150 
THE TROPICAL AGRICULTURIST. 
[Sept. 1, 1899. 
fluot of the Ceylon mines is crystalline, of great 
purity, analysing in some instances over 99 per cent, 
carbon, while that of the Borrowdale mines is 
amorphous and also very pure. 
The chief impurity in graphites iron ; indeed, its 
constant presence and frequent large quantity led 
to the belief, in the early days, that graphite 
was a carbon-iron compound, and it was even 
sometimes called carburet of iron. 
Uses. 
It is quite probable that the first use made of 
graphite was an instrument for writing. The first 
aoconnt we have of its employment for this purpose 
ia contained in the writings of Conrad Geasner on 
" Cosails," published in 1565. A picture of a pencil 
is shown, and, referring to it, he says: — "The pencil 
represented below is made for writing, of a certain 
kind of lead (which I am told is an artificial sub- 
stance termed by some, English antimony), 
Bharpened to a point and inserted in a wooden 
handle" (Roscoe). This pencil was probably made 
of graphite from the Borrowdale mines, which, we are 
told, were in operation in the sixteenth century. 
Ita uses for other purposes than pencils are of 
much more recent date, probably all of them 
falling within the present century, and nearly all 
within the last few years. 
The present uses of graphite include the manu- 
facture of pencils crucibles, stove polish foundry 
facing, paint, mortar and dynamo bushes, ant- 
friction compounds, electrodes for electro-metallur- 
gical work, conducting surfaces in electro-typing, 
• and covering the surface of powder grains. For 
most of these purpose it is used in the natural impure 
• state, while for others it is necessary to render it 
quite pure and free from grit. Its purification is accom- 
■ plished by a method worked out by Brodie, which 
consists in first grinding, or otherwise reducing the 
graphite to a state of fine subdivision, washing out 
the heavier impurities, mixing 14 parts with 1 part of 
potassium chlorate and 2 parts of concentrated sul- 
phuric acid, heating on a water-bath for some hours, 
washing thoroughly and afterwards roasting at a red 
heat. If silica is present a treatment with hydrofluoric 
acid is added to the process. 
The mining and manufacture of graphite into 
articles for which it has been found useful give em- 
ployment to thousands of people. The mines of 
Ceylon alone, when working to their capacity, em- 
ploy about 24,000 men, women, and children ; the 
work, however, is done entirely by hand, and in a very 
crude manner (Watts' " Diet, of Chem.," 1890). In 
the city of Nuremburg, Germany, the home of the 
famous Faber pencil, are twenty-six factories, 
employing about 5,508 people in the making of pencils 
("End. Brit."). 
3Ianufacture. 
The rapid increase in the use graphite, and con- 
sequent decrease in Nature's stocks, make the pro- 
blem of manufacturing it to order a subject of much 
Importance. 
When we consider the hundreds of thousands of 
chemical changes men are constantly putting the 
elementary bodies through, and the very prominent 
part taken by carbon in these re-actions, it would 
be rather remarkable if at some point. Nature's 
method for producing graphite was not discovered. 
That it is not a very difficult act is evident from 
the fact that it has been accomplished, in a small 
way, in several instances. 
Mr. Muir, in Watt's " Dictionary of Chemistsy," 
edition of 1890, mentions six recognised methods. 
(1) By heating charcoal with molten iron, and dis- 
solving out the iron with hydrochloric and nitric acids. 
(2) By the slow decomposition of hydrocyanic 
acid and boiling the product with nitric acid. 
(3) By evaporating the mother-liquors obtained in 
making soda: these contain cyanogen compounds 
which are decomposed at a certain concentration of 
the liquid with formation of ammonia and graphite, 
(4) By leading carbon monoxide over ferric 
oxide at 300O to 400O, , 
(5) By the de-composition of carbon disulphide 
Bit nigh temperature, ia contact with metallic iron. 
(6) By leading carbon tetrachloride over molten 
pig iron. 
Whether or not any of these methods could be 
developed to a state providing a commercial process, 
I am not prepared to say, but am inclined to think 
not. They have always been considered accidents or 
chemical feats of the laboratory, and in some ins- 
tances their formation was very objectionable. 
The Cowles Bros., of Cleveland, O., are reported to 
have found that graphite sometimes occurred in or 
about the charge of an electric furnace. This for- 
mation is referred to in one of their patents, and a 
feature of the patent is a provision to get rid of the 
material, as it was very objectionable on account of 
its high electric conductivity. Its formation was 
not reduced to a method, the causes for, or the 
exact conditions under which it was made, not 
having been investigated. It was like some of those 
in the list of Muir, an accident, and a great 
nuisance. 
Still another way of making graphite was described 
by G. Rose, in 1872. He exposed a cut diamond, bedded 
in charcoal, to a temperature equal to molten cast 
iron, whereupon the surface became coated with 
graphite. It is safe to say this process will never 
attain commercial success nor popularity. 
Finally, in the " Encyclopsedia Britanica ' (1890) we 
are told that by heating to the high temperature 
afforded by a powerful galvanic battery, both the 
diamond and amorphous carbon are converted into 
graphite." This statement I will refer to later on. 
In a paper which I had the honour of presenting 
to the institute at its stated meeting of June 21, 
1893 ("Carborundum: its History, Manufacture, and 
Uses"), reference was made to the formation of a 
black material consisting of a mixture of carborun- 
dum and free carbon during the operation of the 
carborundum furnaces. This was again referred to, 
and at much greater length, by Mr. Francis A. Fitz- 
gerald, chemist to the Carborundum Company, in a 
lecture delivered before the Institute on December 
lltb, 1896 ("The manufacture and Development of 
Carborundum at Niagara Falls"), aftfer it had been the 
subject of much thought and study, and when I had 
about concluded the formation of a theory covering 
the transformation of amorphous into graphitic carbon. 
Very early in my experiments on the manufacture 
of carbonundum, I noticed that graphite occasijnally 
formed in the portion of the furnace charge lying 
next to the cylinder of granular amorphous carbon 
which passed through the centre of the furrace and 
which became heated to an extremely high tempera- 
ture, by the passige of a heavy electric current, and 
around which the charge was placed to receive the 
heat necessary for the formation of carborundum. 
Also that when ordinary bituminous coal coke was 
used to form the core, quite a large amount of it 
was converted into graphite, whereas, when petrols utn 
coak was used, very little of it was made graphite. 
By a careful study of these formations, it was found 
that the graphite formed outside of an surrounding 
the core was produced by the decomposition of the 
carborundum, which is chemically, a carbide of 
silicon, and by induction from a number of known 
facts, that that form within the core was also prodficed 
from a similar decomposition of carbides, which were 
created by the chemical union of the carbon of the 
core with its contained impurities. The facts from 
which I have drawn this conclusion are : — 
1. Comparatively pure petroleum coke produces 
practically no graphite. 
2. Impure bituminous coal coke produces large 
quantities. 
3. The larger the known percentage of impurities 
in the bi'umious coal coke, the greater the amount 
produced. 
4. That only a part of the carbon of the core ia 
converted into graphite. This not being increased, 
even by repeated use of the same grains, in successive 
carborundum furnaces. 
The graphite found by the destruction of carborun- 
dum is remarkable in that it retains the form of the 
crystal of carborundum, from which it is, derived. It 
has, however, less than one-third the weight of car- 
