IMPROVEMENTS IN THE TREATMENT OF ORES OF LEAD, IN THE THE SEPARATION OF METALS CONTAINED THEREIN, AND IN THE PRODUCTION OF SULPHURIC ACID
Year: 1875

page_text: LETTERS PATENT to Desmond Gerald Fitz-Gerald, of Loughboro' Road
North, in the County of Surrey, Electrician, for the Invention of
"IMPROVEMENTS IN THE TREATMENT OF ORES OF LEAD, IN THE SEPARATION OF
PROVISIONAL SPECIFICATION left by the said Desmond Gerald
Fitz-Gerald at the Office of the Commissioners of Patents, with
his Petition, on the 9th July 1875.
I. DESMOND GERALD FITZ-GERALD, of Loughboro' Road North, in
the County of Surrey, Electrician, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE TREATMENT OF ORES OF LEAD, IN
THE SEPARATION OF METALS CONTAINED THEREIN, AND IN THE PRODUCTION OF
SULPHURIC ACID," to be as follows :—
The chief objects of my Invention are the complete separation of
lead, silver, copper, and gold, when two or more of these metals are
present in the ore, the production of pure or nearly pure chloride of
lead and the utilization of the sulphuric acid radicle formed, when

page_text: galena ores and certain other sulphides are roasted or otherwise
oxidized.
As an example of one process I roast galena sufficiently to convert
into sulphate a considerable portion of the lead existing in it, and I
lixiviate, if necessary, in order to separate any soluble sulphates; I
then heat the residual ore with concentrated hydrochloric acid in a close
vessel; sulphide of hydrogen is evolved which I utilize by bringing it
into contact with a second portion of roasted ore, moistened or held in
suspension in water; sulphuric acid being thus produced by the reaction
between sulphide of hydrogen and sulphate of lead (or of copper).
The hydrochloric acid converts the lead sulphate and the residual
lead sulphide in the first portion of ore into chloride of lead, dissolving
a portion of the latter and liberating sulphuric acid. It also converts
sulphide of silver into chloride of this metal which it dissolves. The
silver may at once be precipitated in the metallic form by bringing the 1
hydrochloric acid solution into contact with metallic copper; but I
prefer to accumulate the silver in solution and to obtain it as chloride
when the hydrochloric acid is regenerated, as herein-after described.
The hot hydrochloric acid solution is passed through a filtering appa-
ratus into a vessel or tank in which pure chloride of lead is deposited
as the solution cools. Another charge of hydrochloric acid (from which
chloride of lead has deposited) is now pumped through a worm which
traverses the hot solution into the vessel containing the ore. Two or
more charges of acid are thus used alternately and repeatedly in similar
manner to economise heat and time.
After the hydrochloric acid has been repeatedly digested upon the
roasted ore, and when a considerable proportion of sulphuric acid has
thus been liberated, I obtain or utilize the latter acid by distilling hydro-
chloric acid from the mixture, cither without any addition to it or after
the addition of a suitable proportion of common salt. In the latter
case the sulphuric acid is utilized in the production of sulphate of
soda, whilst a quantity of hydrochloric acid equivalent to that abstracted
by the deposition of chloride of lead within the depositing vessels or
tanks is reproduced. The hydrochloric acid vapours are passed through
vessels similar in construction to the apparatus commonly known as ‹
Woolfe's bottles, charged with water or with dilute hydrochloric acid,
such as is obtained at the close of the distillation; or these vapours

page_text: may be condensed within a coke tower, as is well understood. Chloride
of silver, chloride of lead, sulphate of lead, and other salts which may
have been produced by the action of the acid upon the ore, are deposited
from the solution left within the retort after the separation of the
hydrochloric acid.
The insoluble salts, if obtained together, may be separated from each
other by successive treatment with hot water and solution of ammonia
or of common salt; but by the use of suitable precautions they may be
obtained separately by consecutive depositions.
The above process may be varied by roasting or treating the ore so as
to obtain oxide as well as sulphate of lead, extracting the former with an
acid forming with it a soluble salt, and acting upon the residue with
hydrochloric acid, as herein-before described.
If the ore contains gold this metal is left in the residue from the ore
after extraction of the lead, silver, and other metals acted upon by this
acid which may be present and may be obtained by adding to this
residue a small quantity of any suitable oxidant, such as red lead,
plumbic acid, or oxide of manganese, and repeating the digestion with
a small quantity of hydrochloric acid. The gold thus obtained as
ohloride may be reduced by means of sulphurous acid, a protosalt of
iron, or other known means.
I also utilize hydrochloric acid in the manufacture of sulphuric acid
in concentrating argentiferous sulphide ores, and in obtaining chloride
of lead in the following manner:-I roast a sulphide ore of lead or
| copper in such manner as to convert the metal into sulphate, adding in
some cases pyrites to the ore to ensure a more complete conversion.
The roasted ore (or the metallic sulphate in a purer form) is treated with
sulphide of hydrogen in presence of water, and is thus reconverted into
sulphide with liberation of sulphuric acid.
The sulphide of hydrogen may be obtained by the action of hot
bydrochloric acid upon galena, in which case chloride of lead is formed
which may be extracted by hot water; or other metallic sulphides
which are attacked by hydrochloric acid may be treated therewith for
the production of the hydrogen sulphide.
The metallic sulphide obtained may again be converted into sulphate
by roasting, and again be utilized in effecting the exchange of hydro-

page_text: chloric acid for its equivalent of sulphuric acid. I also generate sulphide
of hydrogen for the production of acids in the above and in other
analagous processes by acting upon metallic sulphides with steam or
with hydrocarbon gases or vapours at a high temperature.
SPECIFICATION in pursuance of the conditions of the Letters Patent ↓
filed by the said Desmond Gerald Fitz-Gerald in the Great Seal
Patent Office on the 8th January 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DESMOND
GERALD FITZ-GERALD, of Loughboro' Road North, in the County of
Surrey, Electrician, send grecting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of July, in the year of our
Lord One thousand eight hundred and seventy-five, in the thirty-ninth
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Desmond Gerald Fitz-Gerald, Her special
licence that I, the said Desmond Gerald Fitz-Gerald, my executors, admi-
nistrators, and assigns, or such others as I, the said Desmond Gerald
Fitz-Gerald, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might
make, use, exercise, and vond, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN THE TREATMENT OF ORES OF LEAD, IN THE SEPARATION OF
METALS CONTAINED THEREIN, AND IN THE PRODUCTION OF SULPHURIC ACID," upon
the condition (amongst others) that I, the said Desmond Gerald Fitz-
Gerald, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should parti-
cularly 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 Desmond Gerald Fitz-Gerald, do
hereby declare the nature of my said Invention, and in what manner

page_text: the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
The chief objects of my Invention are the complete separation of
lead, silver, copper, and gold, when two or more of these metals are
present in the ore, the production of pure or nearly pure chloride of
lead and the utilization of the sulphuric acid radicle formed, when
galena ores and certain other sulphides are roasted or otherwise
oxidised.
As an example of my process I roast galena sufficiently.to convert
into sulphate a considerable portion of the lead existing in it, and I
lixiviate, if necessary, in order to separate any soluble sulphate; I then
heat the residual ore with concentrated hydrochloric acid in a close
vessel. Sulphide of hydrogen is evolved, which I utilize by bringing it
into contact with a second portion of roasted ore, moistened or held in
suspension in water. Sulphuric acid being thus produced by the reaction
between sulphide of hydrogen and sulphate of lead (or of copper).
The hydrochloric acid converts the lead sulphate and the residual
lead sulphide in the first portion of ore into chloride of lead, dissolving
a portion of the latter and liberating sulphuric acid. It also converts
sulphide of silver into chloride of this metal which it dissolves. The
silver may at once be precipitated in the metallic form by bringing the
hydrochloric acid solution into contact with metallic copper; but I
prefer to accumulate the silver in solution and to obtain it as chloride
when the hydrochloric acid is regenerated, as herein-after described.
The hot hydrochloric acid solution is passed through a filtering appa-
ratus into a vessel or tank in which pure chloride of lead is deposited
as the solution cools. Another portion of hydrochloric acid (from which
chloride of lead has deposited) is now pumped through a worm which
traverses the hot solution into the vessel containing the ore. Two or
more charges of acid are thus used alternately and repeatedly in similar
manner to economize heat and time.
After the hydrochloric acid has been repeatedly digested upon the
roasted ore, and when a considerable proportion of sulphurio acid has
thus been liberated, I obtain or utilize the latter acid by distilling hydro-
¡ chloric acid from the mixture, either without any addition to it or after
the addition of a suitable proportion of common salt; or a solution of
common salt may be added to the hydrochloric acid in the first stage

page_text: 1
'
of the process. In the latter cases the sulphuric acid is utilized in
the production of sulphate of soda, whilst a quantity of hydrochloric
acid equivalent to that abstracted by the deposition of chloride of lead
within the depositing vessels or tanks is reproduced. The hydrochloric
acid vapours are passed through vessels similar in construction to the
apparatus commonly known as Woolf's bottles, charged with water or
with dilute hydrochloric acid, such as is obtained at the close of the dis-
tillation; or these vapours may be condensed within a coke tower, as is
well understood. Ohloride of silver, chloride of lead, sulphate of lead,
and other salts which may have been produced by the action of the acid:
upon the ore are deposited from the solution left within the retort after
the separation of the hydrochloric acid.
.
The insoluble salts if obtained together may be separated from each
other by successive treatment with hot water and solution of ammonia
or of common salt, but by the use of suitable precautions they may be
obtained separately by consecutive depositions.
The above process may be varied by roasting or treating the ore so as
to obtain oxide as well as sulphate of lead, extracting the former with
an acid, forming with it a soluble salt, and acting upon the residue with
hydrochloric acid as herein-before described.
If the ore contains gold, this metal is left in the residue from the ore
after extraction of the lead, silver, and other metals acted upon by this
acid which may be present, and may be obtained by adding to [this
residue a small quantity of any suitable oxidant, such as red lead,
plumbic acid, or oxide of manganese, and repeating the digestion with
a small quantity of hydrochloric acid. The gold thus obtained as
chloride may be reduced by means of sulphurous acid, a protosalt of
iron, or other known means.
I also utilize hydrochloric acid in the manufacture of sulphuric acid,
in concentrating argentiferous sulphide ores, and in obtaining chloride
of lead in the following manner:-I roast a sulphide ore of lead or
copper in such manner as to convert the metal into sulphate, adding
in some cases. pyrites to the ore to ensure a more complete conversion.
The roasted ore (or the metallic sulphate in a purer form) is treated with
sulphide of hydrogen in presence of water, and is thus re-converted into
-sulphide-with liberation of sulphuric acid.
..

page_text: The sulphide of hydrogen may be obtained by the action of hot
hydrochloric acid upon galena, in which case chloride of lead is formed,
which may be extracted by hot water; or other metallic sulphides
which are attacked by hydrochloric acid may be treated therewith for
the production of the hydrogen sulphide.
The metallic sulphide obtained may again be converted into sulphate
by roasting, and again may be utilized in effecting the exchange of
hydrochloric acid for its equivalent of sulphuric acid.
I also generate sulphide of hydrogen for the production of acids in
the above and in other analogous processes by acting upon metallic
sulphides with steam or with hydrocarbon gases or vapours at a high
temperature.
Having thus fully described my said Invention and the manner
performing the same, I wish it understood that I claim,―
of
First. The treatment of roasted or oxidised (or partially roasted or
oxidised) ores of lead with hot hydrochloric acid alone or in conjunction
with common salt, whereby I effect the separation of the metals con-
tained therein and the production or utilization of the liberated sulphuric
acid as herein described.
Second. The utilization of the sulphide of hydrogen generated by
treating partially roasted (sulphide) ores of lead with hot hydrochloric
acid, or by treating the unroasted ores in a similar manner in the pro-
duction of sulphuric acid from sulphate of lead or of copper contained
in roasted ores of these metals or obtained from other sources as herein
described.
In witness whereof, I, the said Desmond Gerald Fitz-Gerald, have
hereunto set my hand and seal, this Seventh day of January, in
the year of our Lord One thousand eight hundred and seventy-
: