IMPROVEMENTS IN OBTAINING AND APPLYING CRYSTALLINE AND OTHER FORMS OF CARBON
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by James Mactear at the Office of the
Commissioners of Patents on the 6th January 1880.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN OBTAINING AND APPLYING CRYSTALLINE AND OTHER FORMS OF
CARBON."
This Invention comprises developments or modifications, extensions, and appli-
cations of the process or processes described in the Provisional Specification relative
to an application for Letters Patent lodged by the present applicant on the 16th
December 1879 (No. 5143).
In carrying out one part of the present Invention any suitable carbon compound
or a mixture of one or more carbon compounds with or without free carbon is
treated so as to effect dissociation or separation of the carbon under conditions
favoring its assumption of a state of great density. The object is accomplished by
applying considerable pressure and heat, it being in some cases necessary for the
carbon compound or mixture to be in presence of some other substance or
substances which or part of which will combine with what is separated from the
carbon. In some cases the carbon set free in the reaction is found partly in a
crystalline condition, and partly in other forms of various densities and hardness
and it is partly colorless and partly colored. It will probably be found possible to
modify or regulate the details of the operation so as to obtain the larger part of
the separated carbon in that one of its forms which may be desired in each case.
Thus in one case the product may be principally in the form of the variety of
graphite known as plumbago or black-lead, and be suitable for making pencils and
the like, also for making anti-frictional compounds such as metaline and also for
other important uses. In another case the principal product may be in a diamond-
like or other form having a hardness equal or possibly even superior to that of
some natural diamonds, such hardness rendering the carbon extremely useful and
valuable in many operations in the arts, whilst its comparatively moderate cost
will admit of its use in many applications from which natural diamonds have been
hitherto excluded by their costliness.
In carrying out the Invention it is preferred to employ a compound of carbon
containing oxygen or hydrogen or both oxygen and hydrogen. In one modification
carbonic anhydride is used, and sodium bicarbonate is employed as its source,
whilst a suitable oxidisable metal, such as iron (by preference in a finely divided

page_text: state and as reduced by means of hydrogen) is provided to take up the oxygen
dissociated from the carbonic anhydride. In a second modification oxalic acid and
iron or other suitable oxidisable metal are employed. Oxalic acid is known to be
separable by heat into carbonic anhydride, carbonic oxide, and water, and it is
probable such separation takes place at the earlier stage or stages of the operation,
the carbon and oxygen being subsequently separated from each other. In a third
modification benzene or other suitable compound of carbon and hydrogen is taken
and is acted on in presence of chlorate of potash or other substance which on the
application of heat will yield oxygen to combine with the hydrogen separated from
the carbon.
The mixture or combination of substances made up according to any of the
modifications herein before described is confined in a vessel of sufficient strength
made of steel or other material which will not by reason of its chemical nature
interfere with the reaction; and the vessel having been closed with a screw plug
or in any other sufficient manner is subjected to heat. A temperature between
300 and 400 degrees centigrade has been found sufficient in practice, and it has been
found that about seventy hours are sufficient for the duration of the operation,
including the cooling; but these quantities may possibly be capable of modification
with advantage, particularly if different compounds are employed or if different
forms of carbon are required. The pressure employed may be that due to the
action of the heat on the confined substances, but a less pressure may be found
sufficient with a higher temperature, or a lower temperature with a greater
pressure.
The crystalline or hard carbon produced according to the present Invention, and
obtained in the form of small crystals or grains or subsequently reduced to smaller
grains, and which may be termed carbon or diamond sand or dust may be applied
in various ways for grinding, abrading, or cutting. Thus the carbon or diamond
sand or dust may be substituted for emery in the formation of grinding or cutting
surfaces, being for that purpose partially embedded in or otherwise applied to
metallic or other suitable surfaces, or being combined with vitreous or other
cementing substances, and the compound being shaped into grinding wheels or
other tools.