IM- PROVEMENTS IN PROCESSES OR MEANS EMPLOYED FOR SEPARATING OR EXTRACTING SILVER OR OTHER METALS FROM LEAD
Year: 1863

page_text: LETTERS PATENT to George Henry Birkbeck, of the Firm of Tongue &
Birkbeck, of 34, Southampton Buildings, Chancery Lane, in the County
of Middlesex, Patent Agents & Engineers, for the Invention of "IM-
PROVEMENTS IN PROCESSES OR MEANS EMPLOYED FOR SEPARATING OR EXTRACTING
SILVER OR OTHER METALS FROM LEAD."-A communication from abroad by
M. Clement Roswag, Engineer, of Paris, in the Empire of France.
Sealed the 31st July 1863, and dated the 13th February 1863.
PROVISIONAL SPECIFICATION left by the said George Henry Birkbeck
at the Office of the Commissioners of Patents, with his Petition, on
the 13th February 1863.
I, GEORGE HENRY BIRKBECK, of the Firm of Tongue & Birkbeck, of
84, Southampton Buildings, Chancery Lane, in the County of Middlesex,
Patent Agents & Engineers, do hereby declare the nature of the Invention
for "IMPROVEMENTS IN PROCESSES OR MEANS EMPLOYED FOR SEPARATING OR EX-
TRACTING SILVER OR OTHER METALS PROM LEAD," to be as follows:-
This Invention relates to improvements in processes or means employed for
separating or extracting silver from lead, described in the Final Specification
of an Invention for which Letters Patent were granted to me, bearing date
October 23rd 1861, No. 2643.
The present improvements comprise three new modifications of the processes
formerly described, and consist,
First, in the manipulation or "working" of the dross.

page_text: Secondly, in means for economizing the zinc employed in the processes.
And, thirdly, in the application of the processes or means to the extraction
of gold from alloys of gold bearing lead, or of gold and silver bearing lead.
The first modification, relating to the manipulation, refers to the operation
of working the dross containing silver and zinc, or the transformation of the
alloy of zinc containing silver into lead containing silver capable of cupellation.
This part of the Invention consists essentially in the employment of a bath of
sulphuric acid of suitable strength, for the purpose of dissolving the whole or a
large proportion of the zinc contained in the silver bearing ashes. The
residues, after washing and settling, are by preference moulded into bricks
by bydraulic pressure. These bricks are treated in the furnace like silver
bearing ashes, or they may be passed directly to the cupel furnace if the
workmen who manage the furnace are sufficiently skilful. This operation is
not indispensible, but it has the advantage of rendering the process of working
the ashes more rapidly, and of diminishing the loss of silver caused by
want of care on the part of the workman. The burning of the zinc alloyed
with lead and silver, especially when the zinc predominates (which is the case
with very rich lead) causes considerable loss, which may be avoided by proper
care, but it is necessary to raise the temperature of the furnace to "cherry-red"
heat, not touching the mass before having allowed it to cool of itself, or the
furnace may be cooled easily and rapidly by throwing some small coal, damped
with water, on to the fire. The fire may be revived very quickly when required
by clearing the bars, or raking the fire with a pointed picker. The employment
of the bath of sulphuric acid is preferable to that of muriatic acid, because of
the formation of chloride of silver, which is difficult to decompose by heat
without loss. The bath of sulphuric acid, on the other hand, gives place to
water charged with sulphate of zinc, and gives it up at a profit on the cost of
the process in case of any demand in the locality for this sulphate. In the
absence of such demand it can be converted into oxide of zinc, if it is more
marketable.
The second part of the improvements relates to the economy of the zinc
employed, and consists in restoring to the desilvering boiler for the subsequent
operations a certain quantity of zinc bearing lead, that is to say, lead susceptible
on account of its small proportion of silver and its great proportion of zinc, to
take off a part of the silver or lead of the said boiler. The zinc bearing lead
is derived from two sources; first, from the process of eliquation, and secondly,
from the first skimmings of the softening or annealing which precedes this
eliquation, the skimmings being made before the oxydation of the zinc. The
economy obtained by the introduction of the zine bearing lead of these two

page_text: operations in the boiler for desilvering is about thirty per cent. of the zinc
which it is found necessary to employ.
The following process is applicable to leads of very low quality, by sub-
mitting them to two or three crystallizations:- For leads containing 02 per
cent. of silver (for example) greater economy is produced in the cost of re-
working to crystallize them, and to treat the rich lead with zinc; these last,
after having been impoverished in that manner, re-enter into crystallization,
which effects the total elimination of the zinc in the lead ready for sale in case
the purification may not have been complete by means of the annealing
process. There is equal economy in the cost of reviving by previously submitting
to crystallization leads which are very rich; for example, those containing
about 3 per cent. or more, and treating the impoverished lead with zinc by
this process. The crystallization is maintained upon the saleable lead obtained
to ensure the complete elimination of the zinc. This result corresponds with
that which reduces the crystallization to a small number of operations, and is
very economical.
Lastly, this Invention is applicable with advantage to the extraction of gold
from alloys of gold bearing lead, or of gold and silver bearing lead arising,
for example, from the treatment of rich copper ore or of ingots; the extraction
of gold and of silver combined, or of gold alone, is made with very great
rapidity on the same principles and under the same conditions employed
for silver only.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Henry Birkbeck in the Great Seal Patent Office on
the 18th August 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
HENRY BIRKBECK, of the Firm of Tongue and Birkbeck, of 34, Southampton
Buildings, Chancery Lane, in the County of Middlesex, Patent Agents and
Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of February, in the year of
our Lord One thousand eight hundred and sixty-three, in the twenty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said George Henry Birkbeck, Her special licence that 1, the
said George Henry Birkbeck, my executors, administrators, and assigns, or
such others as I, the said George Henry Birkbeck, my executors, administrators,

page_text: 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 PROCESSES OR MEANS EMPLOYED FOR SEPARATING
OR EXTRACTING SILVER OR OTHER METALS FROM LEAD," a communication to me
from abroad by M. Clement Roswag, Engineer, of Paris, in the Empire of
France, upon the condition (amongst others) that I, the said George Henry
Birkbeck, my executors or administrators, 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 George Henry Birkbeck, do hereby
declare the nature of the 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:-
This Invention relates to improvements in processes or means employed for
separating or extracting silver from lead, described in the Final Specification
of an Invention for which Letters Patent were granted to me bearing date
October 23rd 1861, No. 2643.
The present improvements comprise three new modifications of the processes
therein described, and consist, first, in the manipulation or "working of the
dross; secondly, in means for economizing the zinc employed in the processes;
and, thirdly, in the application of the processes or means to the extraction of
gold from alloys of gold bearing lead, or of gold and silver bearing lead.
The first modification relating to the manipulation refers to the operation of
working the dross containing silver and zinc, or the transformation of the
alloy of zinc containing silver into lead containing silver capable of cupel-
lation. This part of the Invention consists essentially in the employment of
a bath of sulphuric acid of about 20 degrees, or other suitable strength, for the
purpose of dissolving the whole, or a large proportion of the zinc contained in
the silver bearing ashes. The residues after washing and settling are, by pre-
ference, moulded into bricks by hydraulic pressure. These bricks are treated
in the furnace like the silver bearning ashes, or they may be passed directly to
the cupel furnace, if the workmen who manage the furnace are sufficiently
skilful. This operation is not indispensable, but it has the advantage of
rendering the process of working the ashes more rapidly, and of diminishing the

page_text: risk of loss of silver caused by want of care on the part of the workman.
The burning of the zinc alloyed with lead and silver, especially when the zinc
predominates (which is the case with very rich lead), causes considerable loss,
which may be avoided by proper care, but it is necessary to raise the tem-
perature of the furnace to "cherry-red heat," not touching the mass before
having allowed it to cool of itself, or the furnace may be cooled easily and
rapidly by throwing some small coal damped with water on to the fire. The
fire may be revived very quickly, when required, by clearing the bars or raking
the fire with a pointed picker. The employment of the bath of sulphuric acid
is preferable to that of muriatic acid, because of the formation of chloride of
silver, which is difficult to decompose by heat without loss. The bath of
sulphuric acid on the other hand gives place to water charged with sulphate
of zinc, and gives it up at a profit on the cost of the process, in case of any
demand in the locality for this sulphate. In the absence of such demand it
can be converted into oxide of zinc, if it is more marketable.
The second part of the improvements relates to the economy of the zinc
employed, and consists in restoring to the desilvering boiler for the subsequent
operations a certain quantity of zinc bearing lead, that is to say, lead sus-
ceptible on account of its small proportion of silver and its great proportion of
zinc to take up a part of the silver or lead of the said boiler. The zinc bearing
lead is derived from two sources, first, from the process of eliquation, and,
secondly, from the first skimmings of the softening or annealing, which
precedes this eliquation, the skimmings being made before the oxydation of the
zinc. The economy obtained by the introduction of the zinc bearing lead
of these two operations in the boiler for desilvering is about thirty per cent.
of the zinc, which it is found necessary to employ.
The following process, constituting the third part of the improvements, is
applicable to leads of very low quality by submitting them to two or three
crystallizations. For leads containing 02 per cent. of silver (for example),
greater economy is produced in the cost of reworking to crystallize them, and
to treat the rich lead with zinc; these last, after having been impoverished in
that manner, re-enter into crystallization, which effects the total elimination of
the zinc in the lead ready for sale in case the purification may not have been
completed by means of the annealing process. There is equal economy in the
cost of reviving by previously submitting to crystallization leads which are very
rich, for example those containing about 3 per cent. or more, and treating the
impoverished lead with zinc by this process. The crystallization is main-
tained upon the saleable lead obtained to ensure the complete elimination of

page_text: the zinc. This result corresponds with that which reduces the crystallization
to a small number of operations and is very economical.
Lastly, this Invention is applicable with advantage to the extraction of gold
from alloys of gold bearing lead, or of gold and silver bearing lead arising, for
example, from the treatment of rich copper ore. or of ingots, the extraction of
gold and of silver combined, or of gold alone, is made with very great rapidity
on the same principles and under the same conditions as employed for silver
only.
In witness whereof, I, the said George Henry Birkbeck, have hereunto
set my hand and seal, the Tenth day of August, in the year of our
Lord One thousand eight hundred and sixty-three.
G. H. BIRKBECK. (L.S.)