IMPROVEMENTS IN THE TREATMENT OF ORES OR METALLIC MIXTURES."
Year: 1880

page_text: LETTERS PATENT to Farnham Maxwell Lyte, of Putney, in the County of
Surrey, for an Invention of "IMPROVEMENTS IN THE TREATMENT OF ORES OR
METALLIC MIXTURES."
PROVISIONAL SPECIFICATION left by the said Farnham Maxwell Lyte
at the Office of the Commissioners of Patents on the 26th November 1880.
FARNHAM MAXWELL LYTE, of Putney, in the County of Surrey. "IMPROVEMENTS
IN THE TREATMENT OF ORES OR METALLIC MIXTURES."
This Invention relates to improvements in treating ores and metallic mixtures
of lead and zinc, or of lead and zinc with silver or copper founded in part upon
the improvements described in the Specifications of previous Patents granted to
me, and dated respectively February 15th 1877, No. 633, July 23rd 1877, No. 2807,
January 22nd 1879, No. 269, and March 10th 1880, No. 1051. In most cases the
whole line of treatment recommended or described in my former Patents is usually
the best, still as being applicable to certain classes of ores respectively referred to,
my present improvements relate to a method or process which is a possible, and in
some cases an advantageous modification of my previously described methods.
The main difference between the present Invention and those described in my said
former Patents consists in the use in combination with certain of my improved
processes of cold or slightly warm acid (by preference hydrochloric acid) in treating
the calcined ore instead of the hot hydrochloric acid I have generally recommended
heretofore, but I wish it to be understood that I do not specially claim the use of
acid, whether hot or cold. The acid treatment as used in my improved processes
of treating ores is merely a necessary preparatory application to the ore forming
one of the steps in the course of the general methods on which my previous Patents
are based, and I find that in some cases by using cold or slightly warm acid,
economy in the operation is the result.
When the ore is intended to be treated with cold or slightly warm acid, it is to
be first of all calcined, and for this method of treatment it is advantageous that
while the ore should be calcined as sweet as possible, it should not be calcined at
too high a temperature. The calcined ore is then to be digested in hydrochloric
acid. This acid need not contain above 15 to 20 per cent. of dry HCl, but the
strength may be varied. For the attack of the ore about half more than the

page_text: theoretical quantity for taking into solution the zinc, copper, and other soluble
bases will usually be found requisite, but this, as well as the strength of the acid to
be employed, may be settled first of all by experiment.
This digestion with the acid may be in some cases economically performed in the
cold, or at the temperature of the atmosphere for the time being, or after some
time the cold treatment may be assisted by heat, but during this digestion it must
be frequently agitated. According as the ore has been more or less carefully
calcined, or according to the nature of the ore, or the temperature at or the time
during which it is calcined, the zinc and all or part of the copper enter into
solution. I allow the liquor to settle, and by means of a successive and alternate
treatment, as prescribed in the Specification of my Patent, dated 22nd January 1879,
No. 269, I decant the liquor onto a batch of fresh ore, whereby it is more or less
perfectly neutralised, and most of the lead and silver it may have taken up is
reprecipitated. I allow the liquor containing the zinc and any copper that may be
present to settle clear, and then I draw it off, or it may be filtered. From this
liquor the copper and any traces of silver it may contain may be thrown down by
metallic iron, or the traces of lead, copper, and silver, by means of spelter or by
hydric sulphide or some soluble sulphide. The zinc oxide may be recovered from
the remaining liquor by the method prescribed in the Specification of my Patent,
No. 633, 15th February 1877, only that although as in said Patent, I precipitate
the zinc solution hot or boiling with milk of lime, and try as far as possible to only
add just enough lime to decompose the zinc chloride present. I prefer to err
rather on the side of a trifling excess of lime than of undecomposed zinc chloride,
and so I take care to carry my precipitation to such a point as to have present not
an excess of zinc chloride, as by mistake stated in Patent No. 633 above mentioned,
but rather a trifling excess of lime. I therefore so manage by continually testing
the liquor during the precipitation, that as soon as ever it shows the least trace of
excess of free lime in solution, all further addition of milk of lime shall be stopped.
It will be understood that the alternate continuous treatment is not a matter of
necessity so far as the exhaustion of the zinc contained in the ore is concerned, but
I prefer this method as being the most economical of acid, and as leaving the lead
and the silver to the utmost possible degree insoluble in the gangue, as shown in
the Specification of my Patent, No. 269, 22nd January 1879. Each gangue then
as it becomes exhausted of its zine, may be collected and treated by either of the
following methods:-
(1). In the dry way I smelt the residue with proper fluxes, and obtain the lead
and silver together. The volatility of the chlorides of lead and silver in this case
rather interferes with this mode of treatment. I however avoid to some extent
this difficulty by smelting with scrap iron, or by converting the chlorides into
sulphides before smelting, by treating the gangue together with the chlorides it
may contain with any alkaline or alkalino-earthy sulphide, say, even the tank
waste of alkali works, the alkaline or alkalino-earthy chloride formed by the
decomposition of the metallic chlorides being washed away previous to the smelting.
Or the lead and silver chlorides may be reduced in the gangue by means of spelter,
and be left mixed with it, the zinc chloride formed being washed out, and the whole
smelted together for lead and silver.
Inasmuch as generally the proportion of metal found in these residual gangues is
rather low, it is well to add to the charge some pure galena or some metallic lead;
these melt and collect the rest of the lead and silver, which otherwise might not
have been easily made to run together.
2nd. In the wet way I treat the residual gangue and metallic chlorides with
brine or an alkalino-earthy chloride, as described in the Specifications of my
Patents, No. 269, 22nd January 1879, and No. 1051, 10th March 1880, and the
lead and silver may be thus obtained.

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
26th May 1881.
FARNHAM MAXWELL LYTE, of Putney, in the County of Surrey. " IMPROVEMENTS
IN THE TREATMENT OF ORES OR METALLIC MIXTURES."
This Invention relates to improvements in treating ores and metallic mixtures of
lead and zinc, or of lead and zinc with silver or copper, founded in part upon the
improvements described in the Specifications of previous Patents granted to me
and dated respectively February 15th 1877, No. 633, July 23rd 1877, No. 2807,
January 22nd 1879, No. 269, and March 10th 1880, No. 1051. The processes or
methods of treatment recommended or described in the Specifications of my former
Patents work well and successfully when applied to the classes of ores respectively
referred to, and my present improvements relate to a method or process which is in
some cases an advantageous modification of my previously described methods. The
main difference between the present Invention and those described in the
Specifications of my said former Patents consists in the use, in combination with
certain of my improved processes of cold or slightly warm acid (by preference
hydrochloric acid) in treating the calcined ore instead of the hot hydrochloric acid
I have generally recommended bereto fore, but I wish it to be understood that I do
not make any separate claim to the use of acid whether hot or cold apart from its
use in the improved processes respectively invented and claimed by me as set forth
in my said Specifications. The acid treatment as used in my improved processes
of treating ores is merely a necessary preparatory application to the ore forming
one of the steps in the course of the general methods on which my previous
Patents are based, and I find that in some cases by using cold or slightly warm
acid instead of the hot acid previously specified, economy in the operation is the
result.
When the ore is intended to be treated with cold or slightly warm acid it is to
be first of all calcined, and for this method of treatment it is advantageous that
while the ore should be calcined as sweet as possible, it should not be calcined at
too high a temperature. The calcined ore is then finely ground and digested
in bydrochloric acid. This acid need not contain above 15 to 20 per cent. of
dry HCl, but the strength may be varied. For the attack of the ore about half
more than the theoretical quantity for taking into solution the zinc, copper, and
other soluble bases will usually be found requisite, but this as well as the strength
of the acid to be employed will depend on the quality of the ore, and may be
settled first of all by experiment on a small sample in the laboratory. This
digestion with the acid may be in some cases economically performed in the cold or
at the temperature of the atmosphere for the time being, or after some time the
cold treatment may be assisted by heat, but during this digestion it must be
frequently agitated. According as the ore has been more or less carefully calcined,
or according to the nature of the ore, or the temperature at which it has been
calcined, or the completness of the calcination, the zinc and all or part of the
copper enter into solution. I allow the liquor to settle, and by means of a
successive and alternate treatment as prescribed in the Specification of my Patent,
dated 22nd January 1879 (No. 269), I decant the liquor onto a batch of fresh ore,
whereby it is more or less perfectly neutralized, and most of the lead and silver it
may have taken up is reprecipitated. I allow the liquor containing the zinc and any
copper that may be present to settle clear, and then I draw it off; or it may be
filtered; some of the ground ore itself placed in a vessel with a false bottom may

page_text: be used as a filter for the purpose. From this liquor the copper and any traces of
silver it may contain may be thrown down by metallic iron, or the traces of lead,
copper, and silver, by means of spelter, or by hydric sulphide, or some soluble
sulphide. This is however scarcely necessary except when much copper be present
at scarcely more than the merest trace of either silver or lead passes into solution.
The zinc oxide may be recovered from the remaining liquor by the method
prescribed in the Specification of my Patent, No. 633, 15th February 1877, only
that although, as in said Patent I precipitate the zinc solution hot or boiling with
milk of lime, and try as far as possible to only add just enough lime to decompose
the zinc chloride present, I prefer to err rather on the side of a trifling excess of
lime than of undecomposed zinc chloride, and care should therefore be taken not to
carry the precipitation to such a point as to have present an excess of zinc chloride,
but rather a trifling excess of lime. I therefore so manage by continually testing
the liquor during the precipitation, that as soon as ever it shows the least trace
of excess of free lime in solution, all further addition of milk of lime shall be
stopped.
It will be understood that the alternate continuous treatment is not a matter of
necessity so far as the exhaustion of the zinc contained in the ore is concerned, but
I prefer this method as being the most economical of acid, and as leaving the lead
and the silver to the utmost possible degree insoluble in the gangue, as shown in
the Specification of my Patent, No. 269, 22nd January 1879. Each gangue then
as it becomes exhausted of its zinc, may be collected and treated by either of the
following methods :—
(1.) In the dry way I smelt the residue with proper fluxes and obtain the lead.
and silver together. The volatility of the chlorides of lead and silver in this case
rather interferes with this mode of treatment. I however avoid to some extent this
difficulty by first washing out as far as possible the acid zinc chloride, and then
smelting with scrap iron, or by convertiag the chlorides into sulphides before
smelting by treating the gangue together with the chlorides it may contain with
any alkaline or alkalino-earthy sulphide, say, even the tank waste of alkali works,
the alkaline or alkalino-earthy chloride formed by the decomposition of the metallic
chlorides, as well as any other soluble chlorides, being washed away previous to the
smelting. Or the lead and silver chlorides may be reduced in the gangue by means
of spelter, and be left mixed with it, the zinc chloride formed being washed out,
and the whole smelted together for lead and silver.
Inasmuch as generally the proportion of metal found in these residual gangues is
rather lower, it is well to add to the charge some pure galena or some metallic lead ;
these melt and collect the rest of the lead and silver, which otherwise could not
have been easily made to run together.
(2.) Proceeding in the wet way I treat the residual gangue and metallic
chlorides with brine or a solution of an alkalino-earthy chloride as described in the
Specifications of my Patents, No. 269, 22nd January 1879, and No. 1051,
10th March 1880, and the lead and silver may be thus obtained.
When, however, the method of treatment with cold acid is employed, certain
modifications may be introduced with a view to convenience and economy in the
plant described in the Specifications of my Patents, No. 269, 22nd January 1879,
and No. 1051, 10th March 1880. It should, however, be understood, nevertheless,
that the processes referred to can be worked completely, whether with cold or hot
acid, with the plant described in my said former Specifications. The method of
raising the attacking tubs with the ram or lift, which is specially advantageous for
the purpose of carrying out the decantations requisite during the course of the
alternate methodical treatment when very hot or boiling acid liquors have to be
decanted from one attacking tub into another, becomes, however, no longer
necessary, and may, if desirable, be supplanted by more ordinary methods. The
very hot or boiling liquors could not be pumped, syphoned, or blown over by an
injector (blow-jack), but when working with the cold or tepid solutions obtained

page_text: by the plan I now propose to employ, this can be managed easily; consequently,
for these decantations a pump injector, syphon, or any other convenient form of
apparatus, may be used instead of the system which I have heretofore recommended
of changing the respective levels of the tubs by raising one of them or lowering
the other. The same precautions as are recommended in the Specifications of my
former Patents should be observed in order to avoid as far as possible the
introduction of foreign metals in the form of piping, pumps, syphons, or otherwise,
into the acid zinc liquors, as these would tend to precipitate some of the silver and
prevent it from being taken up by the brine or saline solution afterwards. If,
however, any metal be used, lead is the one most to be recommended, as it soon
becomes coated with extraneous matters and oxidized and ceases to exert any
injurious action if not kept too long immersed in these cold solutions. As then the
decantations can be made with the above named implements I recommend for this
purpose the use either of a portable ebonite pump or of a portable injector
(blow jack) furnished with a suction pipe of embedded rubber suction hose and a
rubber delivery hose. The arrangement of the apparatus in such a manner as to
be able to transfer the pump or blow jack from attacking tub to attacking tub as
may be required is so obvious as to require no particular description, but the forms
and mode of adaptation of such apparatus will readily suggest themselves to any
one already familiar with chemical operations and wet metallurgical processes. It
will be advantageous in carrying out my improved processes to bear in mind that
in some cases the treatment of the brine or alkalino-earthy chloride solutions of
the lead and silver for the extraction of the silver by spongy or finely divided lead
may be performed by running these solutions over or through the said lead or by
any other means which can bring the solution into sufficiently intimate or prolonged
contact with sufficiently extended and sufficiently clean surfaces of lead. It is
little matter how the spongy or finely divided lead used for this purpose is
produced. It may be reduced by spelter from the solution in the brine or
alkalino-earthy chloride itself or may be produced by contact with a clean surface
of a lead cathode attached to a battery or dynamo-machine, or, as before stated,
fine lead wire or well prepared fleshly granulated lead may be used, but the spongy
lead reduced from the solution of the chloride, however produced, is preferable to
any other form, and the most active as a collector of silver, and though iron or
copper or other metals can be used, still I prefer the employmeut of lead to any
other metals for reasons stated in the Specifications of my former Patents above
referred to.
The contact of the argentiferous saline solution may be provided for, whether by
allowing it to flow over the surface or by making it percolate through the finely
divided lead, or by simple prolonged contact with the lead in the desilverizing
process, as already previously described. It is well, as recommended in my former
Specifications, that the saline solution should be reheated prior to or during its
contact with the lead. The surfaces of the lead are thus kept cleaner and the
extraction of the silver proceeds with more activity, the lead chloride which is
produced by the reduction of the silver chloride or other reducible chlorides which
may be present being prevented from forming a deposit on the lead and from thus
protecting it from further action. By cooling the saline solution the lead chloride
it may have taken up from the ore becomes in most part redeposited, and by
reheating after being decanted off the said solution regains its solvent power, for
lead chloride thus becoming capable of taking into solution any lead chloride
formed and maintaining the lead surfaces in a cleaner and more active condition.
It is the liability to become covered with extraneous matters and to become
oxidized superficially which renders it necessary that the lead employed should be
in a freshly prepared and finely divided state so as to present the most extended
surfaces possible to the saline solutions, and it is on this account not advisable to
attempt the employment of pig or even common sheet lead for the extraction of
the silver from these solutions.

page_text: Having now described my present improvements, and the manner of carrying
them into effect, I claim the use of the cold acid treatment as being simple and
economical in certain cases, substantially as herein described.
In witness whereof, I, the said Farnham Maxwell Lyte, have hereunto set my
hand and seal, this Twenty sixth day of May, in the year of our Lord
One thousand eight hundred and eighty one.
F. MAXWELL LYTE. (L.S.)