IMPROVEMENTS IN TREATING ORES CONTAINING SILVER AND CERTAIN OF ITS COMPOUNDS, COPPER AND CERTAIN OF ITS COM- POUNDS, LEAD AND CERTAIN OF ITS COMPOUNDS, EITHER SEVERALLY OR COMBINED, AND REDUCING AND EXTRACTING EXPEDITIOUSLY EACH OR ANY OF THESE METALS THEREFROM AND SEPARATING THEM.
Year: 1877

page_text: LETTERS PATENT to Farnham Maxwell Lyte, of the Scientific Club, Savile
Row, in the County of Middlesex, and at present of Paris, in the Republic of
France, for the Invention of "IMPROVEMENTS IN TREATING ORES CONTAINING
SILVER AND CERTAIN OF ITS COMPOUNDS, COPPER AND CERTAIN OF ITS COM-
POUNDS, LEAD AND CERTAIN OF ITS COMPOUNDS, EITHER SEVERALLY OR
COMBINED, AND REDUCING AND EXTRACTING EXPEDITIOUSLY EACH OR ANY
OF THESE METALS THEREFROM AND SEPARATING THEM.'
"
PROVISIONAL SPECIFICATION left by the said Farnham Maxwell Lyte at
the Office of the Commissioners of Patents on the 23rd July 1877.
FARNHAM MAXWELL LYTE, of the Scientific Club, Savile Row, in the County of
Middlesex, and at present of Paris, in the Republic of France. "IMPROVEMENTS IN
TREATING ORES CONTAINING SILVER AND CERTAIN OF ITS COMPOUNDS, COPPER AND
CERTAIN OF ITS COMPOUNDS, LEAD AND CERTAIN OF ITS COMPOUNDS, EITHER
SEVERALLY OR COMBINED, AND REDUCING AND EXTRACTING EXPEDITIOUSLY EACH
OR ANY OF THESE METALS THEREFROM AND SEPARATING THEM."
This Invention relates to improvements in treating ores containing silver and
certain of its compounds, copper and certain of its compounds, lead and certain of
its compounds, either severally or combined, and reducing and extracting expe-
ditiously each or any of these metals therefrom and separating them.
I proceed as follows:-The ore is first pulverized and calcined if requisite to expel
any large proportions of sulphur or arsenic it may contain. It is now to be
thoroughly wetted with sulphuric acid; the sulphuric acid should be in such
quantity as to ensure the saturation of all the metals and earthy bases present, and
leave some excess of acid. The mixture is now to be heated in an oven, stove, or
hot chamber, until all the silver or other metals to be extracted have become
converted into sulphates.

page_text: The operation will generally be found to be complete when the heavy white
fumes of sulphuric acid which are at first disengaged begin to diminish.
Acid sulphates, such as the acid sulphates of soda or of potash, may be employed
in place of sulphuric acid as above, but usually these present no advantages over
the latter. At the end of the operation, which I will call "sulphatation," the material
will be found to have become more or less caked together. If necessary it may be
crushed. It is now to be placed in a vat and drenched with muriatic acid, enough
to chloridize the bases contained in the material which has been thus disintegrated
by the "sulphatation," and to leave a fair excess of acid. In this stage, instead of
employing muriatic acid to chloridize the bases as above mentioned, I find that the
use of a mixture of muriatic acid or of sulphuric acid with strong brine (solution of
chloride of sodium) is more advantageous, as it is both effective and economical, and
in presence of lead, such a mixture forms at the same time a most powerful solvent
for this metal, even for sulphate of lead.
In the separation of copper from lead I proceed as follows:-If sulphate or
chloride of lead be treated with strong brine only acidulated slightly with sulphuric
acid, or if the brine be acidulated with hydrochloric acid, the sulphate or chloride
of lead dissolves abundantly, especially with the aid of heat; but if the same
sulphate or chloride of lead be treated with an excess of sulphuric acid, to which
has been added just a little, say only 10 per cent., more or less, of saturated brine,
as compared to the quantity of sulphuric acid (S.O3) employed, or if an alkaline
sulphate be added to the solution in such proportion that there may be about 10 of
sulphuric acid (SO) to one of chlorine (CI) in the solution, it will be found to be
nearly if not quite insoluble therein. Now such a solution as the one last mentioned,
if sufficiently acid, dissolves copper abundantly. This then furnishes us with the
ineans of treating mixed ores containing lead and copper. After being pulverized
and calcined they are first treated with a solution of sulphuric acid, to which has
been added chloride of sodium only in such proportion as to dissolve the copper and
not the lead, and by subsequent treatinent with brine only acidulated with a
relatively small proportion of sulphuric acid, or, still better, with brine acidulated
with muriatic acid, say only 1 or 2 per cent. of strong acid, the whole of the lead
may be taken up.
One can arrive at a similar result and obtain a more complete solution of the
copper by treating the ore, whether previously sulphatized or simply calcined with
sulphuric acid, and leaving the mixture exposed to the air at ordinary tem-
peratures when the copper all becomes converted into sulphate, and can be washed
out, while lead and silver, if present, may be washed out of the residue with
acidulated brine. From these solutions the copper on the one hand may be thrown
down by metallic iron or zinc, and the lead and silver on the other in the brine by
zinc.
In order to keep all the silver in the precipitate with the lead, in this case it is
well to add a little brine to the sulphuric acid when poured over the ore. From
each of these solutions the lead and copper may be respectively precipitated by zinc,
according to well-known processes. There is no necessity for strictly adhering to
these proportions of brine to acid; a certain latitude is allowable; nor is it absolutely
necessary that brine (solution of chloride of sodium) should be used; other alkaline
and metallic chlorides have great solvent power for lead when acidulated, and
the contrary is the case when excess of sulphuric acid is present. Chloride
of silver, unlike lead, is on the contrary soluble in both acid and neutral brine.
I believe this is the first time that these reactions with lead salts and acid
chlorides have been observed, or even that the relative insolubility of chloride of
lead in neutral brine as compared with its great solubility in acidulated brine has
been mentioned.
I have only to add that the solvent powers of the acid brine are greatly
increased by heating, so I perform all this treatment, by preference, in tubs heated
by steam.

page_text: In case of treating an ore containing silver and no lead, it may be found con-
venient to add some lead, sulphate, or chloride, or a soluble lead salt before adding
the acid brine to the sulphatized ore. The silver then precipitates with the lead
when the metallic zinc is introduced. When treating ores by this method, much
sulphuric acid is liable to accumulate in the chloride of zinc and sodium solution
which remains; and if the zinc is to be extracted as rough zinc oxide by precipi-
tation with lime, the former will be found contaminated with calcium sulphate;
such a mixture cannot be conveniently distilled for the recovery of the zinc as
metallic zine. I therefore prefer first of all to precipitate the sulphuric acid as
calcium sulphate by adding some of the calcium chloride residue of a former
operation, and then after drawing off the clear solution of zinc chloride I proceed to
precipitate from it hot the rough zinc oxide.
The brine may be used over and over again, only being freshly acidulated when
requisite until it becomes so charged with zinc chloride that it may be thought
advisable to extract the zinc. This treatment with acidulated brine is applicable
to the treatment of lead sulphate and lead chloride residues from dye works, lead
ashes, &c.
After the above treatment, if an ore contained any gold, this will be found in the
gangue or matrix remaining after the process. It may be extracted either by
chemical means with aqua regia, muriatic acid, and peroxide of manganese, muriatic
acid, and bleaching powder, or any liquid generating or containing free chlorine, or
it may be separated by amalgamation, the silicious matter composing the residue
being peculiarly well prepared by this treatment for avoiding flouring and loss of
mercury.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Farnham Maxwell Lyte in the Great Seal Patent Office on the 22nd
January 1878.
FARNHAM MAXWELL LYTE, of the Scientific Club, Savile Row, in the County of
Middlesex, and at present of Paris, in the Republic of France.
"IMPROVEMENTS IN
TREATING ORES CONTAINING SILVER AND CERTAIN OF ITS COMPOUNDS, COPPER AND
CERTAIN OF ITS COMPOUNDS, LEAD AND CERTAIN OF ITS COMPOUNDS, EITHER
SEVERALLY OR COMBINED, AND REDUCING AND EXTRACTING EXPEDITIOUSLY EACH
OR ANY OF THESE METALS THEREFROM AND SEPARATING THEM."
This Inventiion relates to improvements in treating ores containing silver and
certain of its compounds, copper and certain of its compounds, lead and certain of
its compounds, either severally or combined, and reducing and extracting expe-
ditiously each or any of these metals therefrom, and separating them.
I proceed as follows:-The ore is first pulverized and calcined if requisite to expel
any large proportions of sulphur or arsenic it may contain. It is then to be
thoroughly wetted with sulphuric acid; the sulphuric acid should be in such
quantity as to ensure the saturation of all the metals and earthy bases present, and
leave some small excess of acid. The mixture is then to be heated in an oven,
stove, or hot chamber, until all the silver and other metals intended to be extracted
have become converted into sulphates.
The operation will generally be found to be complete when the heavy white
fumes of sulphuric acid which are at first disengaged begin to diminish.
Acid sulphates, such as the acid sulphates of soda or of potash, may be employed
in place of sulphuric acid as above, but usually these present no advantages over
the latter. At the end of this operation, which I will call "sulphatation," the
inaterial will generally be found to have become more or less caked together. If
necessary it should be crushed or broken up. If it should be found that the
sulphatation has not completely attacked the minerals, it will be found advantageous
to place the crushed material in a vat, and treat it with muriatic acid in sufficient
quantity to completely chloridize the metallic bases contained in the material, and
to leave a fair excess of acid.
"
In ordinary cases the material when prepared in the manner above mentioned by
sulphatation," will be found to be completely converted into sulphates, and it is
then treated directly with brine acidulated with muriatic acid.
I have found that contrary to the hitherto general belief of chemists, hot acidu-
lated brine is a most powerful solvent for salts of lead, even for sulphate of
lead.
In the separation of copper from lead I proceed as follows:-If sulphate or
chloride of lead be treated with strong brine, or if the brine be acidulated with
hydrochloric acid, the sulphate or chloride of lead dissolves abundantly, especially
with the aid of heat; but if the same sulphate or chloride of lead to be treated with
an excess of sulphuric acid, to which has been added just a little, say only 10 per
cent., more or less, of saturated brine, as compared to the quantity of sulphuric acid
(SO) employed; or if an alkaline sulphate be added to the solution in such pro-
portion that there may be about 10 of sulphuric acid (SO3) to one of chlorine (C1)
in the solution, the lead will be found to be nearly if not quite insoluble therein.
Now such a solution as the one last mentioned, if sufficiently acid, dissolves copper
abundantly. This then furnishes us with the means of treating mixed ores con-
taining lead and copper, by what I term a differential separating process. After
being pulverized and calcined they are first treated with a solution of sulphuric
acid, to which may be added, if silver be present, a little chloride of sodium. The
acid present should be in such proportion as to dissolve the copper and combine
with the lead. The cupreous solution is drawn off and the copper recovered in the
ordinary way. The remaining insoluble matter containing lead and silver is then
treated with brine acidulated with a relatively small proportion of sulphuric acid,

page_text: or still better, with brine acidulated with muriatic acid, say only 1 or two per
cent. of strong acid. The whole of the lead may be thus taken up.
A similar result might be obtained, attended with a more complete solution of the
copper, by treating the ore (whether previously sulphatized or simply calcined) with
sulphuric acid, and leaving the mixture exposed to the air at ordinary temperatures,
when the copper all becomes converted into sulphate, and can be washed out while
lead and silver, if present, may be dissolved out of the residue by treating it with
acidulated brine. From these solutions the copper on the one hand may be thrown
down by metallic iron or zinc, and the lead and silver dissolved in the brine may
be recovered by means of zinc, as described in the Specification of former Letters
Patent granted to me, dated the 15th day of February 1877.
In order to keep all the silver in the precipitate with the lead, in this case it is
well to add a little brine to the sulphuric acid when poured over the ore, as above
stated. From each of these solutions the lead and copper may respectively be
precipitated by zinc, as above mentioned. There is no necessity for strictly
adhering to these proportions of brine to acid, a certain latitude is allowable, nor is
it absolutely necessary that brine (solution of chloride of sodium) should be used;
other alkaline and metallic chlorides have great solvent power for lead when
acidulated, the solvent power being diminished or wholly taken away in proportion
as more or less sulphuric acid is present in excess. Chloride of silver, unlike lead, is
on the contrary soluble in both acid and neutral brine.
I believe this is the first time that these reactions with lead salts and acid
chlorides have been observed, or even that the relative insolubility of chloride of
lead in neutral brine, as compared with its great solubility in acidulated brine, has
been mentioned. Freshly precipitated chloride or sulphate of lead are however
sufficiently soluble in hot neutral non-acidulated brine for brine alone to be used.
I have only to add that the solvent powers of the acid brine are greatly increased
by heating, so I perform all this treatment, by preference, in tubs heated by
steam.
In case of treating an ore containing silver and no lead, it may be found con-
venient to add some lead, sulphate, or chloride, or a soluble lead salt, before adding
the acid brine to the sulphatized ore. The silver then precipitates with the lead
when the metallic zinc is introduced. When treating ores by this method, much
sulphuric acid is liable to accumulate in the chloride of zinc and sodium solution
which remains; and if the zinc is to be extracted as rough zinc oxide by precipi-
tation with lime, the former will be found contaminated with calcium sulphate.
Such a mixture cannot be conveniently distilled by the ordinary processes for the
recovery of the zinc as metallic zinc; I therefore find it advantageous to proceed as
follows: I first precipitate the sulphuric acid as calcium sulphate by adding some
of the calcium chloride residue of a former operation, and then after drawing off
the clear solution of zinc chloride, I proceed to precipitate from it hot the rough
zinc oxide.
The brine may be used over and over again, only being freshly acidulated when
requisite until it becomes so charged with zinc chloride, that it may be thought
advisable to extract the zinc. This treatment with acidulated brine is applicable to
the treatment of lead sulphate and lead chloride residues from dye works, lead
ashes, &c.
After the above treatment, if an ore contained any gold, the gold will be found
in the gangue or matrix remaining after the process. It may be extracted by any
well-known process, the silicious matter composing the residue being peculiarly well
prepared by my improved mode of treatment by means of acidulated brine.
Having described the nature of my Invention and the manner of performing the
Bame, I declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is,-
Firstly. My improved method of treating ores by the process of sulphatation,
followed by the use of acidulated (or in the case of freshly precipitated lead salts,
neutral) chloride solution, substantially as above described.

page_text: Secondly. The recovery of silver and lead from ores containing those metals by
the use of my improved method of treatment, substantially as herein described.
Thirdly. The employment of the differential separating process for treating ores
or mixtures containing lead and other metals, substantially as above described.
Fourthly. The removal of sulphuric acid from zinc chloride solutions contaminated
therewith by precipitating it in the manner and for the purpose, substantially as
above described.
In witness whereof, I, the said Farnham Maxwell Lyte, have hereunto set
my hand and seal, this First day of December, in the year of our Lord One
thousand eight hundred and seventy-seven.
F. MAXWELL LYTE. (L.S.)