Ky 
[ 389 ] 
NATURAL 
On, the Nature of the Diamond. By 
Smithfon Tennant, E/q. F. R. 8. 
From the Philofophical Tranfaéions of 
the Royal Society of Lendon. 
IIR Ifaac Newton having ob- 
ferved that inflammable bodies 
had a greater refraction, in propor- 
tion to their denfity, than other 
bodies, and that the diamond re- 
fembled them in this property, 
was induced to conjecture that 
the diamond was of an inflam- 
mable nature. The inflammable 
fubftances which he employed 
were, camphire, oil of turpentine, 
oil of olives, and amber; _ thefe 
he called “ fat, fulphureous, unétu- 
ous bodies;” and, ufing the fame 
expreflion refpecting the diamond, 
he fays, it is probably “an unétu- 
ous body coagulated.”” This re- 
markable conjecture of Sir Ifaac 
Newton has been fince confirmed 
by repeated experiments. It was 
found that, though the diamond 
was capable of refifting the effects 
of a violent heat when the air was 
carefully excluded, yet that, on 
being expofed to the action of heat 
and air, it might be entirely con- 
fumed. But, as the fole obje& of 
thefe experiments was to afcertain 
the inflammable nature of the dia- 
HISTORY. 
mond, no attention was paid to the 
roduéts afforded by its combuftion ; 
and it ftill, therefore, remained to 
be determined, whether the dia- 
mond was a diftiné& fubftance, or 
one of the known inflammable 
bodies; nor was any attempt made 
to decide this queftion, till M. La- 
voifier, in 1772, undertook a feries 
of experiments: for this purpofe. 
He expofed the diamond to the 
heat produced by a large lens, and 
was thus enabled to burn it in clofe 
glafs-veffels. | He obferved, that 
the air in which the inflammation 
had taken place had become partly 
foluble in water, and precipitated 
from lime-water a white powder, 
which appeared to be chalk, being 
foluble in acids, with effervefcence. 
As M. Lavoifier feems to have had 
littke doubt that this precipitation 
was occafioned by the production 
of fixed air, fimilar to that which is 
afforded by calcareous fubftances, 
he might, as we know at prefent, 
have inferred that the diamond 
contained charcoal; but the rela- 
tion between that fubftance and 
fixed air was then too imperfectly 
underftood to juftify this conclufion, 
Though he obferved the refem- 
blance of charcoal to the diamond, 
yet he thought that nothing more 
could be réafonably deduced from 
b3 their 
. 
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