IMPROVEMENTS IN EXTRACTING AND SEPARATING GOLD AND SILVER FROM THEIR ORES OR MATRICES, AND IN THE TREATMENT OF MERCURY EMPLOYED FOR SUCH *PURPOSES
Year: 1865

page_text: LETTERS PATENT to William Crookes, F.R.S., of Wine Office Court,
L...
Fleet Street, in the City of London, for the Invention of "IMPROVEMENTS
IN EXTRACTING AND SEPARATING GOLD AND SILVER FROM THEIR ORES OR
MATRICES, AND IN THE TREATMENT OF MERCURY EMPLOYED FOR SUCH
*PURPOSES."
Sealed the 23rd February 1866, and dated the 30th August 1865.
PROVISIONAL SPECIFICATION left by the said William Crookes at the
Office of the Commissioners of Patents, with his Petition, on the
30th August 1865.
I, WILLIAM CROOKES, F.R.S., of Wine Office Court, Fleet Street, in the
5 City of London, do hereby declare the nature of the said Invention for "Ix-
PROVEMENTS IN, EXTRACTING AND SEPARATING GOLD AND SILVER PROM THEIR ORES
OR MATRICES, AND IN THE TREATMENT OF MERCURY EMPLOYED FOR SUCH PURPOSES,"
to be as follows:..
This Invention relates to certain improvements in the method of treating
0 ores or substances containing gold and silver by amalgamation, and also in
the treatment of mercury employed in such operations.
It is well known that the extraction and separation of gold and silver by
the process of amalgamation from the substances with which they are com-

page_text: bined is much impeded or rendered costly by the mercury employed becoming
converted into sulphide, chloride, sulphate, or other compounds, or divided
into minute globules, technically known as "flouring" or "powdering," and
also by its heing partially deprived of its fluidity, technically termed
"sickening," and thereby losing its power of adhering to or taking up the
precious metal under treatment.
A partial remedy for these evils has been provided by an Invention for
which Letters Patent have been granted to me, bearing date the Eleventh
day of February, One thousand eight hundred and sixty-five, and numbered
391, and which mainly consists in the addition of sodium, either in the form
of an amalgam, or in the pure metallic state, to the mercury employed for
the purposes of amalgamation.
The present Invention consists in the addition to the mercury used for
amalgamation of certain metallic substances, that is to say, iron, zinc, tin,
and cadmium, either separately or in combination, and either in the form of
an amalgam with mercury, or as regards zinc, tin, and cadmium directly in
the pure metallic state; or instead of so combining those metals, or any or
either of them, with the mercury in the first instance they can be reduced
electro-chemically from compounds, so as to unite with mercury in the act of
separating; or ores of or compounds containing the same may be mixed with
the ores or substances containing the precious metal, and the whole ground
together and submitted to the action of mercury in which a metal has been
dissolved or reduced, which is capable of reducing to the metallic state the
metal which it is desired so to introduce, in order to assist and facilitate the
In either of these
process of extracting and separating the precious metal.
modes of combining the before-mentioned metals, or any or either of them
with the mercury used for amalgamation, the result will be to protect the
mercury from chemical action, and also to prevent the " flouring" or
"powdering" or " sickening" of the latter, and to increase its tendency to
unite together into large globules.
In order to facilitate the separation of gold and silver from the substances
containing those metals, or with which they are mixed, when the surfaces of
the precious metal are in a tarnished or soiled state, as where gold or silver
occurs with pyrites, sulphurets, chlorides, or minerals containing arsenic,
antimony, tellurium, or bismuth, it is advisable to introduce sodium into the
mercury in accordance with my said former Invention, together with one or
more of the above-mentioned metals, and in all cases such metals, or any or
either of them, may with advantage be used for the purposes of amalgamation
in combination with sodium, as employed in my said former Invention.. .In

page_text: cases also in which a great excess of sodium has been used in working my
former process, the evils consequent thereon can be remedied by combining
one or more of the before-mentioned metals with the mercury in addition to:
the sodium. In the amalgamation of gold the bright metallic condition
of the mercury may be maintained or restored by the addition thereto of a
small quantity of cyanide of potassium during the operation of grinding.
I am aware that iron in the solid metallic state has already been employed.
in the process of silver amalgamation, but its action in this form is different
from what it. is when added in the form of an amalgam with mercury,
either with or without any of the other metals herein-before mentioned. I
may also mention that in silver amalgamation the action of the metals in the
mercury is principally chemical, whilst in gold amalgamation, the zinc,.
cadmium, and other metals appear to act more mechanically and physically
than in the former case. It may be here mentioned that although iron, zinc,
tin, and cadmium have been herein-before mentioned as applicable to the
purposes of this Invention, yet barium, strontium, calcium, magnesium,.
aluminium; manganese, copper, lead, thallium, cobalt, and nickel may also be.
employed with like results, although the price or physical or chemical
properties of the last-mentioned metals renders them at present practically
unavailable for use. on a large and commercial scale. With regard to the
proportions in which the aforesaid metals should be combined with the
mercury, or with each other, it is impossible to fix any precise limits, as
the operator must be guided by his skill and experience, and the condition of.
the substances containing the precious metals under treatment.
A.further mode of treating mercury with the object of rendering it better
fitted for the purposes of amalgamation during the process of trituration is
effected either by placing the mercury in connection with the zine or negative
pole of an electrical battery, or to subject it to such chemical agencies as will-
be calculated to liberate nascent hydrogen on its surface by the decomposition
of the liquid employed.
ATION pursuance of the conditions or the Letters Patent, filed
by the said William Crookes in the Great Seal Patent Office on thé
28th February 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
5 CROOKES, F.R.S., of Wine Office Court, Fleet Street, in the City of London,
send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of August, in the year of our Lord One
thousand eight hundred and sixty-five, in the twenty-ninth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
William Crookes, Her special licence that I, the said William Crookes, my
executors, administrators, and assigns, or such others as I, the said William
Crookes, 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 EXTRACTING, AND.
SEPARATING GOLD AND SILVER FROM THEIR 'ORES OR MATRICES, AND IN THE TREAT-
MENT OF MERCURY EMPLOYED FOR SUCH PURPOSES," upon the condition (amongst
others) that I, the said William Crookes, my executors or administrators,
by an instrument in writing under my, or their, or one of their hands and seals,
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 William Crookes, do hereby declare
the nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement (that is to say) :-
:-
My said Invention relates to certain improvements in the method of
treating ores or substances containing gold and silver by amalgamation, and
also in the treatment of mercury employed in such operations.
In order. that my said Invention may be clearly understood, I will in the
first place refer to its application to the treatment of silver ores, and then to
its use in the treatment of gold ores or substances containing gold.
SILVER ORES.
1. Silver occurs native, or in combination with gold, mercury, and other
metals; also as chloride, bromide, iodide, sulphide, and with compounds
containing antimony, lead, iron, copper, and other elements. From some of
these compounds the silver is extracted by amalgamation with mercury, whilst
from others it is extracted by smelting or by other means.
The processes herein described are only applicable to the amalgamation
method.
The chief, causes of loss in silver amalgamation are, a, the flouring" or

page_text: powdering of the mercury, owing to the mechanical treatment it undergoes;
b, the "sickening" of the mercury, 'owing to the presence in the ore of iron
pyrites and certain minerals containing bismuth, antimony, arsenic, sulphur,
tellurium, and other elements; c, the chemical change of the mercury into
corrosive sublimate, calomel, and other similar compounds, which takes place
whilst in the act of reducing chloride of silver (or similar compounds) to the
metallic state. By far the greater quantity of mercury is lost in this last
manner. According to Dr. William Allen Miller, F.R.S., the loss of mercury
from this cause alone has, in South America, amounted to three hundred thousand
tons, representing a money value of about eighty million pounds sterling.
2. The process about to be described will be found to be a remedy for each
of the above-named evils. The flouring" a and "sickening" 6 of the
mercury are by its means effectually remedied. These conditions being com-
mon to both silver and gold amalgamation will be more especially referred to
under the heading of "Gold Ores;" but the cause of loss c belongs more
peculiarly to silver amalgamation, and is therefore more appropriately discussed
here.
8. For the sake of illustrating the subject more clearly, most of the
complicated reactions which take place during silver amalgamation may be
disregarded, and attention only directed to the following points :-When
chloride of silver and metallic mercury are allowed to remain in contact under
the circumstances in which they are mingled together at a silver amalgama,
tion works, an exchange of elements gradually takes place, the chlorine
leaving the silver and going over to the mercury, the result being metallic
silver and chloride of mercury, whilst the metallic silver, at the moment of
separation, unites with a fresh quantity of metallic mercury and forms silver
amalgam. An endeavour is sometimes made to save the mercury by adding
metallic iron to the mixture, by means of which, theoretically, chloride of iron
would-be produced, and metallic mercury obtained; but in practice this result
is only imperfectly effected, as in the first place, the greater portion of the
chloride of mercury exists in the form of calomel, which is with great difficulty,
or not at all, reduced by iron; and in the second place the mercury, when it
is brought back to the metallic state by the action of iron, is chiefly in the
form of a black or grey powder or "flour," which will scarcely collect into the
bright liquid state, but is washed away and lost with the earthy matters.
4. By dissolving in the mercury, or mixing with it, some of the amalgam B,.
herein-after described, in the proportion of two parts of the amalgam for every
one part of silver present in the ore which is about to be treated, these evils
are prevented. For instance, if a certain portion of silver ore contained one

page_text: pound weight of silver, and it had been decided to employ for the purpose of
extracting this silver a certain weight of mercury, I should recommend the
addition of two pounds weight of amalgam B to the mercury before it is
mixed with the silver ore. The chlorine then goes to the other metals present
instead of to the mercury, and the decomposition takes place so rapidly that
an operation which formerly would take a week is sometimes completed in
twelve hours.
5. With care in manipulation and a few preliminary essays to ascertain the
best proportion of amalgam B to add to the mercury, none of the latter need be
lost. The saving thus effected is very great, for it must be remembered that
for each pound of silver, worth, say sixty shillings, nearly two pounds of
mercury, worth, say five shillings, are frequently wasted. By the new process
this money loss is reduced to a few pence.
6. When the mercury is brought to the state of "flour" (as in the reduc÷
tion of the chloride by metallic iron spoken of above) and difficulty is found
in getting this powder into the bright liquid state, a little of amalgam A
(herein-after described) rubbed along with it under water will quickly render
a. When certain sulphurets or compounds of arsenic, antimony, bismuth, tellu-
rium, or other elements are present along with the gold (and especially if the
latter occurs in "pyrites") the mercury in which the mineral is triturated, or
ground becomes "floured" or powdered, i.e. it becomes subdivided into
excessively minute globules, which, owing to the film of tarnish they have
contracted refuse to unite and are consequently washed away, as it is almost
impossible to effect their separation from the heavier portions of ore by any
known process of washing in water. b. The presence of some of the above-
mentioned minerals affects the mercury in another way, viz., by "sickening"
it. I believe the "sickening" and "flouring" are frequently due to the
same cause, the former being the preliminary stage to the latter. "Sick "
mercury has lost its fluidity, and will not flow with a bright surface,
neither will it touch gold except with great difficulty. The ill effects of
"sickening" are not so great as those of "flouring," for "sick" mercury can
generally be restored by distillation, in which case there is not much loss,
the chief objection being that it will not take up gold from the ore; but
"Aloured" mercury is not only entirely lost, but it carries away with it all the gold
which it may already have taken up. c. Another very serious cause of loss is

page_text: this, even when the mercury preserves its bright metallic condition, and is in
the most active state ever met with in commerce, it will. seldom take up more
than half or two-thirds of the gold present in the ore, owing to the precious
metals being naturally tarnished on its surface, and resisting the action of the
mercury, except when they are ground together for a longer time than is
usually practicable.
8. A partial remedy for these evils has been provided by an Invention for
which Letters Patent have been granted to me, bearing date the Eleventh
day of February, One thousand eight hundred and sixty-five, and numbered
391, and which Invention mainly consists in the addition of sodium, either
in the form of an amalgam, or in the pure metallic state, to the mercury
employed for the purpose of amalgamation.
The present Invention consists in the addition of certain other metallic
substances to the mercury used for amalgamation, that is to say, zinc and tin
either separately or in combination, and either in the form of an amalgam
with mercury, or directly in the pure metallic state; or instead of so com-
bining those metals or either of them with the mercury in the first instance,
they can be reduced electro-chemically from compounds so as to unite with
mercury in the act of separating; or ores of or compounds containing the same
may be united with the ores or substances containing the precious metal, aud
the whole ground together and submitted to the. action of mercury, in which a
metal has been dissolved or reduced, which is capable of reducing to the
bright metallic state the metal which it is desired so to introduce in order to
assist and facilitate the process of extracting and separating the precious metal.
9. In either of these modes of combining the before-mentioned metals or
either of them with the mercury used for amalgamation, the result will be to
more or less protect the mercury from chemical action, and also to prevent
the "flouring" or "powdering" or-"-sickening." of the latter, and also to
increase its tendency to unite together into larger globules.
10. In order to facilitate the separation of gold and silver from the sub-
stances containing those metals, or with which they are mixed, when the surfaces
of the precious metals are in a tarnished or soiled or greasy state, as when
they occur with pyrites, sulphurets, chlorides, or minerals containing arsenic,
antimony, tellurium, or bismuth, it is advisable to introduce sodium into the
mercury, in accordance with my said former Invention, together with one or
both of the above-mentioned metals; or either of them may with advantage
be used for the purposes of amalgamation in combination with sodium, as
employed in my said former Invention. In cases also in which a great exces
of sodium has been used in working my former process, the evils consequ. ut

page_text: thereon can be remedied by combining one or both of the before-mentioned
metals with the mercury in addition to the sodium.
11. In practice, I prefer to conduct the operation by preparing an
amalgam of sodium, as described in the Specification of my former Invention,
above referred to, and also further on in this present Specification, and also
other amalgams containing mercury and zinc, or mercury, zinc, and tin, as
herein-after described; these I designate for distinction amalgam A, amalgam B,
and amalgam C.
treatment.
12. I dissolve or mix a little of amalgam B or amalgam C in the mercury
before it is introduced into the amalgamating vessels. With regard to the
best proportions in which the aforesaid metals or amalgams should be
combined with the mercury or with each other, these will have to be found
out by experiment, nearly every different class of ore requiring a different
The operator will have to be guided in some measure by his own
skill and experience, and by the kind, quality, or condition of the ores or
matrices under treatment containing the precious metals. I will give as
copious directions on this point as I possibly can, but must preface them by
saying, that although they are such as I have found to answer best in my own
working, yet considerable latitude may be permitted, and the addition of a
little more or less than the recommended quantities does not appear to do
appreciable barm; I therefore recommend that, at the commencement, one
part of amalgam B or amalgam C be dissolved in thirty parts of the mercury
which is to be used in the gold amalgamating vessels or triturating or grinding
machines, and the effect which it produces on the mercury noted from time
to time during the operation. If the mercury retain its brightness and
activity to the end of the operation, it is a sign that either sufficient, or too
much has been added, and a second experiment should be tried with the
addition of a diminished quantity of amalgam; but if the mercury be
"floured" or "sick," or if any be lost, more amalgam may be added until
the best proportion is arrived at. Amalgam B will generally be found to be
éffective, but if the ore contain an excess of any mineral which has a dele-
terious action on the mercury, more especially if this mineral contain bismuth,
it will be advantageous to employ amalgam C instead of amalgam B.
13. When the best proportion of amalgam B or of amalgam C is found-
out, I advise the occasional introduction of small quantities of amalgam A into
the mercury already containing amalgam B or amalgam C in the proportion
of one part of amalgam A to 1,000 parts of mercury. This quantity of
amalgam A can be added every 3, 6, 12, 18, or 24 hours according to cir-
cumstances, but one charge of amalgam B or amalgam C. will usually be

page_text: sufficient for the mercury for several days or a week. In some circumstances
it may be found advisable to add amalgam B or amalgam C every day or
two, but a little experience and comparison with the results obtained in
previous trials will soon shew how these agents are best utilized. Amalgams
B and C are chiefly of use in preventing the mercury from "sickening".or
"flouring," whilst amalgam A is most powerful in increasing the mutual
affinity between mercury and gold or silver, and in bringing back "sick" or
floured" mercury to the bright liquid state.
.
14. In many gold amalgamating works it is found advantageous to employ
amalgamated surfaces of copper, over which the crushed ore, tailings, slimes,
or such like materials are allowed to flow, or to introduce analgamated copper.
plates into the triturating and grinding machines. By these means some of
the gold and floured" mercury which would have been otherwise lost in the
tailings is collected on the copper, and may be scraped off from time to time..
The adoption of this principle will be found of great use in all gold or silver
amalgamating works, where I recommend the extensive employment of
amalgamated metallic surfaces for the riffle boxer, launders, shaking tables,.
floors, or other parts along or over which the crushed ore, tailings, slimes, or
other like material flow.
15. By employing amalgam A in coarse powder, and sprinkling it over
the wetted metallic surface which it is wished to amalgamate, and then
rubbing it over with a little clean mercury, a firmly adherent and brilliant-
coating of mercury will be given to the metal. Not only can copper be
amalgamated in this manner, but the same result is produced on galvanized:
iron (iron coated with a thin layer of zinc), on tin plate (iron coated with a.
thin layer of tin), lead, and less perfectly, on iron and steel. In. all cases it
is advisable to preserve the effective surface and the amalgamating energy of,
the mercury on the metal by an occasional sprinkling of powdered amalgams A-
applied from time to time as required.
16. A further mode of treating mercury with the object of rendering it
better fitted for the purposes of amalgamation during the process of trituration.
consists in placing it in connection with the ziue or negative pole of a galvanic
battery, or in subjecting it to such chemical or other agencies as will be
calculated to liberate nascent bydrogen on its surface by the decomposition of
the liquid under which it rests.
17. It may also be mentioned, that although zinc and tin have been herein-
before mentioned as applicable to the purposes of this Invention, yet barium,
strontium, calcium, magnesium, aluminium, cadmium, iron, manganese,
copper, lead, thallium, cobalt, and nickel, may also be employed with like

page_text: results, although the price or physical or chemical properties of the last-
mentioned metals renders them at present practically unavailable for use on a
large and commercial scale. The following experiments will shew the special
action of amalgams A, B, and C upon "floured" and "sick" mercury, upon
silver ores and upon gold, native or otherwise.
.
18. Take about five grains of pure mercury and put it into a small dish or
a watch glass, pour over it a few drops of sesqui-chloride of iron; this will
"sicken" the mercury readily, especially if it be moved about with the finger:
When thoroughly "sick" drop into it a piece of amalgam B or C about one-
hundredth part the size of the mercury; the "sick" mercury will instantly
recover and reassume its globular form.
19. "Sicken" another globule of mercury in the same manner, pour on to
it the recovered mercury from the former experiment (18), and it will be
seen to cure the second portion also.
66
20. Thoroughly flour" or powder a dozen grains of mercury by violently
shaking them in a bottle with weak gum water and a few drops of sesqui-
chloride of iron;. pour off the liquid and wash the residue once or twice; now
transfer the powdered mercury to a plate or dish, and put into it a grain of
amalgam A, and gently rub them together under water; in a few minutes the
whole of the mercury will be reduced to the bright metallic state.
21. Take two portions (about one hundred grains each) of pure mercury; pour
water over them, and into one part put ten grains of amalgam A; now take
a piece of gold ore containing visible gold, and dip it into the pure mercury;
scarcely any or no action will take place; now dip the same piece into the
amalgamated mercury, and the latter will instantly unite with the gold and
whiten it. A gold coin dipped into common mercury will seldom be acted on
except in a few spots, but when dipped into the amalgamated mercury it is
instantly wetted by the metal over its whole surface. The same experiments
may be performed with a silver coin or a piece of gilt paper.
$6
22. The following experiments will shew that the addition of amalgam B
or amalgam. C to mercury will prevent the latter from "flouring" or
sickening"-Take some iron pyrites, with which may be mixed, if desired,
any of the ores which are most antagonistic to amalgamation by the ordinary
process, such as arsenic or tellurium ores, but if these are not conveniently
obtainable they can be left out. Grind up 100 grains of this mixture with
five grains of pure mercury and a very little water for about two minutes, and
then wash away the pyrites and examine the state of the mercury which is
left behind. Nearly all will be washed away, and what is left will be in the
form of a dull-looking powder or "flour."

page_text: 23. Next repeat the same experiment after having added to the mercury
a small piece of amalgam B or C. The mercury will be kept in the bright
globular condition during the whole of the experiment, and upon washing
away the pyrites, the whole of the metal will be recovered in a few large
globules without any appreciable loss. If the pyrites or added mineral.
contains gold, the amalgamated mercury, will, upon examination, be found to
have taken it nearly all up, whilst the common. mercury will have taken up
scarcely any.
24. The following experiment will shew that the presence of grease, so
fatal to gold or silver amalgamation, as ordinarily conducted, has no deleterious,
influence whatever in this improved process :-Agitate mercury in a bottle
with a few drops of oil, and then transfer the mixture to a small dish; the
mercury will be seen to be thoroughly "sickened" and "floured;" now add.
a small lump of amalgam A and a little water; stir for a few minutes, when.
the mercury will gradually return to its normal condition; now, without
removing the greasy impurities from the surface, immerse some metallic gold.
in the mercury, as described in a former paragraph (21), and it will be
immediately attacked.
25. The following experiment illustrates the efficacy of amalgam B in
reducing silver ores:-Take a lump of dry chloride of silver and put it-in a
watch glass or a small dish; cover it with water, and put a globule of mercury
of about its own bulk in contact with it; the two may be rubbed together for
hours without any apparent change taking place, but if a piece of amalgam B
be dropped into the mercury, the latter will immediately take hold of the
chloride of silver, and in a few minutes will appear to have eaten its way.
through the lump, reducing it in the first place to the metallic state, and then:
amalgamating with the silver.
26. I am aware that iron and other metals in the metallic state have
already been employed in the process of silver amalgamation, but their action
in this case is different from what it is when added in the form of an amalgam
of mercury. I may also state, that in silver amalgamation the action of the
metals in the mercury is principally chemical, whilst in gold amalgamation
the sodium, zinc, and other metals appear to act more mechanically and.
physically than in the former case.
27. I prefer the following methods of preparing the amalgams referred to
in this Specification:-

page_text: 30. Weigh out seventy-seven parts of mercury, three parts of sodium, ten
parts of zinc, and ten parts of tin; proceed exactly as in making amalgam B,
ouly adding the tin to the ziuc in the first instance.
31. Metallic sodium and all amalgams containing it must be carefully
preserved from damp air in well-closed vessels.
Having thus declared the nature of my said Invention, and the manner
in which it is to be performed, I would observe, in conclusion, that what I
consider novel and original, and therefore claim as constituting my said
Invention, are the employment of zinc and tin and such other metals as
herein-before mentioned as being applicable to the purposes of this Invention,
and also of such several processes as aforesaid, for the extraction and

page_text: separation of gold and silver from the ores or substances containing them, and
for the treatment of mercury employed for such purposes, as substantially
herein-before set forth and described.
In witness whereof, I, the said William Crookes, have hereunto set my
hand and seal, this Twenty-sixth day of February, in the year of our
Lord One thousand eight hundred and sixty-six.
Witness,
E. P. H. VAUGHAN,
54, Chancery Lane,
Agent for the Patentee.
WILLIAM CROOKES. (L.s.)