or from Crude Minerals.
Year: 1887

page_text: Date of Application, 15th Apr., 1887.
Specification Accepted, 19th July, 1887..
or from Crude Minerals.
I, AMOS LEFEVRE KEEPORT, residing at Littlestown, in the County of Adams, and
State of Pennsylvania, one of the United States of America, Chemist, do hereby
declare the nature of this invention and in what manner the same is to be
performed be particularly described and ascertained in and by the following
statement:
This invention relates to the art of separating metals from their ores or from crude
minerals and although generally applicable is designed more particularly to the
treatment of ores containing precious metals and especially those metals which have
heretofore been obtained in comparatively limited quantities or only as products of
the laboratory such for instance as the metals of the platinum group.
The invention has for its object the production of these metals for genèral
commercial purposes and at a very low cost as compared with the present market
value thereof. In the extraction of metals from their ores or from crude minerals by
the wet or chemical processes, the operations were exclusively directed to the removal
of the metal sought by means of an agent acting directly upon such metal and this
agent was invariably so chosen as to leave unaffected as many of the other
constituents of the ore as possible, the object being in all cases to separate the
metal at once or directly from the ore and to leave all undesirable matter behind.
This treatment may operate satisfactorily in all cases where the metal sought is not
in a state of great diffusion throughout the ore and in intimate molecular combination
with the other constituents thereof. Even in such cases I have found that a
comparatively large percentum of the metal sought can not be obtained owing to the
intimate molecular combination with substances that are not affected by the reducing
agent of the metal and that effectually protect the latter against its action.
When however ores are treated in which the metal sought is in a state of great
liffusion and in a correspondingly intimate combination with other undesirable
constituents of the ore not affected by the reducing agent employed as is more
especially the case in ores containing the metals of the platinum group, such metals

page_text: are either not reached by the reducing agent or but a comparatively small proportion
of said metals are affected and to this I attribute the failure of obtaining these metals
from ores otherwise rich in such metals and from obtaining them on a commercial
scale.
My invention is based upon principles that are diametrically the reverse of those
upon which the common practice is based. I have discovered that in order to unlock
the metals more effectually from the constituents with which they are so intimately
combined it is necessary to first reduce these constituents to such a state that they will
part with the metal or metals they hold locked up in order to bring such metal or
metals to a condition to be reached by the reducing agent. Hence instead of
proceeding to separate the metal from the undesirable constituents of the ore this
invention aims essentially and primarily at the reduction of the undesirable
constituents of the ore from the metal or metals therein.
Although heretofore never thought of yet this process can not but strike those
conversant with this branch of the arts as the most rational, since by the reduction of
the undesirable constituents the metals will be effectually separated therefrom.
In my experiments with a great variety of ores I have also found that whenever
zirconium was present in the ore other precious metals present would either not be
recovered from the ore at all or only in inappreciable quantities and that whenever this
metal could be removed all other metals became available and could be recovered by
the ordinary chemical processes. The great difficulty I encountered was in the
separation of the zirconium for which all known chemical processes were unavailable.
This led me to reverse the ordinary methods employed in the treatment of ores and
to direct my attention to the removal first of every thing undesirable therefrom that
could be removed and leave the metal or metals sought behind and this has led to
invariable success.
I have since satisfied myself that zirconium was more widely diffused throughout
the minerals than has ever been thought possible, in fact I have found but few ores in
which this metal was not present in a greater or less proportion and so far as my
experience has gone is generally present in ores that contain iron, aluminium and
magnesium.
I have since discovered also, that zirconium has a greater affinity for the precious
metals of the platinum group than any other metal of that group or in fact than any
other metal with which I am acquainted, and it has that characteristic feature as to
gold which is locked up thereby in almost incredible proportions. I became satisfied
as to this in the treatment by my process with a view to obtaining gold of ores that
after a careful analysis, or assaying were declared alsolutely worthless as regards any
precious metals and from which I have obtained gold in paying quantities.
I may therefore state that my process comprises a first essential step and that is in
treating the ore in such a manner as to eliminate therefrom as many as possible of
the undesirable prevalent constituents by means of an agent or agents that will leave the
metal or metals sought unaffected. A second essential step and that is to reduce the
zirconium if any be present in the ore to a condition in which it may be separated
without affecting the other metal or metals sought so as to leave them in a state of
separation in which they may be obtained by the ordinary chemical processes.
The reducing agent should therefore be so chosen as to act upon a majority of the
undesirable and most prevalent constituents of the ore treated without affecting the
metal or metals sought or if affected to have a different or distinctive action upon
them as a secondary result of the operation an absolute disintegration of the ore must
necessarily follow leaving the unaffected or the differently affected metal or metals in
a condition of perfect separation for recovery by those processes which have hitherto
been employed ab initio.
It follows from the above that the perfect reduction or disintegration of an ore
depends essentially upon the proportion of matter directly affected by the primary
reducing agent. Hence if this agent is chosen with a view to act directly upon a majority
of the undesirable prevalent constituents of the ore leaving the desirable constituents
unaffected or affected in a different manner the desired result is obtained. For

page_text: instance if an ore containing three, four or more of the metals of the platinum group
combined with aluminium, iron, magnesium &c. and silica is to be treated for the
recovery the metals of said platinum group instead of resorting to those reagent-
that will ab initio act directly as 'a solvent for example upon one or more of the metals;
I on the contrary determine first the nature of the ruling elements of the ore and
then select a reducing agent that will reduce a majority of these elements and will
leave the remainder unaffected. This reduction of the ruling or prevalent undesirable
. elements of the ore results in a complete disintegration and the separation therefrom
of the metals.
The primary reducing agent may under some conditions also affect one of the
metals sought but in such a case it should be so chosen that its action upon such metal
shall be different from its action on the prevalent constituents. For instance if the
primary reducing agent acts as a solvent upon the prevalent undesirable constituents
of the ore it should have an oxydizing or chloridizing action upon such metal in which
case we obtain; First a solution of all the constituents of the ore soluble in the primary
solvent Second the reduction to an oxide or a chloride of the metals susceptible to
this reduction by the action of the primary solvent and third, the metals and silica &c.
not affected by the solvent.
In view of the great difference in the specific gravity of the products of the reaction
and the insolubles they may be readily separated from one another leaving the metals
sought in a condition for recovery by the ordinary processes. The primary reducing
agent may also have an oxydizing action upon an undesirable metal in the ore or may
act to reduce such metal to a chloride in which case the supernatant solution together
with the oxide or chloride can be separated from the silica and the other metals not
affected by the reducing agent.
But that my invention may be fully understood I will describe the same in detail in
its application to the treatment of ores containing the metals of the platinum group,
the ore being supposed to be composed of silicates, iron, magnesium aluminium &c. as
the ruling or prevalent constituents and of zirconium, palladium platinum and osmium.
The primary reducing agent in this case will be hydrochloric acid since a majority
of the prevalent undesirable constituents of the ore are soluble in said acid which also
acts as an oxydizing agent upon zirconium. The ore is pulverized and four parts of
hydrochloric acid is added and allowed to digest from four to six days, stirring it
occasionally.
I would here state that the reaction is accelerated in proportion to the degree of
comminution of the ore within certain limits and its nearing completion may be
ascertained from the formation of a stratum of zirconia above the stratum of silica
and the metals not affected by the acid after stirring the ore and letting it settle.
This is simply the result of the difference in the specific gravities of the solution, the
insolubles and the zirconia.
This separation of the oxide may be perfected by imparting to the vessel such a
motion as will only slightly agitate the insolubles the zirconia rising to the surface
thereof and depositing thereon. In this manner a perfect disintegration of the ore is
effected and the products of the process are now in a condition for treatment by the
processes heretofore employed, the metals being obtained in their regular and usual
order namely :-
First, Zirconia; The supernatant solution of the prevalent constituents in the ore
is decanted from the insolubles together with the zirconia and the latter is allowed
to settle.
The solution is then decanted or the zirconia eliminated therefrom by filtration. To
the zirconia is then added two parts sulphuric acid and one half as much water and the
whole subjected to heat (boiled) until the zirconia precipitates.
The acid is then
decanted and the zirconia filtered out and evaporated to dryness. The product being
a hydroxide of zirconium perfectly white.
Instead of proceeding as above the solution of iron &c. may be decanted from the
zirconia and the insolubles from which latter the zirconia is removed by elutriation
allowed to settle and after filtration or decantation treated with sulphuric acid &c.

page_text: In either case a residue of insolubles is obtained that is composed of the silicates and
the other metals which when the zirconia is decanted with the solution of the
prevalent soluble constituents of the ore is washed to remove any zirconia left behind
after decantation as well as any sulphates chlorides &c. of iron, aluminium,
magnesium &c. that may have formed during the reaction, these being soluble in
water.
When the supernatant solution is decanted without the zirconia and the latter
separated from the insolubles by elutriation the remaining insolubles need not be
further washed since the soluble sulphates &c. are then eliminated with the zirconia.
The zirconia when evaporated to dryness presents the following characteristics. It is
non-magnetic and when exposed to a gentle heat it turns to a pronounced yellow
becoming white again on cooling but when exposed to a high degree of heat i.e. when
ignited it becomes reddish brown and at the same time becomes magnetic.
Second. Palladium. The insolubles are now treated with aqua regia cold, or with
nitric acid and heat for from six to twenty four hours or until the solution shows a
good degree of saturation which may be ascertained from its yellowish color. The
solution is then decanted from the remaining insolubles and evaporated to dryness.
The product if subjected to a sufficiently high temperature will result in palladium
sponge, if on the contrary the solution is treated with potassium iodide black palladium
iodide is precipitated which is very characteristic. If mercuric cyanide is employed the
precipitate will be palladium cyanide yellowish white soluble in ammonium sulphide
and also very characteristic.
Third. Platinum. The insolubles left after the separation of the palladium there-
from are now treated with aqua regia and heat stirring occasionally so as to dissolve
out all the platinum leaving behind most of the osmium. After standing some hours
the platinum solution is decanted or filtered off and one half part hydrochloric acid is
added and then sufficient ammonia (NH3) to precipitate the platinum, about three
parts ammonia will suffice. This precipitate obtained is generally yellow, but some-
times reddish yellow and more or less crystalline and is a trichloride of ammonium,
platinum and osmium not precipitated by sal ammoniac alone.
When ignited or heated to a red heat a dull gray platinum sponge is obtained.
The platinum black may be obtained from the solution by the ordinary methods. I
would here state that the palladium solution is readily distinguishable from the
platinum solution the former being yellowish while the platinum solution is darker
tending to brown.
Fourth. Osmium. A portion of the osmium is obtained together with the platinum
by the means above described and can be separated by ignition and sublimation of the
osmium tetroxide which is white and at a greater distance from the heat than the
tetrachloride which is red, the separation being effected according to their color while
the platinum is obtained at the source of heat in the form of sponge. Care should here
be had that none of the ammonium chloride is sublimed with the osmium tetroxide.
In the reduction of the platinum to sponge by heat the osmium chloride is first
volatilized and if the vapors are brought into a flame show distinctive iridescence in
combustion the ammonium chloride is next volatilized and may be readily dis-
tinguished by the denser and greater volume of fumes and the sponge is sometimes of
a dull dark gray color and sometimes of a dark brown color according to the degree
of heat applied. The remaining silica is now treated with aqua regia and heat until
it yields no more osmium the greater portion of which is obtained from the last
decantings.
I have also discovered that after the insolubles have been apparently exhausted
there remains a considerable portion of white osmium tetroxide which can be obtained
from the insolubles by elutriation and then dried at a gentle heat, care being had in
the latter separation that none of the remaining silica is carried over with the osmium
tetroxide.
The osmium solution is treated with hydrochloric acid in the proportion of about
one half part and sufficient ammonia to precipitate the osmium which is obtained in
the form of a tetroxide which is then dried at a gentle heat. The black metallic

page_text: Osmium may readily be obtained by the ignition of the precipitate with sal ammoniac.
The gray osmic oxide may be obtained by igniting some of the precipitate with sodium
carbonate a friable grayish oxide being the result.
I have discovered that if the solution obtained by the action of a primary reducing
agent upon the one is employed as a primary reducing agent in further operations
that the reactions take place more rapidly and powerfully and a better separation is
obtained. To this end I add to the solution about one fourth of the primary reducing
agent at each fresh operation and use the same until too highly charged with one or
more of the undesirable constituents of the ore.
In the case above referred to the solution would after repeated use become so highly
charged with iron as to be of no further use and it is then discarded or so much
hydrochloric acid may be added as to reduce the percentum of iron to the desired
point. I have hereinabove described a continuous process for separating a plurality
of metals from an ore it will however be readily understood that the process is
available in the separation of a single metal this depending upon the quantitative
preliminary analysis of the ore as to whether a plurality of metals are present in such
proportions as to render it advisable to obtain them all the process in its essential
feature remaining the same the variations being those inherent to the final separation
of the metal or metals. Thus if in the above case zirconia were the objective product
the process would terminate with the separation of the zirconium oxide and its
conversion into a hydroxide.
If on the contrary palladium were the objective product the process would terminate
with the separation of the palladium solution and the conversion of the palladium into
the product desired sponge, black iodide &c. and so on for the remaining metals.
In my experiments upon variously constitutes ores I have also found that the
separation takes place more perfectly more regularly and more rapidly when zirconium
is present in the ore and in the treatment of ores in which zirconium is not present, I
prefer to add an ore containing zirconium to the ore treated or add zirconium oxide
to the primary reducing agent.
I am unable to positively indicate the action of the zirconium or the zirconia upon
the ore or upon precious metals or upon metals of the platinum group except
theoretically and I think this action is due to the great affinity of the zirconium or
the zirconia for said metals and tends to unlock the same.
For the purposes of illustrating the invention the example hereinabove may suffice
but in order to shew that the process is applicable to all ores or minerals for the
recovery therefrom of precious metals and in order not to lengthen this description
unnecessarily I will give one more example shewing the operation of the process on a
supposed auriferous ore from Colorado.
The ruling metals in this ore I found to be lead and silver and selected the primary
reducing agent accordingly and treated the pulverized ore with nitric acid (H N O₂) to
dissolve the lead and silver. For reasons hereinabove stated I next operated upon the
residues with a view to ascertaining whether zirconium was present in order to
remove the same and unlock the gold or if not present to add a zirconium ore or
zirconia; I found zirconia (Z ROH2) to be present and concluded that other metals
of the platinum group were present and operated accordingly and as hereinabove
described. The result of the operation briefly stated is as follows:-
Chloride of silver,-large; Plumbic hydrate,-large; Gold, small; Zirconia, small;
Palladium iodide, considerable; platinum (yield in sponge) large; Osmium and
iridium, traces; and insoluble silica &c., large.
The application of the process to this ore unquestionably proved that the paying
metals was not gold but that the ore contained three metals that could profitably be
extracted therefrom, namely, silver, palladium and platinum.
I would state that this ore had been reported as worthless by several assayers.
Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed I declare that what I claim is :-
First The process of separating metals from their ores or from crude minerals

page_text: which consists in subjecting the same to the action of a reducing agent acting
essentially upon those constituents of the ore that hold the metal or metals to be
separated locked up to release the same in contradistinction to the ordinary method of
subjecting the ore to the action of a reducing agent acting directly upon the metal or
metals to be separated without essentially affecting the other constituents of the ore,
substantially as described for the purposes specified.
Second-The process of separating metals from their ores or from crude minerals
which consists in subjecting the same to the action of a solvent the nature of which is
determined by the constituents of the ore that are soluble therein and in which the
metal or metals to be obtained are insoluble, separating the solution of said soluble
constituents from the insoluble and separating the metal or metals from the latter by
the ordinary processes of chemistry, substantially as described.
3. In the separation of metals from their ores a primary reducing agent or solvent
holding in solution the soluble constituents of the ore to be treated or the most
prevalent soluble constituents thereof and in which the metal or metals to be obtained
are insoluble, substantially as and for the purpose specified.
4. The process of separating the metals of the platinum group from their ores which
consists in subjecting the ore to the action of a solvent in which the metal or metals
to be obtained, remain insoluble and that will act as an oxydizing agent upon
zirconium if present in the ore, dissolving out all the soluble constituents, separating
the constituents in solution from the metals or the metals and oxide of zirconium and
other insoluble constituents separating the oxide from the remaining metals and
insolubles, and finally separating the metals from said insolubles by the ordinary
methods of chemistry, substantially as described.
5. The process of separating the metals of the platinum group from their ores,
which consists in subjecting the ore to the action of a solvent, holding in solution the
soluble constituents or the most prevalent soluble constituents in the ore, and incapable
of dissolving the metal or metals to be obtained, and acting as an oxydizing agent
upon the zirconium if present in the ore, dissolving out all the soluble constituents,
separating the constituents in solution from the metals or the metals and oxide of
zirconium and other insoluble constituents separating the oxide from the remaining
metals and insolubles and finally separating the metals from said insolubles by the
ordinary methods of chemistry, substantially as described.
6. The process of separating the metals of the platinum group from their ores,
which consists in subjecting the same to the action of a solvent in which the metal or
metals are insoluble and that will act as an oxydizing agent upon zirconium, adding
zircon to the ore or zirconia to the solvent if the ore treated is deficient in zirconium,
dissolving out all the soluble constituents, separating the constituents in solution from
the metals or the metals and oxide of zirconium and other insoluble constituents
separating the oxide from the remaining metals and insolubles and finally separating
the metals from said insolubles by the ordinary methods of chemistry substantially as
described.