Chlorine from Auriferous Ores, Sand, Residues of Gold- washing, and the like.
Year: 1884

page_text: Chlorine from Auriferous Ores, Sand, Residues of Gold-
washing, and the like.
I, HENRIK MUNKTELL, of Falun, Sweden, Engineer, do hereby declare the
nature of said invention for "IMPROVEMENTS IN THE PROCESS OF EXTRACTING
GOLD BY MEANS OF CHLORINE FROM AURIFEROUS ORES, SAND, RESIDUES OF GOLD-
WASHING AND THE LIKE to be as follows:-
This invention relates to improvements in the process of extracting "gold by
means of Chlorine from auriferous ores, sand, residues of goldwashing et cetera.
The raw material, if containing sulphur must be roasted, the so called process of
chloruretting roasting being employed by preference. The product is washed and
the filtrate which may contain valuable metallic salts preserved.
If the material after roasting and washing is found to contain gold in somewhat
large grains, these may now be conveniently separated by washing or by other
mechanical means the heavy sulpho-metals being removed.
The material reduced to a sufficiently fine powder, whether roasted and
separated from the coarse grains of gold or not as circumstances may require, is
now subjected to the following process for the extraction of the gold.
A small quantity of hypochlorite of lime or of some other salt in which the
acid consists of Chlorine combined with oxygen, is dissolved in water or in some
other suitable liquid, such for instance as a solution of Chloride of sodium when
the raw material contains silver.
Instead of Chloride of sodium, chloride of calcium or some other substance
capable of dissolving chloride of silver may be employed. This solution should
contain about one per cent or less of hypochlorite of lime. This solution before it
enters the running tanks containing the auriferous material, meets with a highly
diluted solution of some acid, such as muriatic acid sulphuric acid, carbonic acid
or some other acid, the solution being of such a strength that equal volumes of the
acid and the hypochlorite of lime will just suffice for the decomposition of the
hypochlorite of lime.
The mixed liquids now percolate through the material whereby the chlorine
produced by the mixture partly in a nascent state unites itself with the gold which

page_text: is thereby dissolved, and is continually allowed to run off at such a rate that only
a small excess of Chlorine remains in the solution. This solution is led in to the
precipitation tanks; where the gold and any silver present, is precipitated by one
of the usual methods.
This method of extracting gold can be carried out in a convenient and cheap
manner without the escape of any considerable quantity of chlorine.
The solutions may also be stronger and be mixed beforehand, and then, after
a longer or shorter time be poured over the crushed raw material prepared in the
manner above described,

page_text: Improvements in the Process of Extracting Gold by Means of
Chlorine from Auriferous Ores, Sand, Residues of Gold
Washing, and the like.
I, HENRY MUNKTELL, of Falun, Sweden, Engineer, do hereby declare the
nature of my invention for "IMPROVEMENTS IN THE PROCESS OF EXTRACTING
GOLD BY MEANS OF CHLORINE FROM AURIFEROUS ORES, SAND, RESIDUES OF GOLD'
WASHING AND THE LIKE" and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement :-
This invention relates to improvements in the process of extracting gold by
means of chlorine from auriferous ores, sand, residues of gold washing et cetera.
The raw material, if containing sulphur, must be roasted, the so-called process of
chloruretting roasting being employed by preference. The product is washed and
the filtrate which may contain valuable metallic salts preserved.
If the material after roasting and washing is found to contain gold in somewhat
large grains, these may now be conveniently separated by washing or by other
mechanical means the heavy sulpho-metals being removed. The material reduced
to a sufficiently fine powder (and freed from protoxides) whether roasted aud
separated from the coarse grains of gold or not as circumstances may require, is
now subjected to the following process for the extraction of the gold. The finer
the powder the greater the quantity of gold that can be extracted. The powder
however should be sufficiently coarse to allow liquids to percolate through with ease.
A small quantity of hypochlorite of lime or some other salt in which the acid
consists of chlorine combined with oxygen, is dissolved in water or in some other
suitable liquid, such for instance as a solution of chloride of sodium when the raw
material contains silver.
Instead of chloride of sodium, chloride of calcium or some other substance
capable of dissolving chloride of silver may be employed. This solution should
contain about one per cent or less of hypochlorite of lime. This solution before it
enters the running tanks containing the auriferous material, meets with a highly
diluted solution of some acid, such as muriatic acid, sulphuric acid, carbonic acid
or some other acid, the solution being of such a strength that equal volumes of the
acid and the hypochlorite of lime will just suffice for the decomposition of the
hypochlorite of lime.
The mixed liquids now percolate through the material whereby the chlorine,
produced by the mixture, partly in a nascent state unites itself with the gold
which is thereby dissolved, and is continually allowed to run off at such a rate that
only a small excess of chlorine remains in the solution. This solution is led in to
the precipitation tanks, where the gold, and any silver present, is precipitated by
one of the usual methods.
This method of extracting gold can be carried out in a convenient and cheap
manner without the escape of any considerable quantity of chlorine.
The solutions may also be stronger and be mixed beforehand, and then, after a
longer or shorter time be poured over the crushed raw material prepared in the
manner above described; in this case however not only does much chlorine
escape which has a very detrimental effect on the carrying out of the process, but
also larger quantities of the solutions are required. By allowing the chlorine in

page_text: a very diluted solution to act on the auriferous substances and by producing this
chlorine at the same moment the solution is used, the process becomes extremely
convenient and inexpensive and the difficulties hitherto always met with when
chlorine is used on a large scale for the extraction of gold, are avoided.
The process can be carried out with very simple apparatus. A convenient
arrangement consists of tanks having a layer of filtering medium above a false
bottom. Over each tank are two vessels by which the quantities of the solutions
are measured. They are filled by means of pipes or conduits and discharged into
other conduits leading to the tanks. Other pipes or conduits carry water or other
liquids to the tanks for dissolving and carrying away the protoxides if any.
In the accompanying sheet of drawings Fig. 1 represents a simple arrangement
of an extraction apparatus, showing the tanks in a section on the line 1-1 in
Fig. 3. Fig. 2 is a longitudinal section thereof along the line 2.-2. in Fig. 1 ; and
Fig. 3 represents the same in plan and horizontal section along the line 3.-3. in
Fig. 1.
a. a are extraction tanks of wood; bb represent filtering bottoms inside the
tanks consisting of a layer of gravel or quartz spread on perforated boards_or
plates of earthenware, b', placed on the supports b². c. c are outlet cocks. For
measuring the requisite proportions of the solutions of hypochlorite of lime, and
the acid, the tubs d. d and e. e are placed on the channels f. f and g. g above the
tanks. The diluted ready made solutions of hypochlorite of lime and acid are led
As
separately through the channels h h and ii into the respective tubs & and e.
each tub is filled, the plug k is inserted into the hole in the channel leading to
that tub.
The channels ff are used for admitting such acids and salt solutions as are
required for dissolving other substances than gold. L. Z are water pipes.
After the tubs have been filled the process is commenced by removing the plugs m
and the diluted solutions of hypochlorite of lime and acid are allowed to run in
definite quantities out of the tubs d and e into the channels g meeting.cach other
at the openings nn and thus running down together into the material in the tanks.
By cross boards o in the channels the tanks which are not to be operated upon
can be shut off. p. 1, p are channels to discharge the solutions which are running
off or are let out from the tanks u. By means of short shoots placed under the
cocks c the liquid is led into the respective channels p.
Lines of rails q for transporting the material are also shown on the drawings.
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
In extracting gold by means of chlorine from auriferous ores et cetera free or
freed from sulphur, causing a mixture of a diluted acid with a diluted solution of
bypochlorite of lime or some other chlorine generating salt, (together if necessary
with chloride of sodium or some other substance by which chloride of silver
is dissolved) to pass through the crushed materials these being freed from pro-
toxides and kept in open tanks and the passing through of the said mixture being
continued so long as any traces of gold (worth recovery) are to be found in the
solutions running off, substantially as described.
Dated this twenty seventh day of August 1885.