on the Combuftion of the Diamond. PEAR | 
11. Thefe fubftances mixed, or weakly combined with 
three or four hundredths of their weight of iron, or alumine, 
give by their combuttion carbonic acid, like charcoal and the 
diamond. é 
They approach to carbon by their colour, their lightnefs, 
their opacity; by their ferving, like it, 1o decompofe water, 
to cement iron, to deoxydate metals, to deoxygenate ful- 
phur, phofphorus, and arfentc; and by conduéting, like it, 
‘the eleGtric fluid. They approach the diamond by contain- 
ing more combuftible matter than charcoal; by abforbing 
alfo more oxygen, and producing more carbonic acid; by 
decompofing more nitrous acid; by burning only at a much 
higher, temperature, even in nitre in fufion; and by their 
combuftion being ftopped when this temperature is lowered. 
They feem to differ from each other by the property of pro- 
ducing with zine galvanic irritation, as well as filver does : 
which can be effected neither by the diamond nor charcoal. 
12. Thus the diamond is pure carbon, the pure acidifi- 
able bafe of the carbonic acid. Its combuftion is effected in 
three periods, which require three different temperatures. At 
the firft, which is the higheft, the diamond affumes a black 
leaden colour. It is an oxydation in the firft degree, the ftate 
of plumbago and anthracolite. At the fecond temperature, 
which may be eftimated at 18 or 20 pyrometric degrees, 
there is a fecond flow and fucceflive combination of oxygen. 
It is a progrefs of oxydation which conftitutes the habitual 
ftate of charcoal, or rather that in which it is found after 
the action of a flrong heat in clofe veffels has difengaged a 
part of its oxygen. 
Thus plumbago is an oxyd of the firft degree, charcoal an 
oxyd in the fecond, and the carbonic acid the produét of the 
complete oxygenation of the carbon. 
Suppofing, then, that we operate with fufficient precifion 
to take away from the furface of the diamond the black mat- 
ter in proportion as it is formed, by fuddenly withdrawing 
from it each time the action of the folar fire, we fhould doubt- 
lefs be able to convert it into charcoal, or at leaft plumbago, 
if the too rapid paffage of the laft degree of oxydation to oxy- 
genation did not prevent us from furprifing it in that ftate. 
; Bb2 13. In 
