IMPROVEMENTS IN THE TREATMENT OF METALLIC SULPHIDES
Year: 1879

page_text: LETTERS PATENT to John Berger Spence, of Lombard Street, in the City of
London, Merchant; for the Invention of "IMPROVEMENTS IN THE TREATMENT
OF METALLIC SULPHIDES."
Sealed the 18th November 1879, and dated the 20th May 1879.
PROVISIONAL SPECIFICATION left by the said John Berger Spence at the
Office of the Commissioners of Patents on the 20th May 1879.
JOHN BERGER SPENCE, of Lombard Street, in the City of London, Merchant.
"IMPROVEMENTS IN THE TREATMENT OF METALLIC SULPHIDES."
My Invention consists in the conversion of metallic sulphides into metallic
sulphates, and the recovery of the gases produced therefrom.
I find that all metallic sulphides when ground to a fine powder can be dissolved by
sulphuric acid, and are then converted into metallic sulphates. When the acid is
dilute the action is much feebler than when it is in a concentrated condition, and in
the former case sulphuretted hydrogen is evolved, but when concentrated sul-
phuric acid is used a much more rapid action takes place, and sulphurous acid is
evolved.
When sulphuretted hydrogen is produced I use it for the precipitation of metallic
sulphides, or burn in connection with air, and convert it into sulphurous acid, or
take it up by oxides of iron or by other well known means, but in the case when I
use strong sulphuric acid, I produce sulphurous acid which I convey into vitriol
chambers for the manufacture of sulphuric acid.
My process refers to the treatment of all ores containing one or more metallic
sulphides, and to ores containing any metals, some of which may be metallic
sulphides.
In ores containing sulphides of the metals which form insoluble sulphates, they do
not enter into solution, but remain with the insoluble material, and may be treated
by well known means, as in the case of sulphate of lead and other insoluble
sulphates.
In cases where the ore is generally known as mixed ore, the sulphates made soluble
are separated by well known means.
I prefer in all cases to use boiling acid, and in some cases I make the ore into a
paste with sulphuric acid, and subject the mass to heat either in a retort or open

page_text: furnace, or what is called a muffled furnace. When it is treated in a retort I obtain
sulphur.
When treating sulphides by this process I find that arsenic is also evolved, and
the arsenic so given off I condense in suitable chambers.
My Invention also consists in the treatment of mixed sulphides of the metals by
hydrocoloric acid. If the ore is reduced to a sufficiently fine powder, the whole of
the sulphides are converted into chlorides, from which they are separated by well
known means. The sulphuretted hydrogen evolved I utilize for the purpose of
precipitating sulphides, or I pass it through oxide of iron or other oxides, or burn
it with air for producing sulphurous acid, and condense in vitriol chambers as
sulphuric acid.
Another part of my Invention consists in the production of a pigment for paint,
and I prefer to use those sulphides of the metals which are mainly composed of
sulphide of lead and zinc. grind these ores to a fine powder, and add sulphuric
acid or hydrocoloric acid in such quantities that the ore shall not be reduced to
solution but sufficient to form a pasty mass. When the action of the acid ceases
the mass becomes dry, and it may then be ground to powder and used as a pigment
for paint.
Another mode of obtaining a pigment for paint is to grind the metallic sulphides
with sulphur.
Another part of my Invention consists in grinding the metallic sulphides to a
fine powder, and for this I prefer to use those ores mainly composed of lead and
zinc. I then mix intimately with sulphuric acid until a paste is formed. I then
subject this to heat, either in a close or open furnace, the gases evolved being utilized
as before described. The mass will then be found to consist chiefly of anhydrous
sulphates, which I grind to powder and convert into a pigment for paint.

page_text: "
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Berger Spence in the Great Seal Patent Office on the 20th
November 1879.
JOHN BERGER SPENCE, of Lombard Street, in the City of London, Merchant.
'IMPROVEMENTS IN THE TREATMENT OF METALLIC SULPHIDES."
The object of my Invention is so to treat metallic sulphides as to obtain useful
products therefrom. Hitherto many of the metallic sulphides have been practically
of little use, as the difficulties experienced in treating them have been considerable.
I have however found that all metallic sulphides, when crushed or ground to an
impalpable powder, are readily dissolved by sulphuric acid, and are thus rendered
capable of being applied to various useful purposes. The powdered sulphides when
treated with sulphuric acid are converted into sulphates. According to the strength
of the acid various bye-products will be obtained; thus when dilute sulphuric acid
is employed sulphuretted hydrogen is evolved, but when concentrated sulphuric acid
is used, a more rapid action takes place and sulphurous acid is evolved. The
sulphuretted hydrogen produced may be used for the precipitation of metallic
sulphides, or burnt in connection with air and converted into sulphurous acid, or it
may be taken up by oxides of iron, or treated in any other well known manner.
The sulphurous acid evolved upon treatment with the stronger acid I convey into
vitriol chambers for the manufacture of sulphuric acid. In all cases I prefer to boil
the metallic sulphides in the acid.
The sulphates of the metals may also be produced by mixing the powdered
sulphides with sufficient strong sulphuric acid to make a pasty mass, which I
subject to heat in a retort until the conversion is effected. By this mode of treat-
ment sulphur is given off, which is collected in any suitable manner.
The quantity
of the sulphuric acid used will vary according to the richness of the metals contained
in the ore.
My process refers to the treatment of all ores containing metallic sulphides alone
or mixed with other substances.
Some of these sulphides will when converted form insoluble sulphates, and these
may be treated by well known means, as in the case of sulphate of lead and other
insoluble sulphates. The soluble sulphates are separated by well known means.
When treating sulphides by these processes I find that arsenic is evolved, and the
arsenic so given off I condense in any suitable manner.
My Invention is also applicable to the production of a pigment for paint. For
this purpose I prefer to use those sulphides of the metals which are mainly com-
posed of sulphide of lead and zinc. These ores I grind to a fine powder, as before,
and add thereto sulphuric acid in such quantity as to form a pasty mass. When
the action of the acid ceases the mass will become dry, and it may be then ground
to an impalpable powder and used as a pigment for paint. Or the pasty mass may
be subjected to heat either in a close or open furnace before being finally ground up.
The gases evolved during this operation will be utilized as before described. After
burning I grind the mass (which will be found to consist chiefly of anhydrous
sulphates) to an impalpable powder to be used as a pigment for paint.
A similar result may be obtained by grinding up the metallic sulphides with
sulphur.
Having now described the nature of my Invention for "Improvements in the
Treatment of Metallic Sulphides," and explained the manner of carrying the same
into effect, I wish it to be understood that under the above in part recited Letters
Patent I claim,--
First. Treating metallic sulphides as herein described for the purpose of converting
them into sulphates of the same metals, and obtaining other useful products
therefrom.

page_text: Second. The mode or modes herein described of treating metallic sulphides for the
purpose of producing a pigment for paint.
In witness whereof, I, the said John Berger Spence; have hereunto set my
hand and seal, the Twentieth day of November, in the year of our Lord
One thousand eight hundred and seventy nine.
J. BERGER SPENCE. (L.S.)