Improvements in Hydro-metallurgical Processes.
Year: 1889

page_text: Date of Application, 16th Jan., 1889
Complete Specification Left 15th Oct. 1882-Accented. 16th Apr. 1890
PROVISIONAL SPECIFICATION.
Improvements in Hydro-metallurgical Processes.
I, JASPER HENRY SELWYN of 16 Gloucester Crescent, Hyde Park, in the County of
Middlesex, Admiral, do hereby declare the nature of this invention to be as follows:-
My invention consists of improvements in the processes of humid metallurgy by
which the recovery of metals and metalloids from their ores is rendered less expensive..
and more perfect. The improvement is effected by the use in solutions of the nitrates
or nitrites of the alkaline metals in combination with di-chloride or chloride of sulphur,
or the impure nitrates, as occurring naturally, may be used in combination with
hydrochloric acid, chloride of sodium, sodium hypo-sulphite or any other well known
solvent, but in almost all cases the object of complete extraction of the valuable sub-
stances is effected without the preliminary chloridising roasting now considered
necessary and therefore at considerably less expenditure of time and money.
Dated this 16th day of January 1889.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Hydro-metallurgical Processes.
I, JASPER HENRY SELWYN, of 16 Gloucester Crescent, Hyde Park, in the County
of Middlesex, Admiral, 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:-
My invention consists of improvements in the processes of humid metallurgy by "
which the recovery of metals and metalloids from their ores is rendered less expensive
and more perfect than heretofore.
Humid processes of metallurgy as heretofore practised where refractory ores are to
be treated, involve a preliminary roasting with or without an addition of salt. This
occupies a considerable time, involves the necessity of skilled labour, and often results
in great losses of the precious metals, besides causing a nuisance to the neighbourhood
in which the process is carried on from the evolved destructive and poisonous gases.
Now the object of my invention is to obviate the necessity of this roasting and at a
less expense to give higher returns of the metal and other valuable substances con-
tained in the ores. To this end I use a solution of a nitrate or nitrite which may with
advantage be that of an alkali metal in combination with S, Cl, variously called
dichloride of sulphur, chloride of sulphur, and mono-chloride of sulphur and hereinafter
called dichloride of sulphur with a bath of salt solution nearly saturated. The impure
nitrates as occurring naturally may be used as the other salts present do not seriously
interfere with the desired action. Hydro-chloric acid, sodium hypo-sulphite, sulphate
of copper, or any other well known solvent may be used in conjunction with the
dichloride of sulphur and the nitrates or nitrites, in the bath.
The chemical reactions which take place in the vats in my process apparently result
in the production of nascent nitro-hydrochloric acid, or aqua regia, and sulphate of
soda as well as of free sulphur, besides chlorine and nitrous acid gas in excess, and
practically ensure the solution of all or nearly all of the metals and metalloids con-
tained in the ore.
In carrying out my invention it is to be understood that as with other humid
processes the ore must first be comminuted by crushing or stamping, screens being
used of from 10 to 40 holes to the linear inch according to the nature of the ore. A
greater subdivision is advantageous as regards all but the difficulty of filtering slimes
and the time taken.

page_text: The ordinary plant of vats or barrels such as are usually employed in humid
metallurgy or hydro-metallurgical processes is available for carrying out my invention
but covers or hoods for the double purpose of confining and collecting the escaping
gases consisting principally of chlorine, and nitrous acid, should be provided on the
vats as this collection enables the operator to regenerate the di-chloride of sulphur and
the hydro-chloric acid as well as to strengthen the nitric solution.
In carrying out my invention, a convenient way (which however is not invariable
because sometimes the ore may first be introduced) is to make in the vat or vata. a
strong nearly saturated solution of brine and to add to this about 5% (five per cent.)
of hydrochloric acid and from about 10% (ten per cent.) to 15% (fifteen per cent.) of
the nitrate or nitrite employed, which is in most cases nitrate of soda or, where
naturally existing in the country, it may then be nitrate of potash. There is next
introduced into the solution such a proportion of the di-chloride-of-sulphur--asis
required by the nature of the ore; this will be a small percentage only of the solution
and will not be the same for all ores and must be decided by previous analysis of the
particular ore to be treated and experiment thorewith in the laboratory. Any pro-
portion of dichloride of sulphur, say from 1% to 30% of the solution, which proves
sufficient to start the reactions and raise the temperature, may be used, both chlorine
and sulphur being recoverable to regenerate dichloride of sulphur. The addition of
the dichloride of sulphur is best made. in portions at intervals and not all at once.
The vat should only contain enough solution to leave a considerable margin in it
for rapid chemical action which will ensue on the introduction of the ore with great
rise of temperature. Sulphurous or sulphuric oxides or acids may in some cases be
used either-in-addition-to-or-in substitution for the S, Cl, but with arsenical-ores
care must be taken to avoid any possible production of arseniuretted hydrogen which
is highly dangerous. The solution-should-be-made-hot by steam or otherwise or hot
water may be employed from the beginning and a steam coil of pipe under the
filter bed or in the boiling vat, as is well understood, may be employed to keep
up the heat during the time required for the full-action of the solution on the ore.
With some ores no filter bed will be necessary in the boiling vat, and a floating
syphon may be employed to draw off the solution. The full action may be completed
in from one hour in the case of some ores to eight or more hours with others. Tests
may be made from time to time in the usual manner to see how far the solution of
the metals has been carried, and to ascertain that no valuable metal is mechanically
mixed with the sulphur. As soon as these tests shew satisfactory results, the filtration
can begin, but all floating sulphur should be collected first by skimming with wooden
shovels, cane sieves, or other simple means, all metallic substances being strictly
avoided. As the sulphur will be nearly pure and will be evolved in large quantities
from pyritous ores it is obvious that ores may be treated by my process expressly for
the manufacture of sulphur where no metals of any great value are found in them.
It is preferable to introduce the ore at intervals as the boiling goes on because in this
way each particle of ore in its descent will be attacked, and a too rapid action will bo
rendered less probable. For this purpose the covers or hoods may be raised and at
this time the above mentioned tests can be conveniently made. The operator must
carefully avoid the generation of such gases as may re-precipitate the metals in
the ore as for instance sulphuretted hydrogen. But many ores may be put in as
usual and the solution will not act rapidly on them until the dichloride of sulphur is
introduced. The solution containing the metals is to be filtered off in the usual
manner into the first precipitating tank and there in the case of ores containing gold
the gold is precipitated by any of the well-known means; this can be advantageously
done by the use of sulphuretted hydrogen gas or by electric currents with gold or
platinum and carbon electrodes as these will not cause any serious dilution or other
change in the solution. The residue or tailings may be tipped shovelled or sluiced
out as usual. As soon as the gold is all preeipitated the solution can be run off by
a floating syphon so arranged as not to disturb the precipitate; a wooden float with
legs being very suitable; the syphon taking the solution from above, not from below,
through a hole in the float into a second precipitating tank where a similar precipitation

page_text: of the silver by electricity with silver and copper electrodes or by the ordinary
sulphide of sodium will leave the solution deprived of its silver and ready for drawing
off into a third tank, in which if copper be present that metal is to be precipitated
by any of the well-known means or by an electric current with iron and copper
electrodes. The solution is now supposed in the case of a gold, silver and copper ore.
to have been deprived of all its metals, and is to be sent on into a sump, and then
tested and restored by additional salt or otherwise as is well understood to its standard
condition. Iron or other impurity may also at this time be precipitated or otherwise
got rid of, and if there be lead in the solution it may be recovered as corbonate, if
desired by the use of carbonate of soda. This can be obtained by roasting the
sulphate of soda (which will be one of the residual products) with charcoal or coal
and lime as well understood. The dichloride of sulphur can also be re-made from the
sulphur collected, in the usual manner, by burning it in the collected chlorine gas,
and condensing.
Thus the whole process can be conducted with very little expenditure of salt and is.
otherwise thoroughly recuperative.
When bismuth is a considerable constituent of the ore, it may be found preferable
to dilute the first filtrate which contains it with water which will precipitate the
bismuth, and thereafter to make a fresh solution for the treatment to obtain the
precious metals; and there may be other metals as tellurium, selenium, and antimony,
which will pay for special extraction from the solution; but such details for no part
of my invention.
Although I have tested my invention in connection with numerous refractory ores,
only in one instance where the ore was a very refractory one from Queensland have
I found it necessary to adopt any variation in the process. In this ore the gold is
apparently in a state which has been described by Latour de Breuil and Skey (see
Watts Chemical Dictionary) as gold coated with an adherent but invisible film of
sulphur which resists all ordinary treatment. In treating this ore by my process after
a first boiling which extracts all the bismuth present, the residue which is much less
in quantity than the original ore, has to be ignited, but not roasted, in order to
extract the gold and silver by a second boiling. By igniting it will be understood
that the process consists in hoating for a short time below redness on iron plates such
as are commonly used for drying ore before or after wet crushing.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. For the purpose of recovering metals or metalloids or both from their ores or
combinations the use of dichloride of sulphur, in combination with a nitrate or nitrite
in a bath of chloride of sodium or other suitable solvent as set forth.
2. The use of any of the well-known solvents of metal such as hypo-sulphite of
soda, hydrochloric acid or cupric sulphate in combination with the chloride of sulphur
and the nitrate or uitrite referred to in the precoding claim in a bath as above.
3. The manufacture of sulphur from pyritous ores in the manner set forth.
4. The use for the purposes specified, and in combination with nitrates or nitrites
in solution, of substances such as S, Cl, which will will produce nascent chlorine.
5. The mothod or process of recovering metals or metalloids or both from refractory
ores without roasting as described.
6. In the treatment of refractory ores by the humid process completely oxidising
and chloridising the otherwise refractory metals and liberating the excess of sulphur
thereby dispensing with preliminary roasting by causing nitric hydrochloric and
sulphuric acids to be evolved in a nascent state as set forth.
Dated thi ish i 1000
W. Lloyd Wise,
J. H. SELWYN.
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.