Improvements in the Treatment or Purification of Graphite to Render it Suitable for Industrial Purposes.
Year: 1891

page_text: Date of Application, 11th June, 1891
Complete Specification Left, 8th Mar., 1892-Accepted, 21st May, 1892
PROVISIONAL SPECIFICATION.
Improvements in the Treatment or Purification of Graphite to Render
it Suitable for Industrial Purposes.
I, WILLIAM Luzi, Chemist, of 18, Hospitalstrasse, Leipzig, in the Kingdom of
Saxony, do hereby declare the nature of this invention to be as follows:-
Hitherto it has been customary, to prepare finely divided graphite or black lead
for various industrial purposes, by reducing it mechanically and treating it by
Brodie's process, or a modification of the same, which process chiefly consists in
mixing the purified and pulverised graphite with potassium chlorate, then adding
concentrated sulphuric acid, heating the whole over the water bath, washing the
product, and finally drying and calcining it.
The present invention has for its object, to produce the same result as Brodie's
process, but in a much shorter time. For this purpose I employ one of the following
processes;
1. Pulverised graphite is moistened with concentrated nitric or sulphuric acid, or
with a mixture of the said liquids in any proportions, or with a solution of oxygenous
salts (salts containing oxygen) in nitric or sulphuric acid or other acids or in
mixtures of acids, then allowed to stand for a short time, and immediately after-
wards calcined, which produces a strong and peculiar inflation of the mass.
2. Graphite is heated for some time with a solution of a bichromate, or of a
permanganate in an acid or a mixture of acids, subsequently scooped out and
calcined; the potassium chlorate usually employed being thus replaced by a
bichromate or a permanganate, which has never before been used for such a
purpose.
3. Graphite is mixed with potassium chlorate, nitric acid is added, the whole is
heated for some time, subsequently washed and calcined. In some cases, it is not
necessary to wash the material before calcining.
4. Graphite is heated for some time with concentrated nitric acid or concentrated
sulphuric acid, then scooped out, washed (if required) and subsequently calcined.
After having been calcined and thereby inflated, the graphite is thrown into water
and stirred, during which operation the impurities are either dissolved, or collected
at the bottom, while the inflated graphite is light enough to float on the water.
Subsequently the graphite is scooped off and is now ready to be used for certain
purposes. For other purposes should be more finely divided, which may be
effected by using the graphite which has been treated by one of the above methods
and thereby inflated, as a raw material for one of the four processes described
above, that is to say, by treating the same material repeatedly.
Dated this 11th day of June 1891
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Treatment or Purification of Graphite to Render
it Suitable for Industrial Purposes.
I, WILLIAM LUZI, Chemist, of 18, Hospitalstrasse, Leipzig, in the Kingdom of
Saxony, do hereby declare the nature of this invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:―
Hitherto it has been customary, to prepare finely divided graphite or black lead

page_text: for various industrial purposes, by reducing it mechanically and treating it by
Brodie's process, which chiefly consists in mixing the purified and pulverized
graphite with potassium chlorate, then adding concentrated sulphuric acid, heating
the whole over the water bath, washing the product, and finally drying and
calcining it.
A modification of this process consists in heating the graphite with a mixture of
1 part of concentrated nitric acid and 4 parts of concentrated sulphuric acid,
washing the product with water, subsequently drying and calcining the same.
In both cases the graphite expands peculiarly during calcination and assumes a
state of fine distribution.
Instead of these known methods, I employ others, hereinafter described under 1
to 4, which differ essentially from the above by avoiding the separate operations of
boiling, washing and drying, and substituting therefor a simple calcination with
the necessary reagents. They also show, that it is unnecessary, to separate the
graphite from the respective reagent before calcination, which has hitherto been
done in Brodie's process..
First method: Pulverized graphite (either coarse or fine) is moistened with
concentrated nitric or sulphuric acid, or with a mixture of the said liquids in any
proportions, or with a solution of oxygenous salts, (salts containing oxygen) in
nitric or sulphuric acid or other acids or in mixtures of acids, then allowed to stand
for a short time, and immediately afterwards calcined, which produces a strong and
peculiar inflation of the mass.
The vermiform product thus obtained is very plastic and can be easily pressed
into various moulds. The process just described, may, however, be modified
as follows;
The graphite is thoroughly moistened with nitric acid or with a mixture of
nitric and sulphuric acid,, by immersing it in the same for a short time, or allowing
it to stand under the liquid; subsequently the graphite is washed until the water
flowing off is free from acid, and then calcined, which treatment serves at the same
time to recover almost the whole of the acid.
Second method: Graphite is heated for some time with a solution of a bi-
chromate, or of a permanganate, in an acid or a mixture of acids, subsequently
scooped out and calcined; the potassium chlorate usually employed being thus
replaced by a bichromate or a permanganate which has never before been used for
such a purpose.
Third method Graphite is mixed with potassium chlorate, nitric acid is added,
the whole is heated for some time, subsequently washed and calcined. In some
cases, it is not necessary to wash the material before calcining.
Fourth method: Graphite is heated for some time with concentrated nitric acid
or concentrated sulphuric acid, then scooped out, washed (if required) and
subsequently calcined.
After having been calcined and thereby highly inflated, the graphite is thrown
into water and stirred, during which operation the impurities are either dissolved,
or collected at the bottom, while the inflated graphite is light enough to float on
the water. Subsequently the graphite is scooped off and dried and is now ready
to be used for certain purposes, for instance, for being pressed into sheets. For
other purposes it should be more finely divided, which may be effected by using
the graphite, that has been treated by one of the above methods and thereby inflated,
as a raw material for one of the four processes described above, that is to say, by
treating the same material repeatedly.
The processes described under (1) which only consist in thoroughly moistening
the graphite with certain reagents, and directly calcining it, have all been dis-
covered by myself and possess the advantage of attaining the desired result in a
much shorter time, than Brodie's methods.
The possibility of using permanganates in method No. 1, and of merely using
concentrated nitric acid in inethod No. 4 has also been discovered by myself, and
none of the processes described have ever been used in practice.

page_text: The principal feature of method No. 2 consists in replacing potassium chlorate
by bichromates or permanganates; process No. 3 substitutes for the sulphuric
acid of Brodie's mixture (consisting of potassium chlorate and sulphuric acid)
nitric acid, of which only small quantities need be employed. Method No. 4
shows, that it is sufficient, to use only concentrated sulphuric acid or only
concentrated nitric acid, without the addition of any oxidising salts.
The graphite purified and prepared by the processes described may be moulded,
to form vessels, plates, cylinders, tubes, or rods by means of pressure; or it may
be used for the construction of rheostats or other electrical apparatus; or for the
manufacture of pencils; for smoothing or polishing gun-powder or other explosive
powder, to protect it against moisture for the manufacture of alloys; also as a
substitute for vegetable or animal charcoal in clarifying, purifying or disinfecting
liquids; for the manufacture of lubricants or pigments, crucibles, fireproof utensils,
binding substances, polishing powders; for sharpening knives; for the production
of carbon-compounds, such as graphitic acid, mellitic acid; for the construction
of "platinised graphite" and other batteries, for which purpose the mass is
specially suitable, on account of its plasticity, which renders the use of a binding
substance unnecessary, whereas the ordinary graphite always retains the nature of
a powder and cannot be moulded to form variously shaped solid objects, without
the addition of a binding substance.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be prepared, I declare that what I
claim is:-
1. The preparation or purification of graphite by moistening the same with
concentrated nitric acid, with concentrated sulphuric acid, or with a mixture of
the two, or with a solution of oxygenous salts in acid, and immediately or a short
time afterwards calcining it; or by thoroughly moistening the graphite with
concentrated nitric acid, or with a mixture of concentrated nitric acid and con--
centrated sulphuric acid as described, subsequently washing it (until the water
flowing off is free from acid) and calcining; or by heating the graphite with a
solution of a bichromate or permanganate in acid, or in a mixture of acids,
subsequently scooping out and calcining it: or by using Brodie's process with the
modification, that the sulphuric acid is replaced by nitric acid; or by heating
graphite only with concentrated nitric acid or concentrated sulphuric acid,
scooping it off, eventually washing and calcining the same, all substantially as
described.
Dated this 7th day of March 1892