Year: 1888

page_text: Date of Application, 10th Jan., 1888
Complete Specification Left, 27th Aug:, 1888
Complete Specification Accepted, 28th Sept., 1888
I, JAMES PARK, of Millburn Chemical Works, Glasgow, in the County of Lanark
North Britain, Chemist, do hereby declare the nature of this Invention to be as follows,
that is to say -
My said Invention has for its object the obtainment of chromium in the metallic
condition in an improved manner.
In carrying out my Invention I first form an intimate mixture of pulverised oxide
of chromium and carbon, by heating a mixture of bichromate of ammonium and
sugar. Or starch or other similar carbonaceous substance may be substituted for the
sugar. I find suitable proportions to be five parts by weight of bichromate of
ammonium to four parts of sugar. I heat the mixture in an iron pan or vessel of a
capacity at least twice as great as what would be filled by the mixture, and I apply
to the vessel a cover of wire gauze or perforated iron which will prevent loss of oxide
of chromium and carbon whilst allowing of the escape of the gases or vapors evolved
during the decomposition. The bichromate of ammonium may be heated by itself to
obtain the oxide of ichromium, to which carbon may subsequently be added in any
convenient way.
For the second stage the oxide of chromium and carbon after being finely ground
together, if required, are tightly packed into a graphite or plumbago crucible, and
the lid luted on with a little argol or fine carbon to prevent entrance of air. The
crucible with its contents is subjected to a white heat for at least an hour; and when
removed from the furnace is allowed to cool in an atmosphere consisting of a non-
oxidising gas or gaseous mixture such as coal gas. When removed from the crucible
the contents will be found to consist of particles of metallic chromium cohering
more or less and which may be described as spongy chromium.
For the third and final stage the spongy chromium is pulverised; and if it contains
any sensible amount of carbon a little oxide of chromium is mixed with it. It is then
tightly packed in a graphite or plumbago crucible, and is subjected to a very high

page_text: temperature obtained by means of a coke fire aided by a blast of heated air. In this
way a solid mass of pure or nearly pure chromium is obtained which exhibits a tin-
white fracture.
Either the spongy or the solid chromium may be used for forming alloys with iron
or other metals.
EDMUND HUNT,
Applicant's Agent.
I, JAMES PARK, of Millburn Chemical Works, Glasgow, in the County of Lanark
North Britain, Chemist, 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, that is to say:
My said Invention has for its object the obtainment of chromium in the metallic
condition in an improved manner.
The processes employed in completely carrying out my Invention comprise three
stages.
In the first stage I form an intimate mixture of oxide of chromium and carbon in a
state of fine division by heating a mixture of bichromate of ammonium and sugar.
Or starch or other similar carbonaceous substance may be substituted for the sugar.
I find suitable proportions to be five parts by weight of bichromate of ammonium to
four parts of sugar; or the quantity of sugar may be increased to four and a half or
five parts without detriment. The materials are ground together and the mixture is
heated in an iron pan or vessel of a capacity at least twice as great as what would
be filled by the mixture. The vessel is provided with a cover of wire gauze or
perforated iron which will prevent loss of oxide of chromium and carbon whilst
allowing of the escape of the gases or vapors evolved during the reaction. Heat is,
applied, at first gently, and is continued as long as nitrogen, carbonic acid, and water
are given off. leaving an intimate mixture of oxide of chromium and carbon.
Or the bichromate of ammonium may be dissolved in a small quantity of water at
the boiling temperature, and the sugar may be added to the solution, being at first
added in successive small quantities. The heat is continued until the mass is quite
dry, a most intimate mixture of oxide of chromium and carbon being thereby
formed.

page_text: In
Or the bichromate of ammonium may be first converted to oxide of chromium by
heing heated in a vessel such as is hereinbefore described, and then charcoal or other
suitable form of carbon may be ground and mixed with the oxide of chromium.
this modification of the first stage of the processes about three parts by weight of
charcoal may be ground with the oxide of chromium obtained from twenty parts of
bichromate of ammonium. A mill having edge runners or any other suitable grinding
mill may be used; but the materials must be reduced to a state of very fine division
and be thoroughly incorporated.
In the second stage the mixture of oxide of chromium and carbon obtained in the
first stage, is packed tightly into a graphite or plumbage crucible, provided with a lid
of the same material which is carefully luted with argol or with fine carbon made into
a paste with water or other suitable medium. The crucible with its contents is, in a
suitable furnace, subjected to a white heat for at least an hour, or for a period deter-
mined by the size of the crucible and the quantity of materials operated on, and
sufficient to reduce the oxide of chromium to the metallic state. The crucible is after-
wards allowed to cool in an atmosphere of coal gas or other suitable non-oxidising gas.
When removed from the crucible the contents will be found to consist of particles of
metallic chromium cohering more or less, and which may be described as spongy
chromium.
In the third stage the spongy chromium is finely pulverised and placed in another
and smaller crucible and is covered with a layer of fine charcoal or with argol to
prevent oxidation, and is again heated in a furnace. This time the heat should be as
high as can be obtained with a gas or coke fire urged with a blast of heated air. The
spongy chromium is thereby converted into a inass of pure or nearly pure chromium.
Other compounds of chromic acid and ammonia besides the bichromate may be used
in carrying out my Invention but not so advantageously.
Either the spongy or the solid chromium may be used for forming alloys with
iron or other metals. If a rich alloy of chromium and iron is wanted, one or
more parts of oxide of iron in a state of fine division may be added to the mixture
of bichromate of ammonium and sugar in the first stage of the processes, to be reduced
to the metallic state along with the chromium in the second stage. Or metallic iron
may he added in the desired proportion to the spongy chromium and be heated
together with it in the third stage.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :--
1 The obtaining of chromium by first heating bichromate or other chromate of
ammonium and sugar or other suitable carbonaceous matter to obtain a mixture of
oxide of chromium and carbon, secondly heating the oxide of chromium and carbon
to form spongy chromium and thirdly heating the spongy chromium to form compact
or solid chromium substantially as hereinbefore described.
2-The obtaining of chromium by mixing oxide of chromium obtained by heating
bichromate or other chromate of ammonium with carbon and heating the mixture to
form spongy chromium; and by subsequently heating the spongy chromium to form
compact or solid chromium substantially as hereinbefore described.
3-The obtaining of oxide of chromium by heating bichromate or other chromate
of ammonium substantially as and for the purposes hereinbefore described.
Dated this Twenty-fourth day of August 1888.
EDMUND HUNT,
Applicant's Agent.