An Improved Process for the Preparation and Purification of Solutions of Copper.
Year: 1896

page_text: An Improved Process for the Preparation and Purification of
Solutions of Copper.
I, JOHN CAMERON GRAHAM, of 2 Garden Court, Temple, in the City of London,
Barrister-at-Law, do hereby declare the nature of this invention to be as follows:-
In the deposition of copper electrically from solutions I have found it impossible
to obtain a deposit of a good colour either from a solution of chloride of copper or
from a solution of a copper salt which contains even a very small proportion of
bydrochloric acid.
My present invention relates to an economical method of converting a chloride
of copper into such a salt as a sulphate and to a method of purifying and concen-
trating solutions of copper more particularly applicable to solutions which contain
other metals in solution besides copper.
I will describe both heads of this invention with reference to solutions which
contain considerable quantities of copper, iron, soda etc. in solution as chlorides
such as are prepared in considerable quantities by lixiviating ores.
When an alkali or lime is added to such a solution the iron is displaced before
the copper, and is thrown down as a hydrated oxide of iron, the copper salt remain-
ing in solution. I accordingly add as much alkali or lime as will displace the
iron, the amount required is readily ascertained by experiment and depends upon
the amount of iron etc. present. Care must be taken to stop adding the base
before any appreciable quantity of copper is thrown down.
The precipitate which is very bulky is allowed to settle and the clear fluid which
contains the soluble copper salt is drawn off.
To this fluid a further quantity of the base is added, sufficient to throw down
the whole of the copper as a hydrated oxide, which is allowed to settle and the
fluid above is then drawn off.
This hydrated oxide of copper must be very thoroughly washed because it holds
a quantity of chlorine which cannot easily be got rid of by mere washing and
settling. I have found the best way of doing this is to churn the precipitate
together with the water through a centrifugal pump for a few minutes by which
means the precipitate is thoroughly broken up and washed. This occasions a
considerable amount of frothing during the first washing.
The precipitate is then allowed to settle, the fluid drained off, fresh water added
and the churning repeated and the precipitate again allowed to settle.
To this precipitate now free from chlorine is added any suitable acid, sulphuric
acid being the best, and thus a tolerably pure and concentrated solution of sulphate
of copper may be obtained from a dilute and impure solution of chloride of copper.
the original impure solution was a sulphate and not a chloride then the second
addition of the base may be dispensed with.
If now a lead or other insoluble anode be used in the èlectrical deposition of the

page_text: copper so prepared the sulphuric acid will be set free and may be again used for
dissolving a further quantity of the copper precipitate.
Dated this 1st day of August 1896.
MARKS & CLERK,
18 Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.
An Improved Process for the Preparation and Purification of
Solutions of Copper.
I, JOHN CAMERON GRAHAM, of 2 Garden Court, Temple, in the City of London,
Barrister at Law, 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:-
In the deposition of copper electrically from solutions I have found it impossible
to obtain a deposit of a good colour either from a solution of chloride of copper or
from a solution of a copper salt which contains even a very small proportion of
hydrochloric acid.
My present invention relates to an economical method of converting a chloride
of copper into such a salt as a sulphate and to a method of purifying and concen-
trating solutions of copper more particularly applicable to solutions which contain
other metals in solution besides copper.
I will describe both heads of this invention with reference to solutions which
contain considerable quantities of copper, iron, soda etc. in solution as chlorides
such as are prepared in considerable quantities by lixiviating ores.
When an alkali or lime is added to such a solution the iron is displaced before
the copper, and is thrown down as a hydrated oxide of iron, the copper salt remain-
ing in solution. I accordingly add as much alkali or lime as will displace the
iron and such of the other metals as are displaced before the copper; the amount
required is readily ascertained by experiment and depends upon the amount
of iron etc. present. Care must be taken to stop adding the base before any
appreciable quantity of copper is thrown down.
The precipitate which is very bulky is allowed to settle and the clear fluid which
contains the soluble copper salt is drawn off.
To thi, fluid a further quantity of the base is added, sufficient to throw down
the whole of the copper as a hydrated oxide, which is allowed to settle and the
fluid above is then drawn off.
It is essential that this hydrated oxide of copper should be very thoroughly
washed Lecause it holds a small quantity of chlorine or chlorides which cannot
easily e got rid of by mere washing and settling and which must be removed
if the copper when redissolved is to be used for electrodeposition. I have found
the best way of doing this is to churn the precipitate together. with the water
through a centrifugal pump for a few minutes by which means the precipitate is
thoroughly broken up and washed. This occasions a considerable amount of
frothing during the first washing.
The precipitate is then allowed to settle, the fluid drained off, fresh water added
and the churning repeated and the precipitate again allowed to settle.
To this precipitate now free from chlorine is added any suitable acid, sulphuric
acid being the best, and thus a tolerably pure and concentrated solution of sulphate
ct copper may be obtained from a dilute and impure solution of chloride of copper.

page_text: If the original impure solution was a sulphate and not a chloride then the second
addition of the base may be dispensed with.
If now a lead or other insoluble anode be used in the electrical deposition of the
copper so prepared the sulphuric acid will be set free and may be again used for
dissolving a further quantity of the copper precipitate.
I am aware that it has been proposed to prepare protoxide of copper, from solutions
containing cupreous chloride and iron salts, by throwing down first the iron, and
then the copper by means of alkalies and similar bodies.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
The above described method of throwing down the copper and washing it
thoroughly so as to make it when redissolved suitable for electrodeposition.
Dated this 23rd day of April 1897
MARKS & CLERK,
18 Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.