IMPROVEMENTS IN EXTRACTING COPPER, IRON, LEAD, BISMUTH, AND OTHER METALS OR MINERALS FROM TIN ORE
Year: 1843

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
MICHELL, of Calenick, in the County of Cornwall, Tin Smelter, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Eleventh day of April, in the sixth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Michell, Her especial licence, full power, sole privilege and authority,
that I, the said John Michell, my exors, adñiors, and assigns, or such
others as I, the said John Michell, my exors, adñiors, 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, exercise, and vend, within England, Wales, and the Town
of Berwick-upon-Tweed, my Invention of "IMPROVEMENTS IN EXTRACTING
COPPER, IRON, LEAD, BISMUTH, AND OTHER METALS OR MINERALS FROM TIN
ORE;" in which said Letters Patent is contained a proviso, that I, the said
John Michell, shall cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, 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 thereunto bad, will more fully and at large
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
John Michell, do hereby declare that the nature of my said Invention, and
the manner in which the same has to be performed, are fully described
and ascertained in and by the following statement thereof, that is to say :-

page_text: In the usual method of dressing tin ore much difficulty is experienced in
separating the other metals or minerals which are mixed with the tin ore. Now,
the object of the present Invention is to obtain tin ore more pure, and this is
to be effected by dissolving such of the other metals or minerals as are soluble
by means of acids, the acid so employed to dissolve the other metals and
minerals not injuriously acting on the oxide of tin.
And in order that my Invention may be most fully understood, I will proceed
to explain the means pursued by me :-
Tin ore is to be pulverized, as heretofore, and the greater portion of the
matrix separated by washing, as is well understood; the ore is then, by
preference, to be calcined and treated with acid in order to dissolve the foreign
metals or minerals, when such foreign metals or minerals so dissolved may be
readily washed off and separated from the tin ore, such foreign metals con-
sisting of small quantities of copper, iron, lead, bismuth, and other metals and
minerals, and it is well know that very small quantities of such foreign metals
or minerals materially affect the quality of the tin. The quality and character
of different tin ores in some degree vary, and will consequently require the
processes herein described to be modified; but the workman, with a moderate
extent of experience, aided by careful observation, will readily vary the process
to suit the various sorts of tin ore. So far as my experience goes, I have found
that the best time of submitting tin ore to the action of acid is whilst they are
warm, after removing them from the calcining process.
In using acid for the purpose of dissolving the foreign metals or minerals, so
that they may be separated from the tin by washing, I prefer to employ
muriatic acid; and I usually find it desirable to dilute the acid with about an
equal quantity of water, such diluted acid being either poured on to the ores
contained in suitable vessels or tanks, or the ores may be gradually thrown
into the diluted acid contained in suitable tanks or vessels, and the tin ores are
to be allowed to remain three or four days, or a longer period if necessary,
subject to the action of the acid; the time, however, during which the ores are
submitted to the action of acid is not material, so long as sufficient time
be allowed for the purpose, the ores being subjected to the action of acid
beyond the time actually necessary for dissolving the foreign metals or minerals
not being injurious, and is simply the waste of time. The quantity of muriatic
acid which I have found necessary is about one hundredweight of the ordinary
acid of commerce for each ton of ore, but in some cases a larger proportion of
acid will be necessary; and in some cases, where the foreign metals are in a
state of oxide, it will not be absolutely necessary to calcine the ores before
operating with acid. The process of dissolving the foreign metals or minerals

page_text: being completed, the ores are to be well washed in water, by which the dissolved
metals or minerals will be extracted or separated from the tin ore.
cases it may be expedient to apply heat in order to hasten the process and
lessen the quantity of acid. This may be effected by putting the oro with the
acid into earthenware vessels, which may be placed in a sand bath.
Having thus described the nature of my Invention, and the best means
I am acquainted with for performing the same, I would remark, that although
I have named muriatic acid, I do not confine myself thereto, nor do I confine
myself to any of the details herein described, so long as tin ores are operated
on by acid, so as to dissolve the foreign metals or minerals therein, and
thus allow such foreign metals or minerals to be washed off or separated from
the tin ores; and I would remark, that I do not claim the dissolving of copper,
iron, lead, bismuth, and other metals or minerals contained in ores generally,
by means of acid, the Invention being confined to the treating of tin ores with
acid, in order to dissolve such foreign metals or minerals, and so that they may
be separated or extracted from the tin ore by means of washing.
I would remark, that although I prefer to use the acid employed in the
liquid state, as above described, it will be evident that acid in vapour evolved
from any process may be caused to act in order to dissolve such foreign metals
or materials and purify the tin ores.
And I wish it to be understood that what I claim is, the mode of purifying
tin ore by extracting foreign metals or minerals by dissolving them in acid, and
washing them off or separating them, as above described.
In witness whereof, I, the said John Michell, have hereunto set my
hand and seal, this Fifth day of October, in the year of our Lord One
Enrolled the Ninth day of October, in the year of our Lord One
thousand eight hundred and forty-three.