IMPROVEMENTS IN SMELTING COPPER AND OTHER ORES
Year: 1847

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, T, WILLIAM
BIRKMYRE, of Southdown, Cornwall, Chemist, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of
Great Britain and Ireland, bearing date at Westminster, the Sixteenth day
of November (One thousand eight hundred and forty-seven), in the eleventh
year of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said William Birkmyre, my exors, admors, and assigns, Her
especial licence, full power, sole privilege and authority, that I, the said
William Birkmyre, my exors, admors, and assigns, or such others as I, the
said William Birkmyre, my exors, admors, or assigns, should at any time
agree with, and no others, from time to time and at all times during the
term of years therein expressed, should and lawfully might make, use, exer-
cise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, in the Islands of Jersey, Guernsey, Alderney, Sark, and Man, and
in all Her Majesty's Colonies and Plantations abroad, my Invention of
"IMPROVEMENTS IN SMELTING COPPER AND OTHER ORES;" in which said Letters
Patent is contained a proviso that I, the said William Birkmyre, shall cause
a particular description of the nature of my said Invention, and in, what
manner the same is to be performed, by an instrument in writing under my
hand and seal, to be inrolled in Her said Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
in part recited Letters Patent, as in and by the same, reference being there-
unto had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
William Birkmyre, do hereby declare, that the nature of the said Invention,
and the manner in which the same is to be performed, are fully described
and ascertained in and by the following description thereof, that is to say :-
My Invention relates to the common ores of copper, silver, lead, tin, and
antimony, which ores are usually sulphurets or arseṇurets, and occasionally
arseniates, carbonates and oxides of some of the said metals. But the ores
which are best adapted for the improvements herein. described are sulphurets
and arsenurets, and are well known to chemists and others under the names of
copper pyrites (sulphuret of copper and iron), copper glance (disulphuret of
copper), variegated copper ore (disulphuret of copper and sulphuret of iron),
tin pyrites (cupreous sulphuret of tin), white copper ore (arsenuret of copper),
fahl ore (sulphurets of copper," arsenic, antimony, iron, zin, and silver), argenti-
ferous sulphurets of copper, lead, and antimony, and also, but in a minor
degree, to the peroxide of tin and the carbonates and oxides of copper when
they are contaminated with sulphurets, arsenurets, and arseniates.
And in order that this Invention may be fully understood, I will now
proceed to state that it has for its objects, first, to abate the nuisance arising
from the volatilization of the sulphur in the state of sulphurous and sulphuric
acids, and the arsenic, either in the metallic state or that of arsenious acid,
in the ordinary process of smelting copper, and to save about two thirds of the
sulphur of the common ores by converting it into sulphuric acid, and the most
part of the remainder of the sulphur into salts formed of sulphuric and the
oxides of copper, iron, or zinc, by roasting the common ores of copper in a
pulverized state (fine dressed copper ore) on trays in iron pyrites kilns by the
heat evolved during the combustion of iron pyrites (mundic), thereafter, to
lixiviate and to extract, by the well-known processes of cementation or electro-
metallurgy, one fourth of a per cent. more pure copper from seven and a half
per cent. ores than is obtained by the ordinary process of smelting, and
by the same processes to extract from the sulphurėt of silver, and particularly
from sulphuretted copper ores as have been proved rich in silver by assay or
analysis. Secondly, instead of using a nitrate and sulphuric acid alone in a
nitre pan in the ordinary way, to mix on a tray a nitre (in the same proportion
relative to the sulphur as heretofore) with any of the above-named ores, then
to calcine the mixture on the said tray in a mundic kiln, so that the nitrate of
potash or of soda shall serve at the same time to supply the vitriol chamber
with the deutoxide or other oxides of nitrogen (indispensable in the manu-
facture of vitriol on the large scale), and to oxide at least a portion of the
sulphur and the arsenic of the ores by converting them into a sulphate and
"
:

page_text: arseniate of potash or soda, which may be: separated by water. In 'the
extraction of copper by roasting the common ore of copper (copper pyrites,
usually impure; containing..sulphurets of zinc, lend, and other metals, also
arsenurets with siliceous matters); it...is comparatively easy to volatilize the
sulphur. of the iron and zinc.. in the state of sulphurous and, sulphuric acids,
especially from the..former: metal; but the sulphur in combination with the
copper becomes iú a great measure.sulphuric, acid by combining with oxygen,:
and the copper being oxidized the acid and oxide combine to form.ȧ sulphate
of copper, as. I have found by, experiment, and the acid adheres, with great
tenacity to the peroxide of copper, and it. is from this cause, that so many
roastings, meltings, &c., are required to free the copper from its sulphur in the"
common process of smelting copper. I have also.found,by: experiment that the
sulphate of copper may (after..the common ore, has been submitted to a strong
heat) be easily dissolved.out nearly pure at a lower heat, however this sulphate:
may contain more of sulphates of iron, zinc, or silver than, sulphate..of
copper.
* ..
..I now proceed to state, according to my experience, the best manner of
carrying the above improvements into effect. The iron pyrites, kilns are to be'
constructed of the common form, but which it is unnecessary to': describe as '
they are well known;. I would, however, recommend, that. the ashpits be pro-
vided with an iron or leaden cistern for holding water, in order to abate the
temporary. nuisance of the sulphurous; and sulphuric acids when withdrawing
the ashes of the iron pyrites, and which cisterns, should have a sliding cover to
prevent the undue evaporation of water into the kilns. The outside dimen-'
sions of the pair of kilns (for the quantities herein-after directed to be operated
upon): may conveniently.be in, length; thirteen feet, breadth seven feet four.
inches, height nine feet; the inside diameter of each kiln should be five feet,"
and is best: constructed of the form of an octagon, and lined with fire bricks. *
In each kiln there should be placed upon two or three stout iron bars, just
above the charging, door for the, mundic, an iron or copper tray, or one of iron
coated on. the inside with stoneware or porcelain, which, tray should be four
feet and a half, long by three feet and a half wide, with a rim three or four
inches high. These dimensions: readily permit the hot air and the acids to
pass through the pipe, at the top of each kiln into the vitriol chamber. The
charging doors-of each. kiln should be. provided with, an air, hole and a sliding
damper, as much of the success of making vitriol by mundic depends upon
the admission of air-above the mundic, as well as that which is required to pass
through the ashpit to support combustion: At the side of each. kiln, and on
aline with the tray, there should be a narrow opening for the tray containing
ر
3

page_text: the roasted ore to be pulled out and then emptied for lixiviation into a lead
cistern placed about three feet below, which cistern should be supplied with
hot water from the cooling cistern of the kilns, after which the tray may be
charged anew with a mixture of lixiviated and fresh ore either by a shovel
or by a hopper at the top of the 'kiln. The vitriol chamber for this pair
of kilns may be one hundred and fifty and a half feet long, eleven and
a quarter feet wide, and eight feet high, and the length divided into three
parts, technically bottoms. The first compartment, that which is nearest
to the kilns, should have its acid kept apart, being comparitively impure;
while the acid in the second and third compartments is equal to that from the
best sulphur. The above dimensions of kilns and vitriol chamber are suffi-
cient for the one to calcine two tons of copper ore per diem, and the other to
make in the same time from the copper ore and mundic three tons of sul-
phuric acid, specific gravity 1.847. As much uncertainty prevails as to the
hourly produce of vitriol in a chamber, I recommend the following arrange-
ment, which will show quickly and accurately the produce of vitriol:-For each
compartment of the vitriol chamber there is required a stout glass tube, about
twenty-two inches long, which is bent at six inches from one end to a right
angle, and the long side (sixteen inches) graduated into inches and tenths.
The short leg of the tube is then inserted into a piece of half-inch lead pipe
(previously soldered into a hole close to the bottom of the turned-up lead) so
as to penetrate to the inside of the chamber, and the space between the tube
and the pipe made tight by luting. About a foot from each of these glass.
tubes is fastened a double-curved lead syphon, one leg of which is inserted
under the bottom of the side Icad of the chamber, which syphon is supplied
with a mouthpiece, and has at the top bend a small orifice for admitting air.
In taking an observation it is first necessary to blow down the graduated tube
to expel the acid into the chamber. On withdrawing the mouth the true
depth of the inside of the chamber is seen on the tube; then, by placing the
four finger of the one hand on the small hole of the syphon, and with the
other closing the lower aperture, and withdrawing the air by the mouthpiece,
the acid quickly flows, and continues so long as no air is admitted by the
small aperture. On testing this acid by the hydrometer (which, however,
should be occasionally compared with a standard hydrometer or a specific
gravity bottle, as vitriol corrodes the common flint-glass hydrometer, much
more than alkali,) the real strength of the acid is known, and the produce
determined.
Now, in relation to the working of this Invention, about ten hundredweight
of the iron pyrites, in pieces of the size of a walnut, are to be shovelled into

page_text: one of the kilns (previously lighted, and nearly charged with iron pyrites); and
at the end of six hours a similar charge may be put into the other kiln (also
previously kindled), and so on alternately with each kiln. Thereafter with-
draw, about eight hundredweight of mundic ash for every charge of ten
hundredweight mundic containing forty per cent. sulphur, as for every
thirty-two of sulphur that it loses it gains only twelve of oxygen, but the
sulphurets of copper and of the other metals herein specified lose very little
weight. On the contrary, when the ores are good, and the process' well con-
ducted, they gain fully, as much in oxygen as they lose in sulphur. I gene-'
rally find that good copper pyrites gains 4 per cent. in weight. The charge
of copper ore for each tray may be about one cwt. and a half, and should be
evenly spread so as to form a layer of between one and two inches thick.
The ore should be turned over now and then by a rake, in order to expose it'
equally. After it has been roasting for about an hour it may then be thrown'
into the lead cistern, and lixiviated with hot water. The solution should.
immediately be run off into leaden pans, heated and acidulated with sulpliuric'
acid, so as to prevent the formation of a subsalt when precipitating the copper
of the sulphate of copper by iron or zinc. In these leaden pans the copper.
may be obtained pure on the second day from the ore, as it is very quickly
precipitated at a boiling heat; for I find that a square foot of iron weighing
six lbs. precipitates two lbs. five oz. of copper in an hour, which is at least
fifty times faster than if it were left to be precipitated undisturbed in the cold;
but much of this time may be saved, even in the cold, with the further advan--
tage of obtaining the copper in mass, or electrótypes, such as sheets or rolls
(technically copper shells), by dissolving the iron or zinc (according to the
electro-metallurgic process) in sulphuric acid in a separate vessel, and connect-
ing either of these metals by a wire to the object to be copied in the solution
of copper. It generally takes two roastings to extract by lixiviation all the
copper. For the second roasting I prefer to mix with the lixiviated ore iron
pyrites or fresh copper ore, and then to treat as before mentioned. The
resulting solution of sulphates of iron and zinc (a by-product) I have used
with great advantage in purifying green soda leys previous to crystallizing the
washing soda of the shops. The quantity of this solution which should be
used is one imperial gallon at forty degrees Twaddell's hydrometer to thirty-
three imperial gallons impure soda ley's at fifty degrees. After boiling this
mixture to fifty-four degrees, and allowing it to settle, it should then be
drawn off into cast-iron pans to crystallize. The small addition of the métallic
solution, besides separating the sulphur of the sulphuret of sodium; 'a's 'sul-
phuret of iron and zinc, affords, by the double decomposition, the proper quan-
tity of sulphate of soda (carbonate of soda crystallizing best when a small

page_text: quantity of sulphate of soda is present) to dispose the carbonate of soda to
form large and fine crystals. The process of calcining which has been
described may be varied by placing one and a half cwt. of the fresh ore, on
the tray, and then adding a hot solution containing nine pounds, saltpetre or
eight pounds cubic nitre (the solution possessing the advantage over the dry
salts of 'dispensing with steam from a steam boiler for the vitriol chamber), or.
eighteen pounds saltpetre may be used, provided the quantity of any of the
said ores is only one half the weight of the iron pyrites. The orė may also
be mixed from the first with sixteen per cent. of saltpetre, and ten per cent..
of vitriol, specific gravity 1750; or fourteen per cent. of cubic nitre with the
samé quantity of vitriol, or these salts with the vitriol may be used after the
ores have been oxidated by calcination. The deutoxide of nitrogen thus:
developed is advantageously used for converting the sulphurous acid of the
burning iron pyrites into sulphurous acid, and the remainder of the sulphur
and arsenic of the said ores into a sulphate and arseniate: When the action
has ceased the sulphate and arseniate of potash or soda. are dissolved-out of.
the calcined, ore and saved. The washed, ore; now freed in a great measure.
of its sulphur, may be treated with a small quantity of sulphuric acid 'to.
dissolve any
oxide of silver or copper. The silver of the sulphates may be
separated at once from the copper and other metals by metallic copper, or it.
may be precipitated as a chloride by muriatic acid (hydrochloric acid) or.
common salt and pure silver, obtained by fusing the chloride with an alkaline.
carbonate. The argentiferous ores of lead, and antimony, and the impure.
peroxide of tin, should, after being thus purified, be reduced with carbonaceous
matter in the ordinary reducing furnace..
:
Having thus described the nature of my Invention, and the best means. I.
am acquainted with for performing the same, I would have it understood that.
I do not confine myself to the precise details herein described, provided the;
peculiar character of my Invention be retained; but what I claim is;-.
Firstly, the roasting or calcining separately the ores of copper and the ores
of the metals berein specified, by placing these ores in an open vessel in a.
undic: kiln, so that the vapours from its contents shall escape freely, with the.
vapours of combustion of the iron pyrites; and be condensed at the same time>
in the vitriol chamber.
Secondly, I claim the disengaging simultaneously from an open vessel in a
mundic kiln. the deutoxide of nitrogen for the vitriol chamber with, that of
oxidating the said ores, by mixing with the said ores saltpetre or cubic nitre.
"Thirdly,. I claim the supplying the vitriol chamber with steam, by using a
solution of saltpotre: or of cubic nitre with the said ores.
Fourthly, I claim the action of sulphuric acid upon the said ores after they

page_text: have been treated with saltpetre or cubic nitre, and either before or after they
have been freed from the sulphate and arseniate of potash or soda.
In witness whereof, I, the said William Birkmyre, have hereunto set my
hand and seal, this Sixteenth day of May, in the year of our Lord One
thousand eight hundred and forty-eight.