IMPROVEMENTS IN TREATING CERTAIN ORES AND ALLOYS, AND IN OBTAINING PRODUCTS THEREFROM
Year: 1859

page_text: LETTERS PATENT to William Henderson, of Alderley Edge, in the County
of Chester, Chemist, for the Invention of "IMPROVEMENTS IN TREATING
CERTAIN ORES AND ALLOYS, AND IN OBTAINING PRODUCTS THEREFROM."
Sealed the 22nd May 1860, and dated the 20th December 1859.
PROVISIONAL SPECIFICATION left by the said William Henderson at the
Office of the Commissioners of Patents, with his Petition, on the 20th
December 1859.
I, WILLIAM HENDERSON, of Alderley Edge, in the County of Chester,
Chemist, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN TREATING CERTAIN ORES AND ALLOYS, AND IN OBTAINING PRODUCTS
THEREPROM," to be as follows:-
These improvements relate, first, to the treatment of copper and several
other ores when they exist as or have been reduced or converted to the state
of oxides, carbonates, or other salts of copper, or other metal, and especially
when associated with silica or other matter insoluble in dilute acids.
Secondly, to the treatment of ores of copper, lead, zinc, antimony, silver,
cobalt, and several other metals when they occur as sulphurets, mixed or
singly, and combined with sulphur and iron, as iron pyrites, containing all or
either of these metals, or partially calcined or burnt, and being then a mixture
of oxides, sulphates, and sulphurets, with or without silica.
And, thirdly, to similar compounds when they exist wholly as oxides or
salts, and associated with much silicious matter.
The first class of ores I treat in the following manner :-When any sub-
oxide of copper exists in the ore, it should be reduced to coarse powder and
heated red hot and calcined in an open furnace, with free admission of air

page_text: until the suboxide is converted into the protoxide of copper.
If the ore
consists only of carbonates and protoxides, this calcination is unnecessary.
The ore roughly crushed and as dry as possible is introduced into vats with
false bottoms, constructed and worked as particularly described in the Speci-
fication of a Patent granted to me, No. 2517, and dated 30th Septr. 1857.
The ore is then covered with dilute sulphuric acid, of from 1.20° to 1-40°
specific gravity, according to the richness and condition of the ores. When
this acid has been repeatedly pumped over and allowed to percolate downward
through the ore and under the false bottom, and has become completely
saturated with copper or other metal, it is tapped into another vessel or
receiver; the ore, if necessary, is treated with fresh acid until exhausted. The
residue is well washed with hot water, and the exhausted residue wheeled to
the waste heap. The solutions are concentrated in leaden pans as far as
possible without salting, the strong liquor may then be run direct into a
furnace and evaporated to dryness at a gentle heat. The resulting dry
sulphate of copper contains only one equivalent of water. The concentrated
solutions may also be crystallized, and the crystals. dried at 320° Fahr. The
dry sulphate of copper is then introduced into a retort or close calcining
furnace and heated to bright redness. The protoxide of copper at a red heat
parts with the whole of its sulphuric acid, which passes off as a heavy vapour,
and is conveyed from the furnace by flues into a leaden chamber or condenser.
Sometimes, through the presence of organic matter or protosulphate of iron
in the solutions or crystals, some of the sulphuric acid is reduced to sulphurous
acid, and will require a proportionate quantity of nitric acid gas to convert it
into sulphuric acid again, as is well understood in sulphuric acid works.
When the sulphate of copper in the retort or furnace ceases to emit fumes
when subjected to a bright red heat, the residue is withdrawn from the furnace
or retort, and will be found to be oxide of copper, more or less pure. This
oxide is then mixed with carbonaceous matter, and a small quantity of silicious
ore free from sulphur, and smelted in a reverberatory furnace in the usual
manner. The result will be, rough copper perfectly free from regulus, and fit
for refining. When the copper or other ore contains silver, cobalt, nickel, or
manganese, in such a state as can be dissolved by dilute sulphuric acid by
calcining the dry sulphate of copper at a low red heat, and afterwards washing
with hot water the resulting oxide of copper, the undécomposed sulphates of
these metals will be dissolved out and separated from the copper. The
sulphurets of copper, zinc, and several other metals when thoroughly calcined
may be dissolved in dilute sulphuric acid, the sulphates dried and heated to
redness, and the resulting oxides reduced in the usual manner.

page_text: The second class of ores I treat as follows:-If the proportion of sulphur
existing in the ore is more than 1 times that of the metal or metals to be
extracted, it should be reduced by calcination to that point, or if the ore
contains much silica the proportion of sulphur may be even lower than equal
proportions. The ores are then reduced to fine powder, the finer the better,
and mixed with from 5 to 50 per cent. of common salt. The mixture is
then placed in retorts or close calcining furnaces, having flues or pipes com.
municating with the interior of the furnace or retort and a condensing
apparatus. In these furnaces the mixture is subjected to various degrees of
heat according to the nature of the ore and the metal contained in it. If the
ore contains much sulphur and little silica, the heat must be applied carefully at
first, and gradually increased, stirring at short intervals. When the ore is one
of copper or zinc, and has been previously calcined, the mixture of salt and
pulverized ore may be at once subjected to a bright red heat, the volatilized
chlorides are condensed with water, the ore is withdrawn from the furnace
whenever it ceases to smoke strongly, and if any copper or other metal stil!
remains in the calcined ore, it is only necessary to wash it with the hot and
acid solution of copper or other metal from the condenser, and the last trace
of copper or other metal may be thus extracted. The copper or metal is
extracted from these solutions by precipitation, and the sulphate of soda may
be afterwards obtained by evaporation and crystallization. When a mixed ore
is under treatment containing metals whose chlorides volatilize at different
temperatures wide apart, such as copper and tin, copper or zinc and arsenic.
lead and antimony, I employ a furnace with two or more beds one above the
other, and all heated by the same fire or fires, each bed having a separate
condenser. By this means the arsenic, tin, or antimony, would be volatilized
in the upper and colder beds and separately condensed, and the copper, lead,
or zinc in the lower and hotter beds.
The third class of ores I treat exactly as the second class, the silica taking
the place of the sulphur, and decomposing the salt at a red heat. The heat
when the proportion of salt used is under 30%, may be at once urged to
bright redness, and sustained at a full bright red heat.
When an ore is
deficient in sulphur, and contains little silica, such as the calcined or burnt
pyrites or mundics containing copper and other metals, and from which nearly
all the sulphur has been extracted for the manufacture of sulphuric acid, I add
about 10 per cent. of sand or other silicious matter. Several alloys may be
separated by this process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Henderson in the Great Seal Patent Office on the
20th June 1860.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HENDERSON, of Alderley Edge, in the County of Chester, Chemist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing dato the Twentieth day of December, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-third year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said William Henderson, Her special licence that I, the said
William Henderson, my executors, administrators, and assigns, or such others
as I, the said William Henderson, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at
all times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN TREATING CERTAIN ORES AND ALLOYS, AND IN OBTAINING
PRODUCTS THEREFROM," upon the condition (amongst others) that I, the said
William Henderson, my executors or adininistrators, by an instrument in
writing under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
.
NOW KNOW YE, that I, the said William Henderson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:
These improvements relate, first, to the treatment of copper and several
other ores when they exist as or have been reduced or converted to the state
of oxides, carbonates, or other salts of copper or other metal, and especially
when associated with silica or other matter insoluble in dilute acids.
Secondly, to the treatment of ores of copper, lead, zinc, antimony, silver,
cobalt, and several other metals when they occur as sulphurets mixed, or
singly, or combined with sulphur and iron as iron pyrites, containing all or
either of these metals, or partially calcined or burnt, and being then a mixture
of oxides, sulphates, and sulphurets with or without silica.

page_text: And, thirdly, to similar compounds when they exist wholly as oxides or salts,
and associated with much silica.
The first class of ores I treat in the following manner :-When a large pro-
portion of the red or suboxide of copper exists in the ore, it should be reduced
to coarse powder, and heated red hot, and calcined in an open furnace, with
free admission of air, until all the red or suboxide is converted into the black
or protoxide of copper. When the ore contains only a small proportion of
suboxide of copper, or when, through local or other causes, the preliminary
calcination is inconvenient or objectionable, I use sulphuric acid containing
nitrous or nitric acid, which readily dissolves the suboxide of copper. Or the
ore may be treated in the usual way with sulphuric acid, and the remaining
suboxide may be extracted or separated by dressing or washing with water,
as is well understood. If the ore contains no suboxide or sulphuret of copper,
neither the preliminary calcination nor the use of nitric acid is necessary.
The ore then roughly crushed, and as dry as possible, is introduced into vats
with false bottoms, constructed and worked as particularly described in the
Specification of an Invention for which Her Majesty's Letters Patent,
N° 2517, were granted to me on or about the 30th of September 1857.
The ore is then covered with dilute sulphuric acid of from 1.20 to 1.40
specific gravity, according to the richness and condition of the ores. When
this acid has been allowed to percolate down through the ore, and has been
repeatedly pumped back again until fully saturated with copper or other
metal, it is tapped into another vessel or receiver. The ore, if necessary, is
treated then with fresh acid until exhausted. The residue is well washed with
hot water, and if no cobalt, silver, or other metal worth extracting remains, it
is removed to the waste heap. The solutions of sulphate of copper. or other
metal are concentrated in leaden pans as far as possible without salting.
The strong liquors may then be run into a furnace, and evaporated to dryness
at a gentle heat; the resulting dry sulphate of copper contains only one
equivalent of water. The concentrated solutions may also be crystallized, and
the crystals dried at from 320 to 380° Fahrenheit. The dry sulphate of
copper is then introduced into a retort or close calcining furnace, and heated
to bright redness. The protoxide of copper at a red heat parts with the
whole of its sulphuric acid, which passes off as a heavy vapour, and is con-
veyed from the furnace by flues into a leaden chamber or condenser. Some-
times, through the presence of organic matter or protosulphate of iron in the
solutions or crystals, some of the sulphuric acid is reduced to or leaves the
crystals as sulphurous acid, and will therefore require a proportionate quantity
of nitric acid gas to convert it into sulphuric acid again, as is well understood

page_text: in the manufacture of sulphuric acid by the ordinary way. When the sulphate
of copper in the retort ceases to emit fumes when subjected to a bright red.
heat, the residue is withdrawn from the retort or furnace, and will be found
to be oxide of copper more or less pure. This oxide is then mixed with
carbonaceous matter and a small quantity of siliceous ore free from sulphur,
and smelted in a reverberatory furnace in the usual manner; the result will
be rough copper perfectly free from reulgus, and fit for refining.
To produce metallic copper direct from the anhydrous sulphate, and at the
same time recover all or nearly all the sulphuric acid, I proceed as follows:-
I take the anhydrous or dried sulphate, obtained as has been already described,
or from any other source, and reduce it to powder, and mix it with from 10 to
20 per cent. of charcoal powder, or an equivalent proportion of anthracite coal
or other carbonaceous matter. I prefer charcoal reduced to powder. The
anhydrous sulphate of copper and carbonaceous matter are then intimately
mixed. The mixture is then subjected to a gradually increasing heat in close
vessels, with an escape pipe or flue to convey away the gases to be treated, as
shall be presently described. The close vessels already mentioned may consist
of a series of flues covered with tiles, under which the flames from the fires
pass, and which is well known, and is in common use, as close calcining
furnaces, or they may be clay or cast iron retorts. I much prefer to use a
common cast-iron retort of an oval shape, in no way different from those
extensively used in the manufacture of gas. A bed or stack of these retorts
having been erected and heated up to about 400 degrees Fahrenheit, I then
charge the whole of the retorts quite full with the mixture already described.
As each retort is charged, the door should be screwed up at once.
When all
are filled, the heat is gradually and steadily increased for from 4 to 6 hours,
at the end of which time the heat should not exceed a very dull red beat, and
the charge should be equally well heated all through, and as near as possible
alike in all the retorts. When the discharge of gas has become feeble, the
retorts must be raised to bright redness for half an hour, or until all sulphurous
acid gas has been evolved. I then allow the heat to go back to dull redness
and then unscrew the doors, and the metallic copper in fine particles which,
with the excess of charcoal, is all that remains in the retorts, is then raked out
into iron barrows or waggons; the copper is so far advanced as only to requiro
refining to fit it for the market. The gases evolved from the retorts are a
inixture of carbonic acid and sulphurous acid. All the pipes from the retorts
pass into a main pipe, which is connected with a vitriol chamber, into which
the gases pass, being first mixed with the requisite portion of nitrous gases, as
is well understood in the manufacture of sulphuric acid from the usual sources.

page_text: The chamber is supplied with steam, and worked in every respect as is usually
done in manufacturing sulphuric acid from brimstone. The sulphurous acid
by these means is, with very little loss, readily converted into sulphuric acid,
which I again use for the purpose of extracting the copper from fresh ore.
As soon as the cast-iron retorts are empty, they are charged again. Great
care is required that the heat be not too high at the commencement of the
operation; it should not exceed 400 degrees for the first hour, and be steadily
increased up to 800° or more at the close of the operation. If these pre-
cautions are not carefully observed, sulphuret of copper will be produced. .
When the copper or other ore contains silver, cobalt, nickel, or manganese
in such a state'ns can be dissolved by dilute sulphuric acid, by calcining the
dry sulphate of copper at a bright red heat, and afterwards washing with hot
water the resulting oxide of copper, the undecomposed sulphates of these
metals will be dissolved out and separated from the oxide of copper. When
only cobalt exists in the copper ore treated with dilute sulphuric acid, I con-
centrate the sulphate of copper solutions, as far as possible, without salting,
and then crystallise the sulphate of copper. The mother liquor contains the
sulphate of cobalt. The crystals of sulphate of copper are washed with a small
quantity of cold water, and the washings added to the mother liquor, which is
again evaporated to dryness and heated red hot; the sulphuric acid evolved
being condensed. The dry residue is then reduced to a fine powder and boiled
in water, the undecomposed sulphate of cobalt dissolved out and precipitated
as oxide by an alkali. When peroxide of cobalt is present in the ore, it is not
dissolved by dilute sulphuric acid, I recover it from the insoluble residue by
treating it with concentrated muriatic acid, and I then precipitate the cobalt
from this solution by an alkali or alkaline earth. In treating copper or other
ores with sulphuric acid which contain only a small proportion of silver, on
account of the presence of chlorine in the water and commercial sulphuric
acid, the whole or nearly the whole of the silver is left in the residue. To
extract the chlorido of silver from this residue I wash it with a hot saturated
solution of common salt, the solution is much facilitated by adding to the brine
a small quantity of hyposulphite of soda or lime. The silver is readily obtained
from this solution by precipitation upon copper plates, or I sometimes find it
convenient to precipitate it upon iron or zinc, together with the small propor-
tion of copper remaining in the residue. When an ore contains only oxides
and salts of metals with no sulphurets, and which also contains silver, I sepa-
rate the silver before treating the ore for copper or other metal. When the
crushed ore is put into tanks with false bottoms, I run on the tank of ore a
saturated boiling solution of common salt, which is allowed to percolate down-

page_text: wards through the ore until it comes through hot at the bottom; the brine is
then washed out, and the extraction of copper or or other metal proceeded with,
as has been already described. The silver is very readily obtained from the
solution of common salt by sulphide of sodium, avoiding any excess; the brine
can then be used again. I also employ this process to separato silver from
siliceous and other matter containing no other metal worth extracting. The
sulphurets of copper, zinc, and several other metals, when thoroughly calcined,
I also dissolve in dilute sulphuric acid, dry the crystals, and obtain either the
oxide or metal on the one hand and the sulphuric acid on the other, as has
been already particularly described.
The second class of ores I treat as follows:-If the proportion of sulphur
existing in the ore is more than 1 times as much as the metal or metals to
be extracted, it should be reduced to at least that amount by calcination, or if
the ore contains much silica the proportion of sulphur may be even lower than
equal proportions. The ores are reduced to fine powder, the finer the better, and
mixed with from 5 to 50 per cent. of common salt. The mixture is then placed
in retorts or close calcining furnaces, having flues or pipes communicating with
the interior of the furnace or retort, and a condensing apparatus. In theso
furnaces the mixture is subjected to various degrees of heat, according to the
nature of the ore and the metal or metals contained in it. If the ore contains
much sulphur and little silica, the heat must be applied carefully at first, and
gradually increased, stirring at short intervals. When the ore is one of copper
or zinc, and has been previously burnt or calcined, the mixture of salt and pul-
verized ore may be at once subjected to a bright red heat, the volatilized
chlorides passing into the condensing apparatus are condensed-with water.
The ore is withdrawn from the furnace whenever it ceases to smoke strongly,
and if any copper or other metal still remains in the calcined ore, it is only neces-
sary to wash it with the hot acid solution that runs from the tower or con-
densing apparatus; by these means the last trace of copper or other metal is
readily extracted. The copper or other metal is obtained from these solutions
by precipitation with iron, lime, or an alkali, and the sulphate of soda may be
afterwards obtained by evaporation and crystallization.
When a mixed ore is under treatment containing metals whose chlorides
volatilise at different temperatures far removed, such as copper and tin, copper
or zinc and arsenic, lead and antimony, I employ a furnace with two or more
beds, all heated by the same fire or fires, each bed having a separate condenser.
By these means the arsenic, tin, or antimony are volatilised in the upper or
colder beds, and separately condensed, and the copper, lead, or zinc in the
lower and hotter beds.

page_text: The third class of ores I treat exactly as the second class, the silica taking
the place of the sulphur, and decomposing the salt at a red heat. When the
proportion of salt used is below 30 per cent., the heat may be at once urged to
and sustained at a bright red heat. When an ore is deficient in sulphur and
contains a large proportion of oxide of iron, such as the calcined or burnt
pyrites or mundics containing copper, silver, and other metals, and from which
nearly all the sulphur has been removed for the manufacture of sulphuric acid,
I find that the addition of 5 or 10 per cent. of a strongly siliceous ore very
much assists and hastens the decomposition. The proportion of salt to be used
very much depends upon the composition of the ores. Unless sulphur exists
in very large proportion, twice as much common salt as metal to be extracted
is, I find in practice, a very safe quantity to use as a general rule. When the
proportion of copper in the burnt pyrites or siliceous. ores.exceeds 3 per
cent., it is not economical to keep it too long in the furnace; I therefore with,
draw it from the furnace as soon as I find that all the copper has been con-
verted into chloride or subchloride of copper. Whilst the ore is still hot, I
immerse it in the acid liquor from the tower or condenser, with the addition of
a little muriatic acid; about cwt. to the ton of ore, which will remove the
last traces of copper at once.
.
For the sake of clearness in the description of the. methods. I pursue..to
obtain the metals from their ores, I have principally mentioned the ores, of
copper; but I would have it to be. distinctly understood that I claim the ex-
tension of the sulphuric acid process to the ores of zinc and several other
metals, and the process for subliming the chlorides to the poor ores of all.
metals whose chlorides are volatile at any degree of heat. I am aware that
both sulphuric acid and common salt have been used in various ways for the
purpose of extracting the metals from their ores, therefore I do not claim the
use of these materials. Heretofore the great objection to the use of salt has
been the loss of the metals through sublimation, if the heat was not very
carefully managed and kept very low; the process was therefore slow and
imperfect. By the processes I have described these evils have been re-
medied. So, in like manner, the cost of sulphuric acid has been heretofore
so very great, that the economical extraction of copper or zinc from their ores
has been rendered impossible; whereas by the processes I have described, one
ton of brimstone made into acid, extracts from 10 to 15 tons of metallic copper
from its ores.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that I claim,―
First, the method or methods herein described for the extraction of copper

page_text: zinc, silver, cobalt, and several other metals from their ores by means of
sulphuric acid.
Second, the methods herein described for obtaining oxide of copper, oxide
of zinc, and other analogous metals from the anhydrous sulphates of zinc,
copper, and other metals.
Third, the method or methods herein particularly described for obtaining
metallic copper, lead, zinc, or other analogous metal from their dried
sulphates
Fourth, the method or methods herein particularly described of obtaining,
recovering, or reproducing the sulphuric acid contained in the dried sulphates
of copper, lead, zinc, and other metals.
Fifth, the separation of silver, cobalt, and other metals from copper, zinc,
and other metals by the means and in the several ways herein particularly.
described.
Sixth, the separation of copper, silver, and all other metals whose chlorides
are more or less volatile, by calcining their ores in close furnaces or retorts
in connection with condensers at a high heat, whereby the metal or metals con-.
tained in their ores are in a short space of time converted into chlorides
which sublime and are condensed, or remain in the furnace or retort, and are
soluble in water or water slightly acidulated with muriatic acid.
And, lastly, the separation of metals. from each other whose chlorides
volatilise at degrees of heat far removed, by calcining them in a furnace,
with salt, the furnace having two or more beds, and each bed having a separate
condenser.
In witness whereof, I, the said. William Henderson, have hereunto set
my hand and seal, this Eighteenth day of June, One thousand eight
W*. HENDERSON. (L.S.)