Improvements in the Concentration of Pyritic Ores, some Con- stituents of which are Removed by Hydrochloric Acid, with or without the Addition of Haloid Salts of the Alkalies or Alkaline Earths.
Year: 1891

page_text: Date of Application, 15th Oct., 1891
Complete Specification Left, 15th July, 1892-Accepted, 15th Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Concentration of Pyritic Ores, some Con-
stituents of which are Removed by Hydrochloric Acid, with or
without the Addition of Haloid Salts of the Alkalies or Alkaline
Earths.
I, HENRY WESTON WALLIS, Analytical Chemist & Assayer, in the Laboratory
of the City Institute, 30-32 Ludgate Hill E.C. do hereby declare the nature of
this invention to be as follows:-
I treat the ground ore with hydrochloric acid, hot or cold, lixiviate, and by
ordinary processes of smelting or humid extraction, treat the residue, which is the
concentrate, for whatever valuable minerals it may contain.
The solution obtained by lixiviation, should it contain anything valuable, I also
view as a concentrate, and treat it by whatever methods may seem advisable.
Should the ore not contain metals of the alkalies or alkaline earths, it may be
advisable with certain kinds of ores to add to the hydrochloric acid, a haloid
compound of an alkali or alkaline earth, then treat with hydrochloric acid and
lixiviate &c.
Dated this 15th day of October 1891.
HENRY WESTON WALL
COMPLETE SPECIFICATION.
Improvements in the Concentration of Pyritic Ores, some Con-
stituents of which are Removed by Hydrochloric Acid, with or
without the Addition of Haloid Salts of the Alkalies or Alkaline
Earths.
I, HENRY WESTON WALLIS, Analytical Chemist & Assayer, formerly of
32 Ludgate Hill, London, E.C., now of 8 Great Winchester Street London E.C. 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:-
By this process the ore is taken in the state it comes from the ore-breaker and
treated with hydrochloric acid.
If the ore contains pyrites in a form not readily attacked by hydrochloric acid,
the ore should be raised to a temperature below that of redness before being
subjected to the action of the acid: by this means the refractory pyrites is trans-
formed into forms of pyrites more amenable to acid treatment.
This preliminary heating of the ore should be conducted without free access
of air.
The ore is treated with hydrochloric acid for the purpose of producing an
evolution of sulphuretted hydrogen, whereby a separation between the constituents
of the ore is effected.
The action may in many cases be advantageously promoted by boiling the ore in
the acid, though the application of heat in this part of my process is not
essential.
Treatment with hydrochloric acid may be continued for an hour or more, the
supernatant liquor is then drawn off and the residue washed and dried.
The residue, which in many instances has weighed less than one quarter of the
charge of ore at first taken, will be found to contain nearly all, if not the whole

page_text: of any silver, gold, copper, in the ore, together with those metals whose sulphides
are insoluble in dilute acid solutions.
The supernatant liquor will be found, to contain a very large proportion of
whatever other heavy metals may have been, present in the ore, together with
soluble silica and its congeners as well as the alkaline earths and alkalies.
The liquor may be used again and again, with fresh charges of ore, provided
the strength of acid is sufficiently maintained, by the addition of more con
centrated acid or of anhydrous acid.
The less soluble constituents of the liquor may be removed from time to time
by crystallization or precipitation, as expediency & circumstance may direct.
If the ore to be concentrated, contains no sulphides which yield sulphureted
hydrogen when treated with hydrochloric acid, or if the ore does not contain such
sulphides in quantities sufficient to provide sulphuretted hydrogen enough for the
purpose of separation; an adequate quantity of an artificial sulphide or of another
ore containing excess of such sulphides, must be introduced.
It is for instance advantageous by my process, to concentrate weathered pyrites
in company and mixed with unweathered pyrites.
The treatment with acid effects the reduction & solution of peroxides and per-
salts, by means of the sulphuretted hydrogen which is evolved. I prefer to use
hydrochloric acid, rather than any other acid capable of producing sulphureted
hydrogen from the ore, because hydrochloric acid is the most rapid in its action, and
because its action is not likely to introduce difficulties in the subsequent extraction
of metals from the concentrated ore, but in situations where hydrochloric acid is
difficult to obtain, sulphuric acid may be used in place, of it.
Chlorides of alkalies and alkaline earths greatly promote the solution of chlorides
of lead, and in cases where it is desirable to remove the lead completely from the
solid concentrate or residue, these chlorides should be added, if their bases are
originally absent from the, ore, the, chlorides being generally the cheapest of haloid
salts.
During the treatment with acid, a voluminous dark green substance collects,
which partly floats on the surface and partly subsides.
"
On heating, this substance condenses, sinks and hardens; it is probably due to
the formation of that allotropic form of sulphur known as "liquid
mechanically encloses, iron, copper, gold, silver, arsenic, antimony, nickel and
sulphur, this
cobalt, compounds, combining with these metals and forming a compound of
constant composition, somewhat similar to arsenical pyrites. I know, of no method
at present of avoiding the production of this compound, but on baking a second
time, after the treatment with acid and then again treating in the same liquor, this
tendency to reform, pyrites is partially overcome & further. concentration is
effected.
As a particular instance of the application of my process, and of the quantities
used and obtained when operating upon one ton of ore: I proceeded as follows.
Having heated the ore to a temperature below that of redness & discharged it into
the acid (aqueous hydrochloric acid) the solid residue amounted to 22-69 per cent.
of the ore taken.
After baking a second time and treating again with the same liquor, the solid
residue was reduced to 17.84 per cent. of the ore, at first taken.
Thus a ton of ore is reduced to, 3 cwt., 2. qrs., 7-616 lbs.
Next as to the quantities used :-
The appended table shows, that against 39-6 parts. of iron, 14 of lead, 9 of
manganese, 27 of lime, and 28 of magnesia: 53 61 parts, of anhydrous, acid is,
theoretically required.
aqueous
This quantity is, obtained in, 2 tons, 2 cwt., 2. qrs., 3.136 lbs. of,
hydrochloric acid of 25 per cent. strength, or in 1 top, 15. cwt., 1 qrs., 21-28 lbs.
of hydrochloric acid of 30 per cent. strength. Thus, from 2 to 21 tons of
aqueous hydrochloric acid of strength varying between 25 & 30 per cent. is sufficient,
to concentrate this particular ore.
г "

page_text: of iron.
my vamping PP
DOMIC CALCULATO
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that
what I claim is :
(i.) The application of acids to the concentration of pyritic ores, as substantially
set forth.
(ii.) The conversion by heat of refractory pyrites which are not decomposed by
acid, into forms of pyrites which are so decomposed, for the purpose of concentration,
as substantially set forth.
(iii.) The utilization of the functions of sulphuretted hydrogen as a precipitant
of some sulphides in acid solution, and reducer of peroxides & persalts, for the
purpose of ore concentration-said sulphuretted hydrogen being generated from
the ore itself, or from another ore, or artificial sulphide added thereto, as sub-
stantially set forth.
(iiii.) The concentration of one ore by another, with the help of acid-both ores
being thereby concentrated.