DIAMOND. 
fiiamond. The same results were obtained 
on heating the diamond in a glass vessel 
containing common air placed over quick- 
silver. Lavoisier drew the conclusion, that 
the diamond is a combustible body ; and 
that as objects of chemistry there exist a 
great analogy between it and charcoal. 
Some years afterwards Guyton shewed 
that the diamond is consumed when heated 
with the nitrate of potassa, and aflFords car- 
bonic acid. This experiment was repeated 
with more precision by Mr. Tenant. He 
exposed to a strong red heat, for an hour 
and a half in a gold tube, two grains and a 
half of small diamonds with a quarter of an 
ounce of nitrate of potassa. The salt was 
decomposed, and on examining the residu- 
um, the potassa was found to have attracted 
carbonic acid, while the diamonds were 
entirely consumed. The quantity of carbo- 
nic acid was attempted to be ascertained, 
by adding to the solution of the residuum in 
water a solution of muriate of lime, a preci- 
pitate of carbonate of lime was formed ; 
from this the carbonic acid was disengaged 
by muriatic acid, and it occupied a space 
equal to about 10.1 ounce measures of 
water. This, according to Mr. Tenant’s 
calculation, was about the quantity that 
ought to have been obtained from two 
grains, and a half of charcoal combined 
with oxygen ; and he therefore concluded 
that the diamond is charcoal, and differs 
from that substance only in its crystallized 
form. 
Guyton at length investigated the subject 
with diat precision which was necessary to 
fix our opinion as to the nature of the dia- 
mond. The diamond, an imperfect octa- 
hedron, was placed on a small porcelain 
crucible, elevated in ajar filled with oxygen 
gas, ascertained to be pure, placed over 
mercury. The concentrated solar rays 
were thrown on the diamond by a large 
lens : it appeared at first farinaiceous, and 
was afterwards sensibly blackened on its 
surface : the appearance of combustion was 
extremely faint, and when it had begun did 
not continue if the solar heat was with- 
drawn. Afterwards, when a more power- 
ful lens was employed, the combustion was 
more evident; the diamond first became 
black, and of a coally appearance ; an in- 
stant after it became brilliant, and at some 
points it appeared to boil ; it gradually di- 
minished, and the application of the solar 
heat was repeated at different times until 
it was entirely consumed. The quantity of 
carbonic acid which had been formed was 
ascertained by introducing a solution of ba- 
rytes in water, and the unexpected result 
obtained, that the quantity was much 
greater than what would have been formed 
by the combustion of the same weight of 
charcoal as of diamond. Twenty-eight 
pans of charcoal in burning combine with 
72 of oxygen, and from 100 of carbonic 
acid; while the same weight of acid, ac- 
cording to Guyton’s experiment, is formed 
from the combustion of 17.88 of diamond, 
which combine therefore w'ith 82.12 of 
oxygen. Guyton concluded, therefore, that 
it is not merely by its colour, weight, hard- 
ness, transparency, and other sensible qua- 
lities, that the diamond differs from char- 
coal ; neither does the difference depend on 
the state of aggregation, nor are the distinc- 
tive properties of charcoal owing to tlie 
two hundredth part of residue which it 
leaves in the form of ashes, or to the small 
quantity of hydrogen which it may contain ; 
but to its oxydation, diamond being the 
simple base of which charcoal is the oxide. 
A striking fact with regard to the oxyge- 
nizement of the diamond is the high tempe- 
rature which is requisite to its taking place. 
It appears from Guyton’s statement, to be 
charred at about the temperature of 18 or 
20 of Wedgwood’s scale, (3417 or 3677 of 
Frahenheit’s) and at about 30 (4977°) it 
burns with a feeble flame ; nor does it even 
in oxygen gas produce as much heat as to 
support its own combustion. This is no 
doubt owing to tlie very strong cohesion 
fexerted between its particles. (Memoir 
by Guyton, Annales de Chimie, t. 31.; or 
Abstract of it in Nicholson's Journal, 4to. 
viii. p. 298.) 
The appearances attending the combus- 
tion of the diamond have been observed 
with perhaps more accuracy by Sir George 
Mackenzie ; and the temperature requisite 
has been stated by him as less high. A 
diamond cut and polished, when introduced 
into a muffle previously heated red hot, soon 
acquired the same redness as the muffle, 
but in a few minutes more became distin- 
guished by a bright glow, and began to con- 
sume. A piece of plumbago placed beside 
it exliibited a similar luminous appearance, 
but it began at a lower temperature. When 
the air was excluded from the muffle, both 
lost their brightness, but it returned on the 
admission of the air, and was much in- 
creased by blowing on them writii a bellows. 
To ascertain at what temperature the com- 
bustion of the diamond took place, one of 
the pyrometrical pieces of Wedgwood was 
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