IMPROVEMENTS IN THE METHOD OF TREATING METAL- LIFEROUS SULPHURETS
Year: 1855

page_text: LETTERS PATENT to Homer Holland, of Westfield, in the County of
Hampden and State of Massachusetts, in the United States of America,
for the Invention of "IMPROVEMENTS IN THE METHOD OF TREATING METAL-
LIFEROUS SULPHURETS."
Sealed the 3rd November 1855, and dated the 22nd May 1855.
PROVISIONAL SPECIFICATION left by the said Homer Holland at the
Office of the Commissioners of Patents, with his Petition, on the 22nd
May 1855.
I, HOMER HOLLAND, of Westfield, in the County of Hampden, and State of
Massachusetts, United States of America, Physician, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE METHOD OF TREATING
METALLIFEROUS SULPHURETS" to be as follows:-
A quantity of nitrate of soda, as free as possible from any admixture with
other salts, is provided, together with a quantity of any metalliferous sulphuret,
both being separately or jointly finely pulverized, and then thoroughly mixed
together in a dry state, in the proportion of two hundred and ninety-one parts
of the nitrate of soda to every hundred parts of the sulphur previously
determined and known to exist in the ore to be operated upon. About one-
third part of this mixture must then be deflugrated in a large cast-iron basin,
having a concave sole or hearth heated from beneath to a moderate realness,
and at separate intervals of about half an hour each remaining two-thirds are

page_text: to be added while the mass in the basin is being thoroughly stirred and inter-
mixed. The basin must be so placed over the furnace or fire as to allow the
sulphurous acid fumes to pass into a sulphuric acid chamber through a copper
cap or alembic; then the heat, moderate at first, is gradually to be raised
until the sulphurous acid vapors have entirely passed off, and full oxidation
and redness of the ores is obtained. When cooled down, the silver and gold
previously contained in the ore will be found reduced to fine grains or particles,
which may be readily separated from the resolved and decomposed mass by
methods already well known.
When copper pyrites is decomposed and resolved by my process, the cooled
mass must be lixiviated with hot water, so as to dissolve the resulting sulphates
of copper and soda; and from this solution the sulphate of copper may be
obtained in a crystalline form or galvanic copper by displacement through
scrap iron or zinc, while the undissolved portion of the mass, consisting of the
oxides of copper, may also be readily reduced to a metallic state in any
furnace prepared for the reduction of copper from its several oxides. In
treating some metalliferous sulphurets, and more especially bisulphurets, prin-
cipally or simply for sulphuric acid, it will be found expedient to dilute the
sulphuret with fine talc, which will augment their ignition, and hasten their
oxidation.
My claims refer to the use of nitrate of soda in the dry process of resolving
and assaying the various metalliferous sulphurets as specified, to the production
of sulphate of copper and its oxides from its various sulphurets, by the use of
the nitrate of soda, as specified, to the manufacture of sulphuric acid by
means of the nitrate of soda mixed directly with metalliferous sulphurets, as
specified.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Homer Holland in the Great Seal Patent Office on the
16th November 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HOMER
HOLLAND, of Westfield, in the County of Hampden, and State of Massachusetts,
in the United States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of May, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,

page_text: the said Homer Holland, Her special license that I, the said Homer Holland,
my exccutors, administrators, and assigns, or such others as I, the said
Homer Holland, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE METHOD OF TREATING METALLIPEROUS SULPHURETS," upon the condition
(amongst others) that I, the said Homer Holland, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Homer Holland, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement (that is to say):-
The chemical re-agent used in my method of treating metalliferous sul→
phurets is the nitrate of soda, an article, I believe, not hitherto employed in
any process of dry assaying, and one of which I have found no mention in any
work or treatise on metallurgy.
The nitrate of potash, which in its general chemical character somewhat
resembles the nitrate of soda, has heretofore been used in a single crystal for
blowpipe testing, and to scorify and oxidize in remelting gold and silver in the
crucible; but it is utterly impracticable in any hitherto recognized process.
for separating gold and silver from the sulphides on a large scale, since it
readily ignites, and its combustion is so violent and explosive as to eject the
mixture from the crucible, while the heat that it generates is so intense as to
volatilize a portion of the metals subjected to its influence, and indeed the use
of the nitrate of potassa, even in dry assaying, is now, according to the best
authorities, obsolete. But, on the other hand, I have discovered and am able
to make use of certain properties in the nitrate of soda which render it highly
useful in the disintegration and resolution of metalliferous sulphides, -and
which shew that it is very different in its action from the nitrate of potash.
Unlike the last-mentioned salt, the nitrate of soda when ignited burns slowly
and mildly, and more especially so with the metalliferous sulphides, while there
is neither violent action to explode or scatter the mixture, nor heat generated
sufficiently intense to volatilize the metals.

page_text: This bitherto unrecognized difference in the action of the nitrate of potash
and the nitrate of soda on metalliferous sulphurets is the property which I
make use of in my Invention, and which I believe to be clearly distinguishable
from all processes hitherto adopted; for although it consists in part of so well
known a material as the nitrate of soda, yet this material is so combined with
and proportioned to the ores acted upon by the methods pursued in my process
as to give the practical chemist and metallurgist advantages essentially different
from those he can obtain from any methods practised in obtaining acid from
any and all sulphides in oxidizing, desulphurizing, and rendering the ores
friable, soluble, or inert, and reducing silver and gold when combined in a
metallic state, and the silver of argentiferous lead soluble; in short, a more
feasible and exact dry assay or resolution for the precious metals.
:
The manner in which my process is conducted is as follows:-A quantity of
the nitrate of soda, as free as possible from any admixture with other salts,
is provided, together with a quantity of any metalliferous sulphide, both being
finely pulverized, jointly or separately, by means of any mechanical contrivance,
in a dry state, the mixing being thorough, the proportions of the nitrate of
soda being adjusted to the sulphur of the ore, one hundred pounds of sulphur
requiring two hundred and ninety-one pounds of oxygen from the nitrate
of soda. About one-third of this mixture must then be deflagrated in a large
cast-iron basin, having a concave sole or hearth, like that of a clausthal cupel,
heated from beneath to moderate redness, and at separate intervals of about
half an hour each the remaining two-thirds are to be added, while the mass in
the basin is being thoroughly stirred and intermixed; or when considerable
quantities are treated, a large iron plate, heated also from beneath, may be used
by deflagrating upon it such portion of the mixture as will cover the plate to
the depth of one inch or more. As soon as this portion is deflagrated it should
be broken up, so as to allow a more free escape of the acids and penetration of
the atmosphere. The basin or plate, however, are to be so placed over the
furnace or fire as to allow the sulphurous, sulphuric, and nitrous oxido and
acid fumes to pass or be blown through a condenser, or passed with steam into
a sulphuric acid chamber, and for this purpose must be surrounded with a
copper or iron box, or ulembic and blower. Then the heat, which is only.
moderate previously to deflagration, must be maintained as long as it is desi-
rable, to expel the sulphuric acid and collect and save it. The sulphide will be
promptly resolved and fully oxidized and made very soft and friable, and after
the deflagrated mass is cooled and lixiviated to remove the soluble sulphates in
copper, iron, and others by water, and in argentiferous galena by sulphuric
acid, which in the first instance removes all the sulphate of copper and soda,

page_text: and in the second place all the silver; the inert compounds remaining allow of
the complete amalgamation of the gold alone, or the gold and silver combined
in their usual natural alloy, and even the gold occurring in auriferous lead, as
from any other fine sands and oxides.
In some instances, however, and more especially in treating the bisulphides,
it will be found expedient to subject the pulverized ore to a preliminary
roasting in order to expel in an acid form some portion of the sulphur, by
which means a certain amount of the nitrato of soda will be saved in the
resolution; and consequently I cannot and do not in any way restrict myself
to any precise ratio of the proportions of the several ores and nitrate of soda;
since a greater or less proportion of the salt will, under different circumstances,
to a certain extent effect the decomposition required.
An excess of the nitrate of soda can in no instance whatever either injure the
process or vitiate the result, nor can likewise the degree of transmitted heat,
provided always it be moderate at first and increased gradually; neither is it
absolutely necessary that in all cases the nitrate of soda should be mixed
before roasting with the ore, since in some instances it may be found advan-
tageous to gradually stir it in while the orc is being roasted. When the
sulphurets are very closely concentrated, they may be diluted with fino talc,
which will augment ignition and hasten their resolution.
When copper
pyrites is decomposed and resolved by my process, the cooled mass must be
lixiviated with hot water so as to entirely remove the soluble sulphate of soda
and copper, as the latter will otherwise waste the mercury in amalgama-
tion. From this mixed solution the copper may be galvanically displaced
by scrap iron or zinc, or concentrated and crystallized out with the soda and
afterwards separated, while the undissolved portion of the mass, consisting
of oxides of iron and silex and suboxide of copper, may be readily reduced to
a metallic state in any furnace prepared for the reduction of copper from its
several ores and oxides.
.
Having now described and particularly set forth the nature of my Invention,
and the manner in which the same is or may be used or carried into effect,
I would observe, in conclusion, that I do not confine myself to the precise
détails or arrangements which I have had occasion to describe or refer to, as
many variations may be made therefrom without deviating from the principles
or main features of my Invention; but what I consider to be novel and original,
and therefore claim as my Invention and device, is,-
First, the use of the nitrate of soda in the dry process of resolving and
assaying the several and various metalliferous sulphides after the manner
herein-before described and indicated.

page_text: Second, the transformation of the auriferous and argentiferous leads or ores
known as galena, into soluble and insoluble sulphates of silver and lead by the
use of nitrate of soda according to the process already set forth, and thus
extracting both its gold and silver.
Third, the production of the sulphate of copper and its oxides from its
various sulphides by the use of the nitrate of soda, as set forth.
Fourth, the manufacture of sulphuric acid from the several and various
metalliferous sulphides on which I may have occasion to operate for their
other valuable products, as set forth, by the nitrate of soda, or for sulphuric
acid singly and directly, by the commingling and deflagration of the ore and
salt, in the manner herein-before described.
In witness whereof, I, the said Homer Holland, have hereunto set my
hand and seal, this Twenty-sixth day of October, in the year of our
Lord One thousand eight hundred and fifty-five.
Witnesses,
HENRY HOLLAND,
Westfield, Mass.
WILLIAM HOLLAND,
Westfield, Mass.
HOMER HOLLAND. (L.s.)