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XIII. On the Atomic Weight of Graphite. By B. C. Brodie, F.B.8., Professor of 
Chemistry in the University of Oxford, and President of the Chemical Society. 
Eeceived May 12, — Eead May 12, 1859. 
The term Graphite has been indiscriminately applied to many varieties of native carbon 
of very different properties. The graphite of New Brunswick differs but little in 
appearance from anthracite coal. The graphite of Greenland is not very dissimilar, but 
possesses rather more metallic lustre. However, among these varieties of carbon, two 
may be especially distinguished, — ^by a superior degree of metallic lustre, by their struc- 
ture, and other well-defined properties. In the following paper, the term Graphite is 
limited to these two varieties, which may be further distinguished as “ lamellar” and 
“ amorphous.” 
The lamellar graphite is found in great abundance in Ceylon, whence large quantities 
are annually imported into this country. It appears in commerce in masses, some- 
times of the weight of many pounds, of a brilliant metallic lustre, and possessing a 
distinct fibrous structure. It is very difficult by mechanical processes to bring this gra- 
phite to a fine state of division ; however, by a prolonged grinding in water, it may be 
reduced to minute fiat plates. This graphite is associated with quartz. A deposit of 
the same variety of graphite has recently been discovered at Travancore. The graphite 
from Travancore has no fibrous structure, but is in the form of slightly coherent, minute 
plates. Specimens of a similar graphite have also been given to me, from Moreton Bay 
in Australia, in a matrix of quartz, and from Ticonderoga, in the State of New York, 
associated with olhine and sphene. When cast iron is dissolved in acid, a residue is 
left of about 4 per cent, of carbon in the form of graphite. This graphite also consists 
of minute brilliant plates, and is perfectly similar in its appearance and properties to 
the lamellar variety of native carbon. Amorphous graphite is found in Borrowdale in 
Cumberland, and is also largely imported into this country from Germany, probably 
from Griesbach near Passau, but I am unable to speak with certainty as to the locality 
whence it comes. It appears as a powder of a silvery grey colour, soft to the touch, and 
which rubbed on paper gives a brilhant metallic streak. This graphite is much softer 
than the other variety, and therefore better adapted for the manufacture of pencils. 
The graphite used in my experiments was in all cases carefully purified by boiling 
with acids, and by fusion with hydrate of potash in a silver crucible ; unless otherwise 
mentioned, it is to be understood to be the variety from Ceylon. The graphite thus pre- 
pared leaves an almost inappreciable residue, and gave to analysis 99*96 of carbon. Its 
specific gravity was ascertained in two determinations as 2*25 and 2*26. 
The following investigation was undertaken with the view of ascertaining the weight 
