments which followed. 1. It 
is not only by the colour, weight, hardnefs, tranfparency, 
and other fenfible characters, that the diamond differs 
from charcoal, as feems hitherto to have been believed 
2. Nor is it by the ftate alone of the aggregation of the 
matter, that conftitutes diamond : 3. Neither is it on ac¬ 
count of the two hundredth part of the cineritious refiduum 
left by carbon, or the fmall quantity of hydrogen which 
it contains. 4. It is more eflentiaily by its chemical pro¬ 
perties that it differs. 5. The diamond is the pure com¬ 
buftible fubftance of this genus. 6. The product of its 
combuftion, or of its combination with oxygen to fatura¬ 
tion, is carbonic acid without refidue. 7. Carbon burns 
at a temperature eltimated at 188 0 of the centigrade ther¬ 
mometer; the diamond does not inflame but at about 
thirty pyrometric degrees, which, according to Wedg¬ 
wood’s icale, makes a difference of 188 to 2765. 8. Char¬ 
coal, when kindled, maintains of itfelf, in oxygen gas, 
the temperature necelfary for its combuftion. The com¬ 
buftion of the diamond Hops when you ceafe to maintain 
it by a furnace-heat, or the union of the folar rays. 9. 
The diamond, for its complete combuftion, requires a 
much greater quantity of oxygen than charcoal does, 
and produces alfo more carbonic acid. One part of char¬ 
coal abforbs, in this operation, 2527 of oxygen, and pro¬ 
duces 3*575 of carbonic acid. One of diamond abforbs 
a little more than four of oxygen, and really produces 
five 
