Lead-zinc Ores.
Year: 1897

page_text: Date of Application, 16th Feb., 1897-Accepted, 15th May, 1897
Lead-zinc Ores.
A communication from SOLOMON GANELIN and JOHN BLOCK, of 623 Parrish
Street, Philadelphia, Pennsylvania, U.S.A., Chemists.
I, ALFRED JULIUS BOULT of 111 Hatton Garden in the County of Middlesex
Chartered Patent Agent do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This invention relates to improvements in the wet process of decomposing lead
and lead-zinc ores and of producing chlorides of lead, zinc and silver therefrom.
It is well known that lead, zinc and silver chlorides can be obtained by the action
of a concentrated solution of hydrochloric acid upon the ores with the application
of heat. However, prior to the present invention, this reaction was only practical
in the laboratory because it presents defects and difficulties which preclude its use
for manufacturing purposes on a large scale. Attempts were made chiefly with
the most common and abundant galena and native lead-zinc ores, mostly sulphides,
by treating finely pulverized ore with a great excess of heated concentrated
solution of hydrochloric acid. According to all hitherto suggested methods and
after the reaction had taken place, the acid mixture was diluted with water, and
boiled in order to dissolve the formed lead-chloride and thus separate it from the
undecomposed part and impurities, and the lead-chloride was recovered by cooling
the hot solution whereupon the greater part of the dissolved lead-chloride was
thrown down as a crystalline mass. These methods presented among others the
following disadvantageous features: They required the employment of a great
excess of a concentrated solution of hydrochloric acid, which, after the reaction,
was dilute and unfit for further use in the process. The acid mixture was treated
with hot water which became acidulated and being hot corroded the vessels.
Lead-chloride is very little soluble in water, even when hot and still less soluble
when the water is acidulated with hydrochloric acid, so that large quantities of hot
water were required wbich entailed the provision of large plants and great
expenditure of heat and labor. The hydrogen sulphide evolved in the reaction
was contaminated by hydrochloric acid gas due to the heating and was
rendered valueless for the production of sulphuric acid. A part of the hydrogen
sulphide was absorbed by the hot solution, so that the lead-chloride crystallized upon
cooling, was not pure, was of a grayish color, and was unfit for use in the production
of lead pigments. Only a part of the ore, about 50 per cent., could be decomposed
and converted into lead-chloride.
thus
The methods hitherto suggested for treating the so-called lead-zinc ores were
still less economically successful, because, according to these methods the zinc and
the lead contained in the ores were only partly decomposed and converted into
chlorides which were both extracted by the hot solution, so that the lead could not
be separated from the zinc neither in the decomposed nor in the undecomposed
parts.
The principal objects of this invention are to obviate and overcome the above-
mentioned defects and disadvantageous features, to completely decompose the lead-
sulphide in the lead ores without wasting great quantities of acid, to decompose the

page_text: ores without the necessary application of heat, to obtain pure hydrogen-sulphide
gas fit for use in the arts, to free the lead-chloride from impurities without the
employment of large plants and great expense for fuel and labor, and to obtain
the final product in a pure white crystalline mass fit for the production of lead
pigments.
This process is well adapted for treating lead-zinc ores.
present invention, all the lead and silver, as well as the whole or most of the zinc
According to the
contained in the ore are converted into chlorides, and the zinc when not entirely
decomposed in the reaction, remains quite free from lead compounds, and at the
same time the formed or resultant lead-chloride, as well as the formed or resultant
zinc-chloride are extracted and obtained each respectively free from the other.
The present invention is based on the following facts, discovered, it is believed,
for the first time. First, it has been found that the native lead compounds, such as
sulphide, carbonate, and the like, are completely decomposed in the cold by hydro-
chloric acid in the presence of a chloride of a base in solid form, particularly in
the presence of calcium chloride, magnesium chloride, ammonium chloride, or a
mixture thereof, and that such compounds are similarly decomposed even in the
cold in the presence of such a chloride in a concentrated solution, provided use is
made of hydrochloric-acid gas. The accomplishment of this in the cold, as
described, is believed to be novel, and to be due to the fact that the formed lead
chloride combines with the chloride of a base present, and forms a double chloride,
which accelerates the reaction, probably because the formed double salt, being of
light in contradistinction to compact consistency, is readily penetrated by hydro-
chloric acid, and does not constitute an obstacle, as does lead-chloride, to the further
decomposition of the ore. Second, it has been found that lead and lead-zinc ores
may be decomposed more readily by hydrochloric-acid gas when the pulverized ore
is moistened with water before being subjected to the action of the gas, and in this
case the presence of chloride of a base also accelerates the reaction due to the
formation of the double salt mentioned. This double decomposition, effected by
hydrochloric-acid gas, and without previous desulphurization and oxidation, is
believed to be novel and advantageous. It has been further found that this reaction
by means of gaseous hydrochloric acid may be also accelerated by mixing the
moistened ores with chemically inert bodies, such as coal, coke, punice, infusorial
earth, and the like. These bodies impart a loose consistency to the mass, and
prevent the formed lead-chloride from constituting an obstacle to the complete
decomposition of the ore by the hydrochloric acid. It has been further found that
the lead and silver present in many lead-zine ores can be decomposed in the manner
described and by means of gaseous hydrochloric acid without recourse to the above-
mentioned foreign bodies, when the ores in their natural state contain foreign
matter in sufficient quantity and of such nature as to render the mass loose and
accessible to the action of the gas. In such cases mere moistening of the pulverized
ore with water suffices for the attainment of the complete decomposition of the lead
and silver compounds by means of hydrochloric acid. Third, it has been found
that solutions of most of the chlorides while hot dissolve comparatively large
quantities of lead-chloride, which, upon cooling, is mostly thrown down as lead-
chloride, or as double chloride of lead, and the base of the chloride used, according
to the strength of the solution employed; and, fourth, it has been found that the
separation of lead-chlorides from zinc-chloride may be accomplished by taking
advantage of the property of zinc-chloride to greatly increase the insolubility of
lead-chloride, which permits of leaching out zine-chloride from the mixture, and
leaving almost the whole of the lead-chloride as a solid mass.
This invention may be carried into effect by means of a solution of hydrochloric
acid in the manner to be described and in this description it will be assumed that
galena is the ore of lead to be decomposed for the production of chloride of lead.
Ground or pulverized galena is mixed with about an equal part by weight of
ground or pulverized and solid chloride, such as calcium chloride, magnesium
chloride or the like, which is intended to produce a double salt with lead chloride.

page_text: The mixture is then subjected to the action of a solution of hydrochloric acid
which may be at first dilute and when exhausted drawn off. Subsequently the
mixture is treated with concentrated commercial hydrochloric acid of about
22 degrees Baume. A novel feature of this process is that it does not require the
application of heat. This step occupies about two days. During this time the
galena is decomposed, hydrogen sulphide is evolved and may be collected for use
in the arts and there is left a grayish white mass containing lead-chloride and the
greater part of the added chloride both chemically united as a double salt
or mixture of double salts. This reaction may be illustrated by the following
formula:
xPbSyMeCl, + zH₂O + 2 xHCI = xPbCl₂. MeCl. zH₂O + xH₂S.
in which x, y and z represent parts that vary according to the nature of the
chloride used and in which Me represents a metal of double valency, although the
valency of this metal is not important. The existence of a double salt or chemical
compound should be accepted for the following reasons: First, there is no other
explanation for the fact that without the application of heat and in the cold the
easy and complete decomposition of galena is effected; second, the mass above
referred to is not acted upon or discolored when dry by sulphuretted hydrogen;
and, third, it gives when stirred in water a curdy snow-white precipitate like
silver-chloride when stirred in water. A similar curdy-white precipitate of lead-
chloride is given when a double salt of lead-chloride and other chlorides well
known in chemical literature as having a definite composition is stirred in water.
The described process of working galena applies also to the treatment of lead-zinc
ore3. In this connection it may be remarked that the added chloride accelerates
the decomposition of the zinc-sulphide in the lead-zinc ores and for this purpose
ammonium-chloride is well suited. By the use of ammonium-chloride not only the
lead compounds but also the zinc-sulphide can be completely decomposed, and
attention is called to the fact that, in the presence of ammonium-chloride, most of
the zinc-chloride is left in an insoluble state probably as a double salt with
ammonium-chloride, and only a part of it goes into the acid solution. When this.
solution is drawn off, zinc and silver can be recovered from it by well known
chemical or electrolytic processes. In cases where the ore is decomposed by
means of a solution of hydrochloric acid, the solution is drawn off and the mass is
dried in order to free it from adhering acid, hydrogen sulphide and hydrochloric
acid, so that pure lead-chloride of desirable color may be recovered from it as will
be hereinafter described.
In practicing the present invention by means of hydrochloric-acid gas pulverized
galena is first mixed with a chloride containing water. Excellent results have been
obtained by mixing equal parts by weight of pulverized galena with pulverized calcium,
ammonium or magnesium-chloride or a mixture of the same, each of these containing a
certain amount of water; for example, if calcium chloride is used, the quantity of water
contained in it should be in the proportion of from two to four molecules of water
for each molecule of calcium-chloride taken. In such case the reaction is very
complete and rapid, otherwise the reaction takes place slowly and incompletely and
the ore is decomposed with difficulty. If magnesium chloride is used the amount
of water contained in it should be in the neighbourhood of from six to seven
molecules of water for each molecule of magnesium chloride. The process is
carried out by passing hydrochloric acid gas through the mass in the cold. It
may be remarked that the same results are obtained wben instead of mixing the
ore with a chloride of a base in solid form the ore is placed in a concentrated
solution of a chloride and hydrochloric-acid gas passed through the solution,
though in practice it is found to be more convenient to work with chlorides in
solid form. For this purpose the mixture of the pulverized ore and the pulverized
chloride is placed in suitable apparatus such as cylinders, chambers, etc., through
which a current of hydrochloric-acid gas is passing. As additional evidence of
the existence of a double salt it may be stated that the mixture absorbs
hydrochloric-acid gas so eagerly and completely that at a distance of an inch

page_text: from the place where the ore is completely decomposed and turned white, the
mixture appears entirely black and not acted upon at all by the hydrochloric-
acid gas.
The easiness and completeness with which the above-described reaction takes
place is attributed not so much to the chemical reaction which results in the
formation of a double salt, as to the physical structure of the formed double salt,
which is comparatively light and porous, and thus permits hydrochloric-acid gas to
readily penetrate the whole mass. The reaction PbS + 2 HCl = PbCl, + H,S, is
an exothermic one, and should, therefore take place readily, and continue to
completion, but this never occurs, and the reason generally given is that the formed
lead-chloride covers the undecomposed particles of the ore, which are therefore cut
off from any further supply of hydrochloric acid. In the present invention this is
remedied by the formed porous double salt. Moreover, it is found that when the
reaction takes place in the presence of calcium-chloride, less heat is liberated than
when hydrochloric acid acts upon galena alone. This appears to indicate that the
formation of a double salt tends rather to absorb heat and hinder the reaction than
to facilitate or help it. In view of these facts it would appear that the formed
double salt facilitates the reaction principally in so far as its structure is porous,
and consequently readily permeable by the acid. Moreover, chemically indifferent
or porous bodies, as coal, pumice-stone, and the like, when mixed with the ore,
markedly facilitate the conversion of native lead-sulphide into lead-chloride.
Accordingly, use may be made of such chemically indifferent and porous bodies for
the complete decomposition of ores by mixing them in substantially equal parts by
weight with the ore, moistening the mass with water, and subjecting it to the action
of hydrochloric-acid gas for a considerable length of time, approximately two or
three days. Native lead ore when finely ground is a heavy, compact mass, not
readily penetrated by hydrochloric-acid gas, however an admixture of the
chemically inert substance imparts to it a loose and porous consistency which
enables the hydrochloric-acid gas to reach every part of the ore and act upon it.
Moreover, the particles of chemically inert matter prevent the formed lead-chloride
from enveloping undecomposed particles of the ore, which, of course, facilitates
the complete conversion. Moreover, the added chemically inert substance is
capable of absorbing comparatively large quantities of water, and being in intimate
contact with the ore, facilitates the reaction; for example, galena alone cannot
absorb more than 6 per cent. of its weight of water, but if galena is mixed with
25 per cent. of charcoal, for example, the mixture is capable of absorbing water to
the extent of 22 per cent. of the weight of the ore taken, and still remain very
porous. The presence of water necessary when a chemically indifferent body as
well as when a chloride of a base is used, and in practice hydrochloric-acid gas
generated from salt with not too concentrated sulphuric acid is often employed for
the purpose of adding more water to the mixture while the reaction goes on. The
foregoing description of the decomposition of galena by meaiis of hydrochloric-acid
gas applies to other lead compounds capable of decomposition by hydrochloric acid.
Lead-zinc ores have been completely decomposed in accordance with this invention,
and in precisely the manner and by means of the methods above described in
connection with galena. All the lead and silver and the whole or a considerable
portion of zinc contained in the ore are converted into the corresponding chlorides,
but the lead-zinc ores vary widely in their composition, so that some of them are
easily and readily decomposed by the above described mode of treatment, whereas
others require hydrochloric-acid gas to be passed through them for a greater length
of time. Moreover, lead-zinc ores differ from galena, and frequently contain a
mixture of silicious compounds and other porous bodies. If such is the case, they
may be decomposed even in the cold by moistening a ground mass of them with
water, and passing a current or stream of hydrochloric-acid gas through it without
mixing them with foreign bodies. Lead-zinc ore, which contained about equal
parts of lead sulphide, zinc sulphide and pyrites, has been treated successfully in
this way. To this end hydrochloric-acid gas is passed through the mass of the

page_text: previously-ground and moistened ore. Upon the completion of the reaction all the
lead and silver, about 40 per cent. of the zinc, and only traces of pyrites were
decomposed in the cold. It may be remarked, however, that the addition of a
foreign body considerably accelerates the decomposition of the zinc sulphide,
especially when the added body is ainmonium chloride. All the zinc sulphide can
also be decomposed.
It has been stated that in the present invention a double salt of lead and the:
base of the chloride used is formed. Conditions requisite for the formation of a
double salt are present in my invention and require that the added chloride should!
be compelled to assume or be of solid form. To this end the added chloride must.
either be used as a solid in which case it is dissolved little by little and precipitated
along with lead chloride, or if used in solution it must be treated with hydrochloric-
acid gas, in such case it is thrown down because it is less soluble as the solution
becomes more acid. It will be seen that the above mentioned conditions preclude
the presence of such a large quantity of aqueous solution as would destroy the
double salt.
After the ore has been decomposed by any of the methods above described, the
resultant mass is freed from adhering acid and hydrogen sulphide. Various
methods may be employed for this purpose; for example, the mass may be
removed from the vessel in which it was treated with hydrochloric acid and
permitted to remain in another vessel and in communication with the air for two
or three days. During this time hydrochloric acid which adhered to the mass
continues to act on the ore if any of it is left undecomposed and the remaining
hydrochloric acid together with the hydrogen sulphide diffused. If the ore was
decomposed by means of gaseous hydrochloric acid, the resultant mass may be
freed from adhering acid by means of a current of air.
The mass obtained from lead ores by the action of hydrochloric acid in the
presence of a base chloride consists of double chloride of lead and the base of the
added chloride, other chlorides formed from the other metals coutained in the ore,
and impurities such as silicious compounds and the undecomposed sulphides as
iron-sulphide, zinc-sulphide, etc., and after having been freed from adhering
hydrochloric acid and hydrogen sulphide, is leached with water. The added
chloride as well as the other soluble chlorides formed in the reaction are obtained
in solution. Even the silver chloride if silver compounds were present in the ore
goes into the solution because of its solubility in most concentrated chloride
solutions, particularly in solutions of the chlorides of calcium, magnesium and
ammonium, which, as has been stated, are well adapted for use in the decomposition
of lead ores.
In the leaching operation use is made of as much water as is
necessary for dissolving out the easily soluble chlorides. Almost all of the lead
chloride remains in the solid state because of its great insolubility in most chloride
solutions, especially when the latter are not concentrated. Only traces of the lead
chloride go into the leaching solution.
The lead-chloride left over after the leaching process may be used if it be
sufficiently pure or if impurities would not interfere with the intended use of it..
However, if desired, the lead-chloride may be purified by placing it in a con-
centrated solution of magnesium-chloride, calcium-chloride, ammonium-chloride or
any other chloride capable of producing a double salt with lead-chloride. Upon
boiling and stirring, comparatively large quantities of lead-chloride are dissolved.
The solution may then be filtered to free it from impurities and cooled or
permitted to become cold, whereupon lead-chloride is thrown down as such, or as
a double salt consisting of lead-chloride and the chloride used for the process.
of re-crystallization. The composition of the salt obtained by the foregoing
re-crystallization depends upon the degree of concentration of the solution employed,
and from which it is crystallized as will be more readily understood from the
description which will be presently given. The re-crystallized lead-chloride may
be washed with water in order to free it from the adhering or crystallized.
chloride employed and is then dried. The mother liquid may be used over and

page_text: over again and successively heated and cooled for the purpose of treating fresh
charges of lead-chloride. It has been stated that the composition of the
re-crystallized salt depends upon the degree of concentration of the chloride
solution employed, and in order that this may be fully explained, it will be
assumed that chloride of leal is to be re-crystallized by dissolving, beating and
cooling it in a solution of calcium-chloride. A boiling calcium-chloride solution of
about 45 degrees Baume, dissolves 250 grammes of lead-chioride for each litre of
solution. Upon cooling, 70 per cent. of the quantity of lead-chloride dissolved is
thrown down as crystals and 30 per cent. or 75 grainmes of the lead-chloride_per
litre remains in the solution, of which the strength is therefore increased to
49 degrees Baume. The crystals thrown down consist usually of 84 per cent. of lead-
coloride, 8 per cent. of calcium-chloride and 8 per cent. of water, and appear to
represent a mixture of many different double salts of lead-chloride and calcium-
chloride, and it may be remarked that the crystals thrown down at the beginning
of the cooling operation contain more lead-chloride and less calcium-chloride and
water than do those which are thrown down at the end of the cooling operation.
If the hot solution of calcium-chloride after lead-chloride shall have been dissolved
in it is first diluted with water and afterward cooled, then in such case the crystals
contain little or no calcium-chloride and less lead-chloride is retained in the cooled
solution. In practice good results have been obtained by using a concentrated
solution of calcium-chloride which has been previously used for re-crystallization as
described, and therefore contains about 75 grammes of lead-chloride per litre and
such a solution measures about 49 degrees Baume. This solution is heated,
substantially to the boiling point, and lead-chloride is thrown into it. Each litre
of solution is capable of dissolving 175 grammes of lead-chloride. The solution is
then forced through an externally heated filter in order to free it from insoluble
impurities and is finally cooled off, whereupon all the lead-chloride (175 gramines
per litre) which was previously dissolved is thrown down in crystals consisting of
double salts of lead-chloride and calcium-chloride. The remaining solution may
be drawn off and again used in the same manner. The crystals are washed with
water, which dissolves the calcium-chloride of the double salt, and pure lead-
chloride is thus obtained. The above mode of procedure is subject to modification ;
for example, before the solution is cooled it may be diluted with water, and good
practical results have been obtained by adding 190 cubic centimeters for each litre
of solution. When this is done the amount of lead-chloride thrown down is
the same as before, but the crystals contain less calcium-chloride, only about
per cent.
2
As above described the process of leaching precedes the
process of
re-crystallization, but in some cases these two processes may be performed in a
single operation, especially if the same chloride of a base is used for the
decomposition as well as for the re-crystallization. In such case the mass
consisting of the decomposed ore and the added chloride of a base is placed in a
hot concentrated solution of the chloride of the same base. The chlorides
including lead-chloride dissolve in the solution and are separated from the
insoluble part and filtered. Upon cooling, chloride of lead is thrown down as a
crystalline mass. All the other chlorides remain in solution and may be finally
precipitated as oxides by means of an oxide.
In the decomposition of lead-zinc or lead ores by means of hydrochloric-acid gas
in the presence of a chemically indifferent body either added or naturally contained
in the ore, the re-crystallization of the resulting lead-chloride is best accomplished
by preliminarily leaching out the formed zinc-chloride as well as all other metal
chlorides easily soluble in water, including the formed silver-chloride which is
readily dissolved in a zinc-chloride solution. The mixture which is left after
leaching consists of lead-chloride, undecomposed zinc and iron compounds,
silicious gangue, etc., together with the chemically inert substance if it were
added. From this mixture lead-chloride may be extracted by re-crystallization in
the manner described and by means of a solution of a chloride of a base.

page_text: With regard to the leaching operation, it may be remarked that the presence of
zinc-chloride in the solution is advantageous because it diminishes the solubility of
lead-chloride in water. Therefore zinc-chloride may be leached out and obtained
almost free from lead-chloride. The solubility of lead-chloride decreases in
proportion to the strength of the zinc-chloride solution and a maximum of
insolubility appears to be reached when the solution contains about 12 per cent. by
weight of zinc-chloride. At this particular strength of solution, lead-chloride is
about six times less soluble than in pure water.
It will be obvious to those skilled in the art that modifications may be made
without departing from the spirit of this invention, hence the same is not limited
to the details herein set forth, but
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondents, and in what manner the
same is to be performed, I declare that what I claim is :
1. The process of decomposing a mass of lead-zine ores which consists in
converting lead, zinc and silver sulphides into chlorides by means of hydrochloric
acid, recovering the zinc and silver chlorides from the mass by leaching it, and
recovering lead chloride from the mass by re-crystallizing it from a hot saline
solution which is subsequently cooled, substantially as described.
2. The process of decomposing a mass of lead-zinc ores which consists in
converting its sulphides into chlorides by means of hydrochloric acid, then leaching
the mass to remove some of the chlorides, then treating the mass with a hot saline
solution to remove lead-chloride, which is recovered upon cooling the hot solution,
substantially as described.
3. In the reduction of lead and lead-zinc ores by means of hydrochloric acid,
that improvement which consists in forming therefrom solid double salt of lead,
and a base by presenting solid chloride of said base to the lead sulphide contained
in the ore during its conversion into chloride by the action of the acid, substantially
as described.
4. The process of decomposing lead and lead-zinc ores which consists in mixing
the pulverized ore with a chloride in solid state, and treating the solid mixture with
hydrochloric acid, whereby the process may be practiced even in the cold, and
produces a solid admixture or double salt of lead-chloride and the added chloride,
substantially as described.
5. In the reduction of lead and lead-zinc ores, the process which consists in
effecting the direct combination of the acid radical of hydrochloric acid with the
basic radical of the sulphides contained in the ores by mixing the pulverized ore
with a pulverized substance or material, moistening the mixture with water, and
treating the mixture with hydrochloric-acid gas, substantially as described.
6. In the reduction of lead and lead-zinc ores, the process which consists in
effecting the direct combination of the acid radical of hydrochloric acid with the
basic radical of the sulphides present in the ores by mixing the pulverized ore
with a pulverized chloride containing water, and treating the mixture with
hydrochloric-acid gas, substantially as described.
7. In the reduction of lead and lead-zinc ores, the process which consists in
effecting the direct combination of the acid radical of hydrochloric acid with the
basic radical of the sulphides present by moistening the pulverized ore with water,
and treating it with hydrochloric-acid gas, substantially as described.
8. In the reduction of lead and lead-zinc ores, the process which consists in
forming therefrom a chemical composition or admixture consisting of two salts
whereof one is chloride of lead and the other is a chloride of another base by
mixing the pulverized ore with a chloride of a base and treating the mixture with
hydrochloric acid, and recovering solid lead chloride by drying this composition
and leaching out the added chloride, substantially as described.
9. In the reduction of lead and lead-zinc ores, the process which consists in
forming therefrom a chemical composition or admixture consisting of a salt of lead

page_text: and a second salt, and recovering solid salt of lead by drying this composition and
Jeaching out the second salt, substantially as described.
10 The herein described process which consists in dissolving comparatively
large quantities of lead salts by means of a comparatively small quantity of a
heated solution of salts forming with the lead salts a double salt, and then cooling
said solution to effect re-crystallization, substantially as described.
11. The herein described process which consists in dissolving comparatively
large quantities of chloride of lead by means of a comparatively small quantity of
a heated solution of a chloride, and then cooling said solution to precipitate salt of
lead, substantially as described.
12. The process of decomposing lead ores which consists in forming therefrom a
chemical compound consisting of salt of lead and a second salt by means of
hydrochloric acid and the second salt, freeing said composition from adhering gases
by expelling the same, purifying the composition by re-crystallizing it from a saline
solution of which the temperature is changed, and recovering the lead salt by
leaching out said second salt, substantially as described.
13. The herein described process which consists in decomposing lead ores by
bydrochloric acid in the presence of a chloride, and separating the formed double
chloride from adhering acid by drying it, substantially as described.
14. In the process of decomposing lead ores, that improvement which consists in
converting sulphides directly into chlorides by treating the ore with hydrochloric-
acid gas or vapor and recovering the pure hydrogen sulphide produced, substantially
as described.
15. The within described process of separating zinc-chloride and lead-chloride
from each other which consists in leaching a mixture of these chlorides with water
which dissolves the zinc-chloride leaving lead-chloride which in the presence of
zinc-chloride is practically insoluble, substantially as described.
Dated this 16th day of February 1897.
BOULT & WADE,
Agents for the Applicant.