IMPROVEMENTS IN TREATING ORES AND MATERIALS CONTAINING ZINC, LEAD, SILVER, COPPER, IRON, AND IN SOME CASES ANTIMONY OR BISMUTH, EITHER SEPARATELY OR MIXED, AND IN THE METHOD OF SEPARATING THE RESPECTIVE METALS, TOGETHER WITH APPARATUS EMPLOYED THEREIN
Year: 1880

page_text: LETTERS PATENT to Farnham Maxwell Lyte, of the Scientific Club, Savile
Row, in the County of Middlesex, for an Invention of "IMPROVEMENTS IN
TREATING ORES AND MATERIALS CONTAINING ZINC, LEAD, SILVER, COPPER,
IRON, AND IN SOME CASES ANTIMONY OR BISMUTH, EITHER SEPARATELY OR
MIXED, AND IN THE METHOD OF SEPARATING THE RESPECTIVE METALS,
TOGETHER WITH APPARATUS EMPLOYED THEREIN."
PROVISIONAL SPECIFICATION left by the said Farnham Maxwell Lyte at
the Office of the Commissioners of Patents on the 10th March 1880.
"
FARNHAM MAXWELL LYTE, of the Scientific Club, Savile Row, in the County of
Middlesex.. IMPROVEMENTS IN TREATING ORES AND MATERIALS CONTAINING
ZINC, LEAD, SILVER, COPPER, IRON, AND IN SOME CASES ANTIMONY OR BISMUTH,
EITHER SEPARATELY OR MIXED, AND IN THE METHOD OF SEPARATING THE
RESPECTIVE METALS, TOGETHER WITH APPARATUS EMPLOYED THEREIN."
This Invention relates in part to improvements founded upon those described in
the Specifications of my former Letters Patent dated respectively the '15th
February 1877, No. 633; the 23rd July 1877, No. 2807; and 22nd January 1879,
No. 269.
The aim and intention of this Specification is to describe a general and practical
method of working in part founded on the Inventions the subject of my said former
Patents, and intended to present in a practical consolidated form, a full and com-
plete system of treating the ores and metals referred to in the Specifications of my
said Patents, involving therein certain improvements intended to be specially
claimed and described.
It is well known that in many mining districts large quantities of mixed ores
occur, such, for instance, as blende or calamine mixed with argentiferous galena,
blende, and copper pyrites with or without galena, galena mixed with antimonial
ores, &c., and that in many cases the several constituents of such mixed minerals
are so intimately blended and mixed up, as either to entirely baffle every attempt
hitherto made on any practical scale to effect their separation by mechanical means,
or to render such separation only practicable with ruinous expenditure of labor, and
waste of the valuable materials of which the ores are composed.

page_text: The present Specification is intended to describe a general process and arrange-
ment of apparatus for separating the above named metals from such ores by
chemical means, employing for this purpose certain cheap reagents, such as the
waste hydrochloric acid from chemical works, brine, i.e., a very strong or a saturated
solution of sodium chloride, chalk, slaked lime, and common spelter, and thus to
obtain the metals either in the metallic state separated from one another, or in
some available commercial forms as marketable products.
Before proceeding to a description of my improved process, I will commence by
briefly summarising the principal actions on which it is based. Let us take for
example a mixed ore of blende with argentiferous galena and copper pyrites. Such
an ore is the so called bluestone of the Parys mountain and Mona mines of
Anglesea, in North Wales. By calcination of this ore most of its sulphur is driven
off, but part is oxidised into sulphuric acid, which remains in part combine with
the metallic oxides produced.
(1.) When the calcined ore is treated for a proper length of time with hot or
boiling hydrochloric acid of about 15 to 17% HCl in proper (not too large)
quantity, the zinc and the copper can be for the most part dissolved, and if this
solution be decanted off most of the lead and nearly every trace of silver remains
behind insoluble. (2.) On adding another like or nearly like quantity of hydro-
chloric acid, the lead is completely chloridised and is largely dissolved by this second
acid as well as much of the silver, and some of the sesqui-oxide of iron always
present in such ores after calcination is taken up as sesqui-chloride. This sesqui-
chloride of iron materially assists in bringing about the chlorination of the lead and
silver.
the whole
According then to the quantities of lead and silver present in the ore,
or part of these metals will have been dissolved, while portions of these may and
generally do still remain with the gangue as chlorides. (3.) If again this solution
of the chlorides of lead and silver in hydrochloric acid be decanted into another
vessel containing another charge of calcined ore, it will take up more zinc and
copper, and becoming more or less neutralised will allow much of the iron to
separate as sesqui-oxide, and together with it most of the lead and silver will again
separate and fall down, and the clear liquor being drawn off these will again
remain with the gangue.
Thus, in the first vessel where the ore was attacked, which for clearness we will
call A, we have a gangue with more or less lead and silver as chlorides; this said
gangue being still wet with some of the acid liquor containing sesqui-chloride of
iron, while the ore in the second vessel, which we will call B, has lost its zinc and
copper, but has got added to it some of the lead and silver withdrawn from A.
This general principle has been already set forth in the Specification of my Patent
dated 22nd January 1879, No. 269. Thus, it is evident that by proper manage-
ment, we can with the application of a fresh charge of acid chloridise all the lead
and silver in B, and by decanting once more onto a fresh charge of ore placed in A,
we can again abstract nearly all the lead and silver this acid has taken up, and
so on ad infinitum, always obtaining as residues the decanted (more or less
neutralised) liquors on the one hand, rich in zinc and copper, but poor in lead or
silver, and on the other hand gangue wet with acid, and containing the lead and
silver completely chloridised. Were these liquors decanted off quite neutral, they
would carry over in actual solution but insignificant traces only of lead or silver if
any. In practice however it is not convenient to obtain them so. Some traces
then of these metals are therefore still carried over, but as the liquors cool the
semi-neutralised acid, zinc, and cupreous liquors which have been so decanted off,
when allowed to stand and cool, deposit nearly every trace of the lead and silver
chlorides they may have carried over, whether that which may have been carried
over in suspension, or the small quantities which may have been taken into actual
solution.
The actual quantity of hydrochloric acid to be employed will of course depend in
each case on the composition of the ore to be treated. In treating the Parys

page_text: mountain and Mona bluestone, I employ about 6 or 7 of acid of 15% HCl to
one of calcined ore, but the quantity is easily adjustable for each kind of ore by an
experiment in the laboratory on a small scale, or may be calculated on an analysis
of the ore.
We thus see how the zinc and for the most part the copper may be
separated from the lead and the silver. (4.) If a quantity of strong brine (say
10 gallons of brine to every 4 pounds of lead the charge of ore may have contained)
be now heated to boiling, and flushed bot onto the gangue with the lead and silver
and boiled up with it, the lead and silver are entirely taken into solution, and this
brine being run off as hot as possible into a clean vessel and cooled, will deposit
most of its lead as lead chloride, but none of its silver, the latter metal being
retained entirely in solution, provided it be not present in larger proportion than
about /oth part of the lead, or providing there be at least about 10 gallons of brine
to every 18 oz. of metallic silver the ore contained. The silver does not usually
occur in such quantity as this, but if it does the quantity of brine must of course
be increased and apportioned to it, if all the silver is intended to be taken up and
retained in solution on cooling.
I have ascertained that lead chloride is soluble in boiling saturated solution of
sodium chloride (brine) to the extent of about 533 parts (= 40 parts of metallic
lead) to 1000 boiling brine, whereas on cooling down to ordinary temperatures
most of the chloride of lead crystallises out until no more than about 10-8 of lead
chloride (8 of metallic lead) to 1000 of brine remains in solution. Silver is
soluble in the same liquid to the extent of about 0.75 parts of silver under the form
of [silver chloride to 1000 of brine at 10° to 12° C., about 0.90 of silver to
1000 of brine at 25° to 26° C., and about double that quantity at a boiling tem-
perature. The presence of lead chloride in the brine seems rather to increase this
rate of solubility of silver as silver chloride. The solution of silver chloride in
brine appears to be peculiarly liable to what is termed supersaturation, so much so
that it will often be found that brine saturated hot with silver chloride will remain
clear on cooling until some determining cause, such as the addition of an atom of
solid silver chloride, intervenes, when immediately the whole liquid will turn milky
from the separation of silver chloride. It thus becomes evident that when lead
and silver chlorides are together present they may be taken up, and if care be
taken to have brine enough present all the silver may be retained in solution on
cooling, while most of the lead becomes deposited as lead chloride. These reactions
of brine with the chlorides of lead and silver have already been set forth in the
Specification of my Patent of January 22nd, 1879, No. 269.
(5) If the brine, containing as it does after the above treatment yellow sesqui-
chloride of iron, be now treated in the cold state with chalk the iron, according to
the well known reaction, separates out as sesqui-oxide or basic sesqui-carbonate;
but, which should be specially borne in mind, the whole of the lead and silver are
retained in solution.
(Note.) In thus separating the iron from the lead and silver care must be taken
to operate as above stated on cool solutions. If the chalk be added to a hot or
boiling solution the whole or part of the silver may get precipitated with the iron.
This would appear to depend on the fact that the brine as it comes off from the ore
always contains a trace of proto-chloride of iron, which in a boiling and neutral
-solution reduces and precipitates the silver, but leaves it unaffected in the cold or
in an acid solution. This is further proved by the fact that if a solution of
bleaching powder or other suitable oxidising agent be added to the brine, together
with the chalk in sufficient quantity to perchloridise all the iron present, the brine
may then be treated hot, or even boiled with chalk, without throwing down
the silver.
(6) If the decanted or filtered liquor be separated from the iron sesqui-oxide, and
a bit of spelter be immersed in it, the lead chloride still remaining and the silver
chloride are reduced together, with formation of spongy lead and silver on the one
hand, and zinc chloride, which passes into solution, on the other. It suffices,
however, and is more convenient in practice, to only precipitate part of the lead

page_text: from the brine, and by leaving this light spongy lead to float about and agitating
the brine the lead gradually picks up all the silver from the brine and becomes
very rich in this latter metal, and by flowing successive charges of argentiferous
brine into a tub properly disposed for the purpose, with bits of spongy lead floating
about in it, the silver may be picked up from each such successive charge and the
brine thus deprived of its silver, and then, as it contains but a fraction of the lead
it had taken from the last charge of ore, it may be pumped up and treated and
used afresh, and so may be used over and over again to take more lead and silver
out of successive charges of ore, depositing chloride of lead in one tub, iron in
another, and all the silver with but a little lead in a third, and so by mere reheating
the same lot of brine becomes repeatedly regenerated in its solvent powers, and so
on ad infinitum.
I specially specify in the Specification of my 1879 Patent, above mentioned, the
employment of lead as being the most suitable and convenient in these circum-
stances, and offering special facilities for the subsequent separation and refining of
the silver, and as being for this reason far superior to iron, copper, or any of the
metals, the employment of which may have been proposed for collecting silver from
its solutions. The fact of the silver remaining in the brine, together with what
lead is still retained in solution after cooling, facilitates this mode of recovery, and
at the same time facilitates the utilisation of the same brine over and over again as
a carrier and depositor of the lead on the one hand and of silver on the other, and,
as shown above, by so graduating the quantity of the brine as to make it sufficient
to retain the whole of the silver in solution, this metal may be hrown down com-
pletely and the brine kept free from silver, while the usually employed processes of
desilverising, or rather what should be called concentrating the silver in the lead
previous to cupellation, may be done away with, for the silver is thus at once
obtainable in a sufficiently concentrated form for immediate cupellation.
Having thus described the various reactions on which my improved system of
treating ores and metallic substances is based, I now proceed to a description of its
practical application, illustrating my text by reference to a convenient form of
apparatus.
This apparatus though capable of variations and modifications of form will better
serve to set forth the essential principles of my process. It comprises two attacking
tubs, which I will designate A and B, as before; they are conical, and are made
of the best pitch pine (or other suitable material), are 3 to 4 inches thick, and
about 5 feet diameter at the bottom, 4 feet 8 inches or 4 feet 9 inches at the top,
and 4 feet deep. In this description sets of two attacking tubs are described, but
sets of 3 may be used, the only object of using 3 in a set, however, being with a
view to obtain better neutralisation. These tubs are arranged on a platform about
8 feet above the ground, and stand on small separate movable platforms able to
be raised at pleasure by the hydraulic lift running on rails beneath them. This
lift is able to be run from end to end below the platform, and its use is to be able
rapidly to decant the liquors contained in either of the tubs into any other of its
set. Where only 2 tubs form a set only one lift and one set of rails will be required,
with 3 tubs, 2 lifts, and 2 sets of rails. Above these tubs and on a higher level,
say, 6 or 8 inches higher than the upper edges of the attacking tubs A, B, or, say,
5 feet 2 inches above the platform, is placed the hot brine tub. In this the brine
is heated to boiling when required, and it may be heated either by blind steam
through a copper or lead worm, or by a bottom of copper with a steam chamber
beneath.
The acid spout is for conveying acid to the tubs, and this and the steam pipes
require no particular explanation as they will be easily understood.
The steam should be properly trapped so as to carry off condensed water, and the
tubs are to be boiled when requisite by naked steam blown into them through a
copper or lead pipe, coupled onto the main by a stout indiarubber hose. This hose
should be of such size and length as to enable it to be drawn tightly over the lead
or copper pipe from end to end so as to cover it completely, and protect it from the

page_text: action of both acid and brine. No metal, or, at any rate, none of the baser metals,
such as lead, copper, or iron, should ever be allowed to come in contact with the
liquors in the attacking tubs. Below the platform on each side of it are a series
of cisterns in which the liquors are received, i.e., on one side are cisterns Nos. 1, 2, 3,
&c.. for receiving and treating the acid zinc liquors, and on the other are cisterns
Nos. 1, 2, 3, &c., for receiving and treating the brine. Their positions will easily
be understood.
The tubs in which the silver is extracted from the brine, hereafter referred to as
the desilverising tubs, should be covered tubs for protection from all dirt, provided
with a proper filter bed over or communicating with them, onto which the brine
has to be pumped or led by a spout from the brine neutralising tub No. 3, or it
may be passed through a wooden filter press provided with ebonite or non-metallic
pipes and adjuncts, and after being desilverised this brine may be again pumped
into another main reservoir, on a higher level than the hot brine tub, ready to be
run into the latter, as may be required for heating. Each of the attacking tubs
is furnished with a set of 3 or 4 wooden plugs with holes through them, onto which
are lashed indiarubber hoses. These plugs are placed at successive levels one above
the other in the lower parts of each of the tubs, and the ends of the hoses when
not in use may be thrown over the upper edges of the tubs to which they belong.
In this position of course they will not run. By successively lowering each hose
of any one tub in turn, beginning with the upper one, the liquors may be drawn
From the hot brine tub a
off clear down to the gangue after each attack.
similarly arranged hose leading from its lower part is employed to flush the boiling
brine into each tub in turn after the acid attack has been completed. A tub may
also be kept in any convenient position in which fresh brine may be made, or an
excess of salt may be kept always supplied into the upper reservoir of desilverised
brine so as to keep the brine always up to strength.
I now proceed to describe the operation of my process, taking, for example, the
treatment of some of the bluestone above mentioned. The ore is to be calcined,
powdered, and sifted to a mesh of 60 to the inch. About 600 lbs. of this powdered
calcined ore are placed in the attacking tub A, which is to be filled to within about
a foot of its upper edge with the dilute hydro-chloric acid above mentioned; the
indiarubber jacketted steam pipe is to be immersed in it, and steam blown in till
the acid boils. The liquor is to be boiled and well stirred for an hour or an hour
and a half. It is now allowed to settle for an hour, and the tub A being raised by
the hydraulic lift the liquor is drawn over into B, in which has been placed another
600 lbs. of powdered calcined ore. The same operation of boiling and settling is
repeated in B, and the clear liquor is then drawn off down to the precipitate, and
carried into the acid zinc liquor cistern No. 1. Meanwhile another charge of acid
of like quantity and strength is boiled in tub A, and decanted into B as before, and
again boiled on the precipitate in B. Again, a tub full of brine having been
brought to boil in the hot brine tub, this boiling brine is flushed into A by means
of the hose above described, and is boiled again by naked steam through the
jacketted steam pipe. Be it here observed that when the steam is blown into the
; acid which is cold this acid increases more or less in bulk by addition of condensed
water; but, on the contrary, when blown into the brine, which is already as near
boiling as possible, the-brine-boils at once, and takes up but insignificant traces of
water from the steam. The brine is boiled in A for half to three quarters of an
hour, being well stirred all the time, and it is now covered and the brine allowed
to settle for 2 hours or so, when it should have become fairly clear, and this brine
is to be drawn off into either of the brine tubs No. 1 or No. 2 for depositing lead
chloride.
If requisite, i.e., if the gangue still retains lead or silver, another lot of boiling
brine may be run into A, boiled, settled, and again run off, when nothing but
This gangue is
5 gangue entirely deprived of lead and silver should remain in A
removed from A and may be placed on a drainer so arranged that its drippings

page_text: may become added to "the brine in brine tub No. 1 or No. 2, and none be lost.
A now receives a fresh charge of 600 lbs. of ore, and the liquid in B, which, as
above stated, was the second acid from A, is also drawn over into acid zinc liquor
tub No. 1, and a fresh charge of acid poured into B, boiled, settled, and decanted
into A. B is now treated with brine as A was. Thus seriatim each tub of the two
in its turn becomes the first in the series, and no liquor is drawn off into acid zinc
liquor tub No. 1 or No. 2 till it has circulated over two lots of ore, of which the
last should be fresh ore, while before removal each gangue is to be treated with
brine as just described. The brine then, as is understood, becomes charged with
lead and silver, while the acid takes up the zinc and the copper, and carries over
but little lead or silver, and nearly every trace even of these last named metals, as
above stated, falls out of the said zinc liquor on cooling. When the acid zinc liquor
tub No. 1 or No. 2 is emptied this precipitate has only to be collected and added
to the ore in one of the attacking tubs when a charge of brine is being poured on,
and so even this lead and silver ultimately passes into the brine.
In practice it will be found that 4 attacking tubs, i.e., two pairs will feed one
acid zinc cistern and one brine cistern of the sizes given in 12 hours, and as these
will take 24 hours to cool and deposit the lead chloride, each set of 4 tubs has 2
acid zinc and copper cisterns No. 1 and No. 2, and 2 others, brine cisterns No. 1
and No. 2, so that Nos. 2 may serve while Nos. 1 are cooling, and so on. As the
brine in the brine tubs No. 1 or No. 2 cools, it deposits chloride of lead as above
explained, and is then to be drawn off into the brine neutralising tub No. 3,
through a rubber hose or shoot. In this tub No. 3 it is to be neutralised by chalk
when the iron sesqui-oxide becomes insoluble and subsides. The clear brine still
containing its lead and silver is drawn off into the desilvering tub, and the iron
sesqui-oxide thrown on a drainer or passed through a wooden filter press with
ebonite pipes, and all the brine which thus drains off is added to that in one of the
desilverising tubs. Thus, as will be seen, we make the brine leave most of its lead
as lead chloride in brine tub No. 1 or No. 2, its iron in the brine neutralising tub
No. 3, while it finally carries all its silver with it and still a little lead into the
desilverising tub.
In the brine contained in the desilverising tub I suspend a few lumps of spelter.
This speedily produces the well known metallic lead precipitate, which from time
to time may be knocked or shaken off from the spelter, and when enough of this
spongy lead has become detached and floats in the brine the spelter may be with-
drawn. I thus produce a fractional precipitation of the lead. On agitating this
brine from time to time with a wooden rake this lead extracts all the silver from
the brine. In some cases I use powdered zinc instead of lumps of spelter for
effecting the desilverising operation. I always take care to have an excess of this
lead in the desilverising tub, and when I observe that the brine desilverises too
slowly, I apply the spelter again as before for a few hours. Of course, accordingly
as more or less of the spongy lead is precipitated, so the silver lead obtained will
be less or more argentiferous. It will be found that by proper management the
lead is obtained fit to be cupelled at once, and far richer than that obtained by any
other process I know of.
In order to get the spongy lead as light and finely divided as possible, as well as
to get the brine clear and bright before the spelter is dipped into it, about half %
of the solution of 15° H Cl, such as is used in the attack may be added. This
causes a generation of small bubbles of hydrogen on the zinc, which puff up the
reduced lead, and render it light and spongy. Some lead chloride is found mixed
with the argentiferous lead precipitate in the desilverising tub, and this may either
be reduced by spelter before fusion, or extracted by hot water or brine.
The lead chloride deposited in the brine cistern No. 1 or No. 2, may be purified
by recrystallization, and is useful in the arts, and readily saleable.
Finally, we come to the treatment of the cupriferous acid zinc liquor. When cool 5
and settled it is drawn off into the zinc liquor neutralising cistern No. 3, and there

page_text: neutralised with chalk and allowed to settle, the clear portion decanted, and the
residual liquor there extracted by a filter press and added to the rest. If it be
wished to separate the copper, a wooden filter press should be used, and iron pipes
avoided. The copper may be thrown down by spelter, iron, or any other metal, or
any known mode of precipitation may be used, and the chloride of zinc should be
heated to boiling, and decomposed with precipitation of oxide of zinc by the slightest
possible excess of cream of lime. The only special precaution is to precipitate the
zine in a boiling solution, as the oxide obtained is thus produced denser and purer
in all respects: This part of the process has already been sufficiently described in
my Patent of 15th February 1877, No. 633.
One word as to the separation of antimony or bismuth from lead ores, or such
ores as are generally rich in silver, but are impossible to treat by fusion on account
of the antimony they contain. They should be calcined, or may even frequently
be treated raw if well pulverised with hydrochloric acid as above. The acid may
thus be made to carry off the antimony and leave lead and silver chlorides, which
are extracted by brine and separated as above described.
This process is of course likewise applicable to the extraction of either lead or
silver from the flue stuff of lead works, lead sulphate, and many other waste
products of chemical manufacture containing these metals.
1

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
10th September 1880.
FARNHAM MAXWELL LYTE, of the Scientific Club, Savile Row, in the County of
Middlesex. "IMPROVEMENTS IN TREATING ORES AND MATERIALS CONTAINING
ZINC, LEAD, SILVER, COPPER, IRON, AND IN SOME CASES ANTIMONY OR BISMUTH,
EITHER SEPARATELY OR MIXED, AND IN THE METHOD OF SEPARATING THE
RESPECTIVE METALS, TOGETHER WITH APPARATUS EMPLOYED THEREIN."
This Invention consists in part of improvements-upon the processes described in
the Specification of Patents granted to me numbered and dated respectively as
follows: No. 633, 1877, dated 15th February; No. 2807, 1877, dated 23rd July;
and No. 269, 1879, dated 22nd January.
It is commonly known among persons engaged in mining operations that
certain mixed ores are hardly if at all saleable, and all over the world immense
masses of such minerals are consequently either left altogether unworked, or if in
order to get at the purer portions of the lodes they are extracted, they are thrown
into the waste heaps, and are thus lost, encumbering mines with useless deposits as
well as adding seriously to the cost of working.
Among mixtures of most frequent occurrence, and of the greatest value as regards
their several constituents, may be cited galena (argentiferous sulphide of lead) often
found mixed with blende (sulphide of zinc), either carbonate of lead or galena
mixed with calamine (carbonate of zinc), or with the silicate of that metal, copper
or iron pyrites with blende or galena; all or any of these minerals also constantly
occur mixed with heavy spar (sulphate of baryta). The respective densities of the
components of such mixtures are all so similar as to render their separation by
dressing a most delicate, costly, and wasteful operation, and innumerable deposits
of minerals occur in metalliferous districts where the constituents are so intimately
blended as to defy every attempt at mechanical separation.
The processes now about to be described are for the separation of the metals,
lead, zinc, silver, copper, and iron, in these ores by a peculiar wet method, wherein
the various metals are separated by chemical treatment, and have in view the
employment of the cheapest possible reagents, such as brine, hydrochloric acid,
old scrap zinc, or hard spelter, chalk, and quicklime, thus rendering it possible to
utilise economically on a large scale otherwise relatively valueless ores often
hitherto treated as refuse, and to present them in marketable forms either directly
applicable in the arts, or treatable by the ordinary modes of smelting for the
production of the pure metals.
Before proceeding to a description of this process it will be well for clearness
sake to commence by briefly summarising the principal reactions on which it is
based. Let us take, for example, a mixed ore containing blende with argentiferous
galena and copper pyrites. Such is the so called bluestone of the Parry's mountain
and Mona mines of Anglesea, in North Wales. By calcining this ore most of its
sulphur is burnt off, but part is oxidised into sulphuric acid, variable quantities of
which remain combined with the metallic oxides produced. The gases resulting
from this calcination strongly charged with sulphurous acid may be utilised for the
manufacture of sulphuric acid. There generally remains in the calcined ores from
3 to 5 per cent. of sulphur in one form or another, but this does not interfere with
the treatment of the ore. When this calcined ore is first finely pulverised and then
treated for a certain length of time with hot or boiling hydrochloric acid of about
15 to 17 per cent. HCI in proper quantity, i.e., the quantity requisite to bring
into solution the zinc and other more soluble bases, the zinc and the copper can be
for the most part dissolved, and if this solution be now decanted off and cooled
most of the lead and silver remain insoluble, either with the gangue in the attacking

page_text: tub, or separate out of the decanted liquor as it cools. (For the most perfect
working of the process the acid should be used in such quantity as to leave an
excess of about 5 or 6 per cent. of free H Cl still in solution together with the
chlorides produced, but some latitude is allowable in this respect). On adding
another like quantity of hydrochloric acid, the lead as well as that part of the
silver which may have before escaped attack, becomes completely chloridised and
largely dissolved by this second acid, while more or less of the sesqui-oxide of iron,
always present in such ores after calcination, is taken into solution as sesqui-
chloride. This sesqui-chloride of iron seems materially to assist in completing the
chlorination of the lead and silver. According then to the quantities of lead and
silver present in the ore, the whole or part of these metals will have been dissolved
by this second acid, but portions of these may and generally do remain mixed with
the gangue as chlorides. If again this solution of the chlorides of lead and silver
in hydrochloric acid resulting from this second attack be decanted into another
vessel containing a fresh charge of calcined ore, it will take up more zinc and
copper, and becoming partially neutralised most of the lead and silver will again
separate and fall down as the liquor cools, so that the clear liquid may be drawn
off nearly free from lead or silver. This system of treatment has already been set
forth in my Patent for a continuous methodical and alternate treatment as applied
to these ores dated 22nd January 1879, No. 269.
These operations being completed, the first vessel where the ore was attacked,
which for clearness we will call A, will contain a gangue together with more or less
lead and silver chlorides, this said gangue being still wet with some of the acid
liquor of the second attack containing sesqui-chloride of iron. The ore, on the
other hand, in the second attacking vessel, which we will call B, will have lost
most of its zinc and copper, but will have got added to it some of the lead and
silver drawn over from A by the second acid. It is now evident that by
boiling the partially saturated acid with the fresh ore in the second vessel B,
allowing it to settle, and decanting the liquor off, we can with the application of a
fresh charge of acid chloridise all the lead and silver in the new batch of ore in B,
and by decanting B once more onto a fresh charge of ore placed in A we can again
cause nearly all the lead and silver this acid had taken up to reprecipitate on
cooling, and so on ad infinitum, always obtaining as residues on the one hand the
decanted (partially neutralised and cooled) liquors rich in zinc or copper, but poor
in lead or silver, and on the other hand gangues wet with acid and containing the
lead and silver completely chloridised. Were these liquors decanted off quite
neutral they would retain and carry over in actual solution but insignificant traces
of lead or silver, and nearly the whole of these metals would remain with the
gangue as chlorides when settled. In practice however where speed is desirable it
is not convenient to obtain them so since they have to be decanted while still bot.
Some traces of these metals are therefore still carried over in the hot decanted
liquors, but these weakly acid zincous and cupreous liquors when allowed to stand
and cool deposit nearly every trace of the lead and silver chlorides they may have
carried over, whether that which may have been carried over in suspension, or that
which may have been taken into actual solution. The object of this mode of
treatment is not to obtain precisely speaking, neutral, but rather weakly acid and
fairly dilute solutions of the chlorides of zinc or copper. Lead chloride is less
soluble jin cold weak HCl than in either cold strong H Cl or pure cold water, and
silver chloride, like it, appears to be far less soluble in cold weak than in cold
O strong solutions of HCl or of zinc chloride,
The acid zinc liquor derived from the attacks of the several batches of ore by the
hydrochloric acid contains, as well as zinc and copper chlorides, the chlorides of any
other soluble bases the ore may have contained, usually iron, alumina, lime, and
often some soluble silica. If this liquor be simply neutralised with chalk, i.e., if
5 chalk be added and stirred up with the liquor till a further addition ceases to cause
effervescence, the iron and alumina it contains are for the most part precipitated,
only that iron remaining in solution which the calcined ore may have contained as

page_text: protoxide or sulphide. If the liquor be now decanted through a filter this
precipitated iron, together with any excess of chalk which may have been added,
as well as the silica and alumina present, are retained while the liquor passes off
containing the copper and the zinc. If the work has been carefully conducted no
more than four grains of silver to each cubic foot of zinc liquor should remain in
solution, and even this silver, if it be considered worth while, may be collected by
some spongy lead reduced by means of spelter from a solution of chloride of lead in
brine. The copper and these traces of silver may also be conveniently extracted
by immersing bits of spelter or scrap zinc in the neutralised filtered solution; and
finally the zinc may be extracted as oxide by heating the solution to boiling, and
treating it, while boiling, with the least possible excess of lime in the form of
milk of lime.
The actual quantity of hydrochloric acid to be employed in the attack will of
course depend in each case on the composition of the ore to be treated. In treating
the Welsh bluestone already mentioned about 61/, or 7 of acid of 15%. H Cl to one
of calcined ore may be used, but the quantity is easily adjustable for each kind of
ore by an experiment in the laboratory on a small scale, or the quantity requisite
may be calculated on an analysis of the ore. We thus see how the zinc,
and for the most part the copper, as chloride may be separated and decanted off from
the lead and the silver chlorides, which are left insoluble in the cooled liquors or
with the gangue. If now a quantity of strong brine (say 10 gallons of brine to
every 4 pounds of lead the charge of ore may have contained) be now heated to
boiling and flushed hot onto the mixture of gangue with the lead and silver
chloride and boiled, those chlorides of lead and silver which separated from the
zinc solution on cooling being returned to the gangue, the lead and silver are
entirely taken into solution, and this brine being allowed to settle and run off as
hot as possible into a clean vessel and cooled, will deposit most of its lead as lead
chloride, but none of its silver, this latter metal being retained entirely in solution,
provided it be not present in larger proportion than about 1/50th part of the lead,
or providing there be at least about 10 gallons of brine to every 1.8 oz., of metallic
silver the ore contained. Silver rarely occurs in larger quantity than this, but if
it does the quantity of brine must of course be increased and apportioned to it, so
that all the silver may be taken up and retained in solution on cooling.
Strong solutions of any of the alkaline or alkalino-earthy chlorides may, as stated
in the Specifications of my former Patents, if desirable, be substituted for the brine,
and wherever the use of the latter is spoken of the practicability of this substitution
should be understood. In places where salt is too dear the calcium chloride
resulting, as will be seen hereafter, from the precipitation of the zinc oxide may
very well be employed, and is almost a better solvent, both for lead and silver
chlorides, than solution of sodium chloride is. Magnesium chloride serves equally
well.
Lead chloride is soluble in boiling saturated solution of sodium chloride (brine)
to the extent of about 53 3/4 parts (= 40 parts of metallic lead) to 1000 parts by
measure of boiling brine, whereas on cooling down to ordinary temperatures most
of it crystallises out until no more than about 10-8 of lead chloride (= 8 of metallic 4
lead) to 1000 of brine remains in solution. Silver is soluble in the same liquid to
the extent of about 1 of silver chloride (= 0.75 parts of metallic silver) to 1000 of
brine at from about 10° to 12° C. and about 1-2 of silver chloride to 1000 of brine at
from about 25° to 26° C., and about double that quantity at a boiling temperature.
The presence of lead chloride in the brine would appear not to diminish this rate of 5
solubility of silver as silver chloride. The solution of silver chloride in brine
appears to be peculiarly liable to that condition chemically termed super-saturation,
so much so that it will often be found that hot brine saturated with silver chloride,
will remain clear on cooling until some determining cause, such as the addition of
an atom of solid silver chloride, intervenes, when immediately the whole liquid 5
will turn milky from the separation of silver chloride. It thus becomes evident
that when lead and silver chlorides are present together they are dissolved, and if

page_text: care be taken to have brine enough present all the silver is retained in solution on
cooling, while most of the lead becomes deposited as lead chloride. If the cooled
brine still containing, as it generally does, some ferric chloride, be now decanted
from the precipitated lead chloride, and a strip of zinc be immersed in it, the lead
chloride still remaining in solution and the whole of the silver chloride are reduced,
together with formation of spongy lead and silver on the one hand, and zinc
chloride, which passes into solution, on the other. It suffices however, and is
more convenient in practice, to only precipitate part of the lead from the brine,
and by leaving this light spongy lead floating about, and agitating the brine with
it, this lead gradually picks up all the silver from the brine till it becomes very
argentiferous. Successive charges of argentiferous brine may be run into a tub
properly disposed for the purpose, with bits of spongy lead floating about in it,
and the silver picked up from each such successive charge, the brine being thus
desilverised. This brine then, as it now contains but a fraction of the lead it had
taken from the ore and no silver, may be pumped up, neutralized if necessary, re-
heated, and used afresh. Thus the same brine may be employed over and over
again to take more lead and silver out of successive charges of ore, depositing lead
chloride in one tub, and all the silver with but little lead in a third, while by mere
reheating the same lot of brine becomes repeatedly regenerated in its solvent
powers.
The above mentioned employment of spongy lead is by far the most suitable and
convenient in these circumstances, and offers special facilities for the subsequent
separation and refining of the silver, being for this reason far superior to iron,
copper, or any of the metals the employment of which may have been previously
proposed as a means of collecting silver from its solutions. The advantage of this
form of lead is principally in the fact of its presenting so large a precipitating
surface, but fine lead filings, fine hair-like wire of lead, or lead foil may be employed,
the necessary condition being the presentation of a large metallic precipitating
surface to the argentiferous solution. Pigs of lead, bars, or even coarse lead wire, are
almost useless, as they become nearly inert after a very short time of immersion.
The fact of the silver remaining in the brine, together with what lead is still
retained in solution after cooling, especially facilitates this mode of its recovery,
while it admits of the utilization of the same brine over and over again as a carrier
and depositor of the lead on the one hand, and of silver on the other, and, as shown
above, by so proportioning the quantity of brine as to make it sufficient to retain
the whole of the silver in solution, this metal can be entirely carried over into a
separate tub or vessel, where it may be thrown down completely, the brine being
thus freed from silver at each successive 'operation. The process of desilverising
usually employed, or rather what should be termed concentrating the silver in lead
previous to cupellation, may be dispensed with when this process is employed, for
the silver is thus at once obtainable with lead in a sufficiently concentrated form
for intermediate cupellation. Heating the brine during the desilverising materially
accelerates the operation, a tubful being thus able to be completely desilverised in a
few hours. As the brine often contains traces of copper gathered from the ore, it
is usually convenient to so apportion the lead thrown down as to have enough of
that metal present to ensure proper cupellation, and further, in order to avoid loss,
it is well not to obtain the silver in too concentrated a form; lead-with-2-to-4 per-
cent. of silver will be rich enough, the quantity of lead precipitated being of course
proportionate to the time of immersion of the spelter, the quantity of the spelter
employed, and the temperature of the brine.
Argentiferous precipitates are however easily obtainable with 28 or 30 per cent.
of silver from ores containing but a few ounces of silver per ton. Instead of spelter
zinc dust may be used for this precipitation; or instead of employing spongy lead at
all for the collection of the silver, the same end may be obtained by stirring into the
argentiferous brine some precipitated lead or copper sulphide. This will also gather
the silver from the brine, though not perhaps quite so efficaciously or as rapidly as
the spongy lead:

page_text: Having thus described the various reactions on which my improved system of
treating ores and metallic substances is based, I will now proceed to describe its
practical application, illustrating my text by reference to Drawings of a convenient
form of apparatus annexed hereto. This apparatus, though of course capable of
variations and modifications of form, will enable me to assist in setting forth the
essential principles of the process.
A and B are two attacking tubs; they are conical, as shown in the accompanying
plans, may be best made of good sound pitch pine wood creosoted with petroleum
or other suitable material capable of resisting acid, are 3 to 4 inches thick, and
about 7 feet diameter at the bottom, 6 feet 6 inches at the top, and 4 feet deep.
These dimensions are of course open to variation. In the accompanying plans sets
of two attacking tubs are figured, but sets of three or more may be used; the only
object of using three in a set is merely with a view to obtain better neutralization,
and this can be sufficiently obtained with a set of two tubs; the advantage of using
more tubs in a set is dubious. These tubs are arranged on a platform about, say,
8 feet above the ground, and stand on small separate movable platforms able to be
raised at pleasure, or lowered back into their places by the hydraulic lift running
on rails beneath. This lift can be run from end to end below the platform, and
its use is to be able rapidly to decant the liquors contained in either of the
tubs into the other next to it in any given set. The ram may, of course, be
equally well applied to lower any one of the tubs for the purpose of decantation
as to raise any one of them, the object being to have such an arrangement
as to be able to change the respective levels of any pair of the tubs at will,
and of course other mechanical contrivances for raising or lowering the tubs
may be adopted. Above these tubs and on a higher level, say, 6 or 8 inches higher
than the upper edges of the tubs A, B, or, say, 5 feet 2 inches above the platform,
is placed the hot brine tub D. In this the brine is heated to boiling when required,
and it may be heated either by blind steam through a copper or lead coil, as shown
in the plans, or by a bottom of copper with a steam chamber beneath. The acid
spout is for conveying acid to the tubs, and this and the steam pipes, which are also
figured, require no particular explanation. They will be easily understood by a
mere inspection of the diagrams. The steam should be properly trapped, as shown
in the diagrams, so as to carry off condensed water, and the tubs are to be boiled
when requisite by naked steam blown into them through an embedded indiarubber
hose, or indiarubber jacketted steam pipes, properly weighted at the end to prevent 3
the steam from blowing it out of the liquor. This hose should be of such size and
length as to enable it to descend to the bottom of each tub, and so embedded inside
and out as to cover and protect all metal it may contain from the action of both
the acid and the brine into which it has to be plunged. It is advisable that no
metal, or at any rate none of the baser metals, such as lead, copper, or iron, should 4
be allowed to come in contact with the liquors in the attacking tubs. Below the
platform on each side of it are a series of cisterns in which the liquors are received,
i.e., on one side are cisterns Z1, Z2, Z3, &c., for receiving and treating the acid zinc
liquors, and on the other are cisterns S1, S2, &c., for receiving and treating the brine.
Their positions will easily be understood by reference to the diagrams. The tubs 4
in which the silver is extracted from the brine are figured as C¹ and C². These
tubs should be covered for protection from all dirt, and may or may not be heated
by a serpentine or any other convenient method to accelerate the desilverisation.
The bottoms of these tubs may be bevelled for the more easy collection of the
argentiferous precipitate. Each attacking tub is furnished with a set of 3 or 4 wooden 5
plugs with longitudinal holes through them, onto which may be lashed indiarubber
hoses. These plugs placed at successive levels one above the other in the lower part
of each tub, serve the part of taps for decanting, and the ends of the hoses when
not in use may be thrown over the upper edges of the tubs to which they belong.
In this position of course the liquor will not run off. By successively lowering each 5
hose of any one tub in turn, beginning with the highest, the liquors may be drawn
off clear, down to the gangue after each attack. The reason why taps cannot be

page_text: employed is that they become rapidly clogged and stopped up by crystallised lead
chloride, whereas the hoses being flexible and the wooden nozzles being straight
they are easily kept clean. They are of rubber and wood respectively, as at this
part of the process the liquors should not be brought into contact with any base
metal if possible, for fear of precipitating silver. From the tub D one similarly
arranged hose leading from its lower part is employed to flush the boiling brine
into each tub, as may be required, after the last acid attack has been completed. A
tub may also be kept in any convenient position in which fresh brine may be
made, or otherwise an excess of salt may be kept always supplied in the reservoir
of desilverised brine so as to keep the brine always up to strength. The desilverised
brine reservoir may be of iron or wood lined out with lead and may be placed
underground, as in the plans, running the whole length of the plant with holes to
pump from and man holes for cleaning it out.
I will now proceed to describe the working of the process, taking always for
example the treatment of some of the bluestone above mentioned, and merely
remarking that this being a continuous alternate process I commence with the
description supposing the working to be already in operation.
The ore is to be calcined, powdered, and sifted to a mesh of, say, 60 to the inch.
Supposing the process to be already in operation, about half a ton of this powdered
calcined ore is placed in the attacking tub A while the partially saturated acid
liquor from the previous attack is decanted into it. The indiarubber jacketted or
embedded rubber steam hose is to be immersed in it, and steam blown in until the
acid boils. The liquor is to be boiled and well stirred for an hour or an hour and a
half. It is now allowed to settle, and the clear liquor is then drawn off down to
the precipitate and carried into one of the reservoirs Z¹ or Z³. A fresh quantity
of acid is then run in to within about a foot of the upper edge of the tub and
boiled. It is now allowed to settle for an hour or so, and the tub A being raised
by the hydraulic lift, the liquor is drawn over into B, half a ton of powdered
calcined ore being at the same time added, A being now ready for treatment with
brine. The same operation of boiling and settling is repeated in B, and the clear
liquor is then drawn off down to the precipitate and carried into one of the
reservoirs or Z2, and so on.
Meanwhile the tub D full of brine baving been brought to boil this boiling brine
is flushed into A by means of the hose above described, and is boiled again by
naked steam through the jacketted steam pipe. Be it here observed that when the
steam is blown into the acid which is cold this acid increases, more or less, in bulk
(say, about 1/th) by condensation of water, but on the contrary when blown into.
the brine, which is already as near boiling as possible, the brine boils at once, and
takes up but insignificant traces of water from the steam. The brine is boiled on
the ore in A for from 1/2 to 3/4 of an hour, being well stirred all the time. It is
well here to observe that the use of the tub D is to avoid having to heat the brine
by naked steam since dilution interferes with its solvent powers, but if only it be
concentrated from time to time in a separate vessel, or if it be always kept up to
strength by additions of fresh salt, the heating tub D may be dispensed with; also
if sufficiently strong solutions of the alkalino-earthy chlorides (chloride of calcium
or of magnesium, for instance) be employed in place of brine for dissolving the lead
and silver chlorides; such saline solutions may be heated with naked steam blown
direct into them, always observing the precaution of employing a non-metallic
steam pipe, as above described, to avoid precipitating silver. Solutions of the
alkalino-earthy metals do not require to be so near their points of saturation in
order to be able to take up considerable quantities of the chlorides of lead and
silver, and so the condensed water from the naked steam does not so much interfere
with their solvent powers. The tub A is now covered and allowed to settle for
2 hours or so, by which time the liquor should have become fairly clear, and is
then to be drawn off into one of the tubs S' or S2. If requisite, i.e., if the gangue
still retains notable quantities of lead or silver, another lot of boiling brine may
be run into A, boiled, settled, and again run off, when nothing but gangue entirely

page_text: deprived of lead and silver, or containing but mere traces of these metals, should
remain in A. This gangue is removed, and may be placed on a drainer so arranged
that its drippings become added to the brine in S¹ or S2 and none be lost. A now
receives a fresh charge of half a ton of ore, and the liquid in B, which was the
second acid from A, is also drawn over into Z and a fresh charge of acid poured
into B, boiled, settled, and decanted into A; B is now treated with brine as A was.
Thus, seriatim, each tub of each pair in its turn becomes the first in the series,
and no liquor is drawn off into Z or Z2 till it has circulated over two lots of ore,
of which the last should be fresh ore, while before removal each gangue is treated
with brine, as described. The brine it is understood becomes thus charged with
lead and silver while the acid takes up the zinc and the copper, and carries over
but little lead or silver, and even what is carried over of these last named metals
is deposited, as above stated, from the acid zinc liquor on cooling, so that when the
tub Z or Z, as the case may be, is emptied this precipitate has only to be collected
and added to the ore in one of the attacking tubs when a charge of brine is being
poured on or attacked separately with a charge of brine. So even this lead and
silver ultimately passes into the brine.
In practice it will be found that 4 attacking tubs, i.e., two pairs, will feed one
acid zinc cistern and one brine cistern of the sizes given in 10 hours, and as these
will take 24 hours to cool and deposit the lead chloride each set of 4 tubes has 2
cisterns for acid zinc and copper solutions Z, Z³, and two brine cisterns S¹ and S²,
so that Z2 and S² may serve while Z' and S' are cooling, and so on. As the brine
in tubs S¹ or S2 cools it deposits lead chloride as already explained, and the clear
liquid still containing some lead and all the silver is drawn off into one of the
desilverising tubs C' or C2, there to be deprived of its silver, as will now be shown.
In warm weather artificial cooling with cooled compressed air might be advan-
tageously employed for the brine to accelerate the deposition of the lead chloride.
The apparatus of Messrs. Giffard and Berger, of Paris, may be employed. Six No. 3
machines will cool the liquors from 20 tons of calcined ore per day. Thus, as will
be seen, I make the brine leave most of its lead as lead chloride in S' or S2, while
it carries all its silver with it, and but a little lead, about 0.8 per cent., into the
desilverising tub.
I may here remark that if solutions of calcium or magnesium chlorides be
employed they will retain when cold more lead in solution at a given temperature
than cold brine does for equal densities of the solutions, but then they also dissolve
more lead when hot, and their solvent powers for silver chloride at equal tempera-
tures and densities are also greater than that of brine, so that their use may be
'equally or even more advantageous.
In the brine contained in the desilverising tub are suspended a few lumps of
spelter. This speedily produces the well known metallic lead precipitate (the so
called lead tree of toy chemistry) which. from time to time, may be knocked or
shaken off from the spelter, and when enough of this spongy lead has formed and
become detached floating in the brine, the spelter may be withdrawn. Thus is
produced a fractional precipitation of the lead. On agitating this brine from time
to time with a wooden rake, this floating spongy lead extracts all the silver from
the brine. In some cases powdered zinc may be used instead of lumps of spelter
for effecting the desilverising operation, being simply sprinkled into the brine and
raked about, or the sulphides before mentioned may be employed. Care should
always be taken to have an excess of this spongy lead in the desilverising tub, and
when it is observed that the brine desilverises too slowly the spelter should be applied
again as before for a few hours. Of course, according, as more or less of this
spongy lead is precipitated, so the silver lead obtained will be less or more
argentiferous, but it will be found that by proper management the lead is easily
obtainable, rich in silver and fit to be cupelled at once, and far richer indeed than
that obtainable by any other known process. In practice the argentiferous
precipitate may be obtained with any required amount of silver from 1 to 25, or
even 30 per cent. The small quantity of acid (about 1 per cent.) the brine

page_text: contains generates bubbles of hydrogen, which puff up the lead and render it light,
spongy, and finely divided, thus causing it to float about and present a large
surface for the collection of the silver, and as the silver collects on it each bit of
lead becomes a sort of floating silver lead couple of great activity, floating about
and collecting the rest of the silver. Some lead chloride is found mixed with the
argentiferous lead precipitate in the desilverising tub, and this may either be
reduced by spelter before fusion, thus adding to the proportion of lead to silver, or
extracted by hot water or hot brine, leaving the argentiferous precipitate all the
richer.
The lead chloride in S¹ or $2 may be purified by recrystallisation, and is useful
in the manufacture of oxychloride of lead for paint.
The brine on leaving the desilverizing tub may be pumped up into the tub D or
stored in the desilverised brine tank, but from time to time, or preferably at each
operation, it may be defecated and deprived of any iron, alumina, or silica and acid
it may contain. (The acid it contains at this period will be derived from the acid
zinc liquor, still wetting the gangue when the brine is run on, and the acidulation
of the brine by this means will generally amount to about 1 per cent.).
For this purpose it may be run into the pan Ss. This pan may be of wood or
iron lined with lead, and should be placed at such a level that the brine from C¹
or C² may be run off by a tap or hose direct into it. In this pan the brine may be
treated with chalk added in powder and stirred into it. Very little chalk suffices
for the neutralisation, and as some sulphuric acid is generally taken up from the
ore by the brine, some insoluble sulphate of lime falls down, and together with it
iron, alumina, and silica. A little bleaching powder may be sprinkled with the
liquor which peroxides any iron present, and causes its more complete precipitation,
but this is at most only occasionally necessary. As soon as the brine is neutral,
the iron, alumina, &c., separate out, and the liquor may be passed through the filter
press, which is figured running on rails so as to be able to serve several tubs
successively, and the clear brine is run off into the desilverised brine reservoir
where it is stored for use. From this reservoir the brine is pumped as required
into the tub D to be heated and used over again.
Of course, as stated in my former Patents, this process can be equally well
employed on ores containing no zinc, and ou those from which the zinc has been
already extracted by any other process. It may also be well to observe, that if
advisable, the iron may be thrown down by chalk before the precipitation of the
silver. If however the liquid be heated under these circumstances, the silver is
liable to become precipitated; indeed, by this means the silver may be entirely
separated from either the brine or the zinc chloride, leaving the lead chloride still
in solution, and may be thus obtained in a precipitate together with all or part of
the iron sludge, and it may be extracted from this precipitate by acid and brine, as
before described.
The treatment of the acid zinc liquors for the extraction of zinc oxide has been
sufficiently described in my former Patents, more particularly the acid chlorination
Patent, dated February 15th, 1877, and is therefore unnecessary to be recapitulated
here.
Although both in the title of these Letters Patent, and in the Provisional
Specification left by me with my petition for the said Letters Patent, reference is
made to the separation of antimony and bismuth, I have found on further
experiment that the treatment of the said metals, antimony and bismuth, is not of
so much practical value as I thought at the time of making my application for the
said Letters Patent, and I therefore do not make any claim to any treatment of the
said metals, antimony and bismuth.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is to be performed or carried into
effect, I declare that what I desire to claim as the Invention to be secured to me by
the said in part recited Letters Patent is,―
1st. My improved system or process of treating mineral ores or metallic mixtures

page_text: by means of apparatus arranged and employed substantially in the manner and for
the purposes herein described.
2nd. The apparatus hereinbefore described and represented in the Drawings
hereunto annexed for lifting or lowering the attacking tubs, so as to be able at
will to change the respective levels of any pair, whether by lowering one or raising
the other, when carrying out my system of alternate decantation, and the use of the
said or similar apparatus, substantially in the manner and for the purposes herein
described.
3rd. The fractional separation of the bulk of the lead as lead chloride, by cooling
the brine or saline liquor; the silver still remaining in solution, and being extracted
in a separate tub or vessel by means of finely divided metallic or spongy lead, or by
zinc, or by certain metallic sulphides, substantially in the manner herein described.
4th. I claim the use, as and for the purposes herein described, of chalk or other
like precipitant.
In witness whereof, I, the said Farnham Maxwell Lyte, have hereunto set
my hand and seal, this Ninth day of September, in the year of our Lord
One thousand eight hundred and eighty.
Witness,
WM. CLARK,
53, Chancery Lane,
London,
Patent Agent.
F. MAXWELL LYTE. (L.S.)