IMPROVEMENTS IN THE TREATMENT OF ORES AND MINERALS FOR THE PURPOSE OF OBTAINING USEFUL PRODUCTS THEREFROM
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Benjamin Tanner at the Office
of the Commissioners of Patents, with his Petition, on the 25th
January 1875.
I, BENJAMIN TANNER, F.C.S., of Dublin, Ireland, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN THE TREATMENT OF
ORES AND MINERALS FOR THE PURPOSE OF OBTAINING USEFUL PRODUCTS THEREFROM,"
to be as follows:-
This Invention consists in the treatment of ores and minerals, which
contain as component parts thereof zinc, lead, copper, silver, gold, iron,
and sulphur, or one or more of such substances, so as to obtain useful
and valuable products therefrom in an economical manner.
A mineral containing the above-mentioned substances occurs largely
in many localities, and especially in the Isle of Anglesea, where it is
known by the name of "bluestone," but which has not hitherto been
worked on a commercial scale on account of the practical difficulties
which have been attendant upon its reduction by the methods proviously
adopted for the separation of the component parts thereof. These
difficulties are overcome by means of the processes which form the

page_text: subject of the present Invention, in which the chief advantage consists
in the separation of zinc and lead from the ore or mineral under
treatment.
"
It should be mentioned that although in this Specification processes
are described for the extraction of zinc and lead from a mineral which t
has all the above-mentioned metals present, the same principle is equally
applicable to any ores or minerals containing zinc or lead, or any lesser
number or combination of such before-mentioned or other metals.
The mineral under treatment, either with or without previous roasting
or calcining, is by preference first reduced to a state of fine division by
any suitable means. It is then treated with hydrochloric or sulphuric
acid (in any more or less pure or concentrated condition) or with chloride
of sodium or other chlorides or sulphates or any mixtures thereof capable
of bringing the zinc and lead into a soluble condition (as will bo
understood by persons conversant with the chemical treatment of metals:
and metallic compounds and the effect of the reagents employed in such
cases), with or without the employment of water or the application of
heat, but it is preferred either to raise the temperature or to boil or fuse
the mixture, as by these means the reaction takes place more quickly
and completely; take, as an example, the treatment of the mineral with
hydrochloric acid without having previously roasted or calcined it.
The mineral having been reduced to any suitable degree of fineness by
any convenient means, is transferred to the decomposing tank and there
intermixed with hydrochloric acid (of any desired strength), and the
temperature of the mixture, by preference, raised either by the use of
steam or otherwise, the temperature being regulated as may be desired.
Sulphuretted hydrogen gas is given off, whilst zinc together with more or
less of the lead is converted into chloride.
i
When the escape of gas slackens the temperature may with advantage
be increased, and when the gas ceases to come off or when the acid
employed is saturated, the solution is removed.
If on testing the residue with hydrochloric acid, either sulphuretted
hydrogen gas is given off or more zinc dissolves, then more hydrochloric.
acid is added to the residue, which addition may be repeated as often as
is necessary, or the required quantity of the acid having been ascertained
it may be added in one operation, subsequently testing the residue as
above described.

page_text: In some cases it is desirable (when the solution ready for running
away from the mineral contains any of the acid unsaturated) to pass it
into a vessel containing either fresh mineral or partially exhausted
mineral, either with or without first subjecting each to a roasting or
calcining operation or any mixture thercof, so as to more completely
saturate the acid either with or without the application of heat.
The resulting solution, ready for removal in either of the above-
mentioned operations, may be conveyed to a settling tank for the
purpose of crystallizing out the chloride or chlorides which separate on
cooling or dilution, or the said solution may be run direct to the vessel
employed for the separation of the lead.
In some cases it is advantageous to keep the solution separate from the
washings of the residue in the decomposing tank. In any case the lead
remaining in the solution (either with or without previous neutralization
of the solution by means of lime or carbonate of lime or otherwise) is
removed either by means of zinc or iron or proto-salts of iron, or
sulphuric acid, or sulphuretted hydrogen, or lime, or lime salts, using by
preference either iron or sulphuretted hydrogen, either with or without,.
but by preference with an increase of temperature, the lead is thus.
separated from the solution cither in the metallic form or in combination
with some acid or element.
In some cases (when the solution has been freed or nearly so from the
lead, as for example, by means of sulphuretted hydrogen) the solution,
by preference after filtration, decantation, or otherwise, and prior to the
removal of the zinc by cither of the methods herein mentioned, is made
to dissolve more of the raw material or the residue (cither with or.
without previous roasting or calcination), and the resulting solution then :
treated as herein set forth.
The solution freed from the lead will consist essentially of chloride of
zinc, and this is treated by supplying it with an excess of ammonia or
gas water, and then passing sulphuretted hydrogen through the mixture, .
either with or without previous filtration, having by preference first
brought the temperature of the mixture to or nearly to the boiling.
point.

page_text: the bulk of the zinc is separated, the remainder of the zinc being
subsequently removed by dilution with water, or by means of sulphuretted
hydrogen, taking care in the latter case that the solution has an alkaline
reaction on litmus. In either case the precipitate is washed either by
filtration, decantation, or otherwise, it being subsequently dried and in
some cases exposed to a high temperature, the same yielding a more or
less pure oxide of zinc, whilst the solution may be evaporated for the
purpose of obtaining the chloride of ammonium formed, and which may
be further purified in the ordinary manner.
In the event of any sulphate of zinc being formed during the process,
it is removed by means of water, by preference, at or near the boiling
point, and then either crystallized out or treated by either of the plans
herein mentioned.
The solution may also be treated with lime or magnesian limestone, or
carbonate of lime or of magnesia, or of the alkalics, or any mixtures
thereof, either with or without clevation or temperature, but it is
preferred to have the solution at or near the boiling point prior to the
admixture or during the decomposition, and by either of these means
the chloride of zinc is decomposed, such treatment resulting in the
precipation of the zine either as an oxide or as a carbonate or a mixture
thereof, whilst a chloride of the precipitate remains in solution and may
be recovered by the ordinary method. The zinc precipitates may then be
treated in the ordinary manner for the treatment of metallic zinc. The
residue in the decomposing tank is then washed either by water or
bydraulic acid (by preference at or near the boiling point), the chloride
of lead being thereby removed together with more or less of the
chloride of zinc, and the resulting solution is then treated by either
of the methods herein mentioned for the recovery of the lead and
zinc.
In some cases the chloride of lead is dissolved in the residue, with or
without the employment of heat, by means of strong hydrochloric acid,
and then the lead, having been precipated (as for example by sulphuretted
hydrogen), the hydrochloric acid is again ready to be employed for the
same purpose as for treating either the raw material or the residue,
either with or without previous roasting in the manner herein
mentioned.

page_text: Having removed the chlorides of lead and zinc, the residue may now
(with or without the same having been previously boiled or fused with
common salt and water) be roasted or calcined, and then treated with
either common salt or hydrochloric or sulphuric acid (in any more or
5 less pure or concentrated condition), or any mixtures thereof, with or
without the employment of water. The resulting solution is treated as
hcrein-after described :-The residue from the preceding operation may
now be fused or heated with common salt, and treated subscquently
in the ordinary manner adopted for the extraction of copper, silver, and
gold from burnt pyrites, subsequently drying and raising the temperature
so as to liberate the sulphur contained therein, and which may be
converted into sulphuric acid by the usual method; or the residue from
the decomposing tank may be dried and roasted with common salt, and
the soluble portion extracted by water, with or without the conjoint use
of hydrochloric or sulphuric acid or mixtures thereof, the residue being
subsequently treated with hydrochloric or sulphuric acid or mixtures
thercof, for further exhaustion of the mineral.
The solution's obtained at any of the foregoing stages may be treated
by any of the methods herein described, or in the ordinary methods
adopted for the separation of the metals contained therein, either singly
or together, and either in the metallic state or combined with some acid
or element.
Any separation of crystals from any of the foregoing solution may be
treated with hydrochloric acid or water, and the resulting solution
treated as herein-before described for the recovery of lead or zinc, or the
crystals may be mixed with water, or with hydrochloric acid, and then
subjected to the action of sulphuretted hydrogen gas, with or without the
application of heat.
The precipitate is washed either by filtration, decantation, or otherwise,
and the solution and washings treated as hercin-before described for the
recovery of the zinc.
Although hydrochloric and sulphuric acid or mixtures thereof have
been herein particularly mentioned, other acids capable of producing the
same results, and which will be well known to persons conversant with
the
Just

page_text: not so advantageously on account of their more costly character, and it
must also be distinctly understood that the residues herein-before
mentioned may be roasted, with or without common salt, at any stage of
the operation without departing from the principles of the present
Invention.