IMPROVEMENTS IN SMELTING COPPER
Year: 1848

page_text: MITCHELL, ALDERSON, AND WARRINER'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JOHN
MITCHELL, Chemist, HENRY ALDERSON, Civil Engineer, and THOMAS WARRINER,
Farmer, of Lyons Wharf, Upper Fore Street, Lambeth, in the County of
Surrey, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-eighth day of December, in the twelfth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto us, the
said John Mitchell, Henry Alderson, and Thomas Warriner, Her especial
license, full power, sole privilege and authority, that we, the said John Mitchell,
Henry Alderson, and Thomas Warriner, our exors, adñiors, and assigns, and
such others as we, the said John Mitchell, Henry Alderson, and Thomas
Warriner, our exors, admors, or assigns, should at any time agree with, and no
others, from time to time and at all times during the term of years therein
mentioned, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, and in all Her
Majesty's Colonies and Plantations abroad, and in the Islands of Jersey,
Guernsey, Alderney, Sark, and Man, our Invention of "IMPROVEMENTS IN
SMELTING COPPER;" in which said Letters Patent is contained a proviso, obliging
us, the said John Mitchell, Henry Alderson, and Thomas Warriner, by an
instrument in writing under our hands and seals, or under the hand and seal
of one of us, particularly to describe and ascertain the nature of our said Inven-
tion, and in what manner the same is to be performed, and to cause the same

page_text: to be inrolled in Her Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said in part recited Letters
Patent, as in and by the same, reference being thereunto had, will more fully
and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said John
Mitchell, on behalf of myself and of the said Henry Alderson and Thomas
Warriner, do hereby declare that the nature of our said Invention, and the
manner in which the same is to be performed, is particularly described and
ascertained in and by the following description thereof, that is to say:-
This Invention consists of improvements in obtaining metallic copper from
certain copper ores and other substances containing copper. The substances
which are intended to be treated by the methods to be described are, first, the
any other
sulphurets of copper; second, the sulphurets of copper mixed with
metallic sulphuret or sulphurets; third, a sulphuret of copper containing a
sulphate or other salt of copper; fourth, sulphuret of copper mixed with any
other metallic sulphuret or sulphurets containing sulphate or other salt of
copper fifth, carbonates or oxides of copper; sixth, a mixture of carbonato
aud oxide of copper containing a sulphuret of copper or a sulphuret of other
metal; seventh, a carbonate or oxide of copper, or a mixture of a carbonate
and oxide of copper with a sulphuret of copper mixed with other metallic
sulphurets; eighth, a mixture of any of the above carbonates or oxides or
éarbonates and oxides with a metallic sulphuret or sulphurets and a sulphate
or other salt of copper; ninth, carbonate or oxide of copper, or a carbonate
and oxide of copper mixed with a sulphate or other salt of copper.
In the ordinary method of copper smelting the sulphuret ores are subjected
to a numerous series of alternate roastings and fusions, the ultimate object of
which is to convert all the sulpher they may contain into sulphurous acid, and
the iron and the copper into oxides. The oxide of iron passes off in the
siliceous slag, whilst the copper is concentrated in the regulus, which at last is
brought into such a state by the above operations that it contains but little
sulphur and iron, both of which substances are removed by the refining process
which in this stage it has to undergo, and the copper thus produced is either
east into ingots, or is submitted to another operation, by which it acquires the
desired degree of malleability.
It is therefore evident that the object of all the above operations is to remove
the sulphur and iron. This is done progressively and at the same time in the
process just described. Now, we propose to divide this into two distinct
operations: first, the sulphur will be entirely removed by treating a rich ore
or a regulus (obtained without the addition of iron or alkali) in a finely-divided

page_text: state, in the manner to be hereaftor described; secondly, the iron will be sepa-
rated, and the copper obtained in a comparatively pure state, by. treating the
mixed oxides resulting from the first operation with siliceous and carbonaceous
matters without the use of iron or the application of electric currents.
Thus, by the new process, the smelting, or production of copper from copper
ores, is effected by fewer operations and in a much shorter time than in the
ordinary process. In many cases but one roasting and one fusion will be
necessary, and in others, at most, two roastings and two fusions.
The chief difficulty in getting rid of the last traces of sulphur depends upon
the circumstance that during the ordinary roasting of sulpher ores of copper
the whole of the sulphur is not expelled in the gaseous state as sulphurous acid,
but a portion is converted into sulphuric acid, which unites with a corresponding
equivalent proportion of oxides of copper and iron to form sulphates of copper
and iron. This, however, is not all, for if lime, baryta, strontia, or magnesia
be present, either in the caustic or carbonated state, then a still greater
quantity of sulphuric acid is retained by those bases to form sulphate of lime,
baryta, strontia, or magnesia.
Now we have found that whilst sulphates either of copper, iron, lime,
baryta, strontia, (these three latter sulphates may be disregarded in practice,
as the results they produce are not sufficiently marked to be injurious,) and
magnesia are present, that on reducing the mixture of oxides of copper and
iron, and the sulphates of iron, copper, &c., the latter are decomposed, giving
rise to the production of sulphurets of iron and copper in addition to the
metallic copper and iron produced, so that a very considerable portion has to
undergo a further roasting. In the new process about to be described this
difficulty is overcome.
Again, when a mixture of oxides of copper and iron free from sulphur are
to be reduced, it will be found that copper is indeed separated, but containing
a very large quantity of iron. The copper so produced would, therefore, have
to be refined in order to fit it for the market. This we also avoid by forming
silicates of copper and iron, and then reducing by carbonaceous matter; the
silicate of copper is completely reduced and separated, whilst the silicate of iron
is left intact.
Owing to the influence of the presence of lime, baryta, strontia, and magnesia
(more especially the latter earth) on the roasting process, we divide all copper
ores, and other substances enumerated as susceptible of treatment by the
present process, into two.grand classes, thus:-
First class, those ores or substances containing neither lime, baryta, strontia,
or magnesia in the caustic or carbonated state, or in the state of sulphate.

page_text: Second class, those ores or substances which contain lime, baryta, strontia,
or magnesia (more especially the latter) in the caustic or carbonated state, or
in the state of sulphate.
We subdivide each of the preceding classes into two orders, videlicet:-
Order 1, those oras or substances which contain more than twenty-five per
cent. of copper.
Order 2, those ores or substances which contain less than twenty-five per
cent. of copper.
.
All ores, and other substances enumerated as susceptible of treatment by the
present process, and which belong to Class 1, may be treated according to
process No. 1, whether they belong either to Order 1 or 2.
Process No. 1.-Treatment of Copper Ores of the First Class.
The finely pulverized (fine dressed) ore is placed in a reverberatory furnace,
known as a "calciner," (a furnace constructed according to Sheffield's Patent,
having air passing through openings in the bridge over the roasting ore in the
furnace is preferred,) and exposed to a gradually increasing temperature until
it arrives at a full red heat. During the whole of the time it is in the furnace
it is stirred from side to side and from end to end, in order to expose the
greatest possible surface to the oxidating action of the heated atmospheric air
passing over the roasting matter; this is to be continued until the ore ceases
to smell of sulphurous acid. The heat is now to be increased as much as
possible, taking care, however, that the heated ore does not in the slightest
degree agglutinate, (this point must be particularly attended to,) the stirring
all this time being constant. The object of the increased heat is the decom-
position of the sulphate of copper formed during the earlier stage of the
roasting. At the higher temperature this salt is decomposed and its acid
expelled. This may be facilitated by the addition of small quantities of any
carbonaceous matter, as is already known.
After it has been in this state about half an hour, a sample is to be taken
out, mixed with a small quantity of water and well stirred, allowed to settle,
and the clear supernatant liquid poured off. If on the addition of solution of
ammonia the liquid assumes a blue tint, or on the addition of ferrocyanide of
potassium a reddish tint, the heat is to be continued for another half hour,
after which time it is again to be tested in the same manner, and so on, until
no copper can be detected in the aqueous solution. The ore may now be
drawn from the furnace, and is ready for the reducing operation, to be hereafter
described.

page_text: Process No. 2.-For Ores and Substances of the Second Class, enumerated as
susceptible of Treatment by this Process.
The finely pulverized (fine dressed) ore is to be roasted precisely as de-
scribed for ores of Class No. 1, but before being ready for the reducing process
it has to undergo the following operation, which has for its end the separation
of the sulphate of magnesia which has withstood decomposition. (As before
stated, the danger attached to the presence of the sulphate of lime, baryta, and
strontia is so small that in practice it may safely be disregarded.) The roasted
ore while still hot is conveyed into a tank (provided with a false bottom)
containing a considerable quantity of water, and well agitated; after having
remained in the water about three or four hours with occasional agitation,
the water containing sulphato of magnesia in solution is run off from the
bottom of the tank, and the ore thus washed allowed to drain as much as
possible. It is then removed and dried, and is fit for the reducing process.
In case, however, the ore contains less than twenty-five per cent. of copper
(Order 2nd), it is thrown into a fusion or "metal" furnace with a certain
quantity of lime or old slag, as is usual in such operations, and the regulus so
produced is run into sand moulds or into water. We prefer to give the ore a
partial roasting before forming a regulus, as in the following process:-The
finely pulverized (fine dressed) ore is placed in the furnace, " calciner," already
described, and exposed to a dull red heat until very little or no more sul-
phurous acid can be smelt. The ore is then removed to another reverberatory
furnace, known as a "fusion" or "metal" furnace, and mixed with an
appropriate quantity of lime, or lime and old shag, to form a fluid mixture
when exposed to a sufficient temperature. When the whole is well fused, the
furnace is tapped and the regulus run into either sand moulds or water. The
regulus produced by either of the preceding methods is reduced to a state of
fine division, and in that state it is roasted, exactly as described for ores and
substances Class 1, Process 1, after which it is ready for reducing.
Reducing Process.
The roasted ore or regulus is mixed with such a proportion of sand as
will correspond to the amount of oxide of copper and oxide of iron in the
substance. Thus, if the mixed oxidos consist of about eighty-eight per
cent. of oxide of copper and the remainder be oxide of iron, from thirty-five
to forty per cent. of sand are required, with such a quantity of lime or

page_text: the proportion of about one-tenth of the weight of the sand and lime or sand
and slag. When the whole is well fused, a further portion of coal or other
carbonaceous matter is to be added to the fused mass and well stirred together;
the heat is then to be increased for a short time and the whole well stirred
again; a portion of the slag is to be taken out and tested for copper by any
ordinary method. If but traces be present, the operation is finished, and the
furnace may be tapped; but if copper be present in quantity, more coal or
carbonaceous matter must be added, and the mass must be again stirred, and
so on, until the slag is nearly free from copper, as above.
Having now described our improvements, and the best means with which
we are acquainted for carrying the same into effect, we would observe, in con-
clusion, that under the herein-before in part recited Letters Patent we claim
the obtaining of metallic copper from the orcs of that metal by the processes
herein-before described, (videlicit,) by effectually separating the sulphur from
the metals by roasting the ore in the maner described under process No. 1,
and by roasting and washing as described under process No. 2, and (when the
ore is poor) by forming a regulus without the use of iron and alkali, and sub-
sequently roasting, as is also described under process No. 2; by separating the
iron from the mixed oxides resulting from the roasting processes by the
employment of siliceous and carbonaceous matters, as above described, for the
purpose of obtaining the copper contained in such oxides in a pure state.
In witness whereof, I, the said John Mitchell, have hereunto set my
hand and seal, this Twenty-eighth day of June, in the year of our Lord
One thousand eight hundred and forty-nine.
JOHN (L.S.) MITCHELL.
Enrolled the Twenty-eighth day of June, in the year of our Lord One
thousand eight hundred and forty-nine.