IMPROVEMENTS IN OBTAINING SOFT LEAD PROM HARD LEAD, FOR THE SEPARATION OF THE IMPURITIES IN HARD LEAD, AND FOR THE SEPARA- TION OF ANTIMONY FROM THESE IMPURITIES
Year: 1854

page_text: LETTERS PATENT to Edmund Alfred Pontifex, of Shoe Lane, in the City
of London, and Charles Glassford, of Ashburnham Grove, Greenwich, for
the Invention of "IMPROVEMENTS IN OBTAINING SOFT LEAD PROM HARD LEAD,
FOR THE SEPARATION OF THE IMPURITIES IN HARD LEAD, AND FOR THE SEPARA-
TION OF ANTIMONY FROM THESE IMPURITIES."
Sealed the 22nd September 1854, and dated the 26th July 1854.
PROVISIONAL SPECIFICATION left by the said Edmund Alfred Pontifex
and Charles Glassford at the Office of the Commissioners of Patents, with
their Petition, on the 26th July 1854.
We, EDMUND ALFRED PONTIFEX, of Shoe Lane, in the City of London, and
CHARLES GLASSFORD, of Ashburnham Grove, Greenwich, do hereby declare the
nature of the Invention for "IMPROVEMENTS IN OBTAINING SOFT LEAD FROM HARD
LEAD, FOR THE SEPARATION OF THE IMPURITIES IN HARD LEAD, AND POR THE
.SEPARATION OF ANTIMONY PROM THESE IMPURITIES," to be as follows:-
The object of this Invention is to obtain from hard lead the soft lead which
it contains, and at the same time the antimony, which constitutes one of the
chief impurities that renders it hard. This we do by a more economical and
effective method than has been hitherto in use. We operate upon the hard
lead while undergoing the process of calcination in calcining furnaces. The
ordinary calcining process has for its object the separation of the impurities by a

page_text: lengthened exposure of the hard lead' (while in a melted state in suitable fur-
naces) to the action of the air, thereby chiefly oxidising the impurities contained,
converting a portion into a slag, which requires to be constantly removed from
the surface as it forms, and another portion being volatilized and carried off'
as fume through the flues, to the serious loss of the metal operated upon, and
to the production of highly destructive and unhealthy vapours.
Our Invention so operates upon the melted lead that the whole of the
impurities are rapidly oxidised and readily removed;. that the lead and
impurities are not lost by being carried away as fumes up the chimney, but
also so that the whole of the antimony (which is the chief purity in hard lead)
is separated and obtained, and may afterwards be treated especially to procure
the antimony pure and free from all the other impurities.
Our improvements consist, firstly, in acting upon the lead with a mixture of
alkalies and alkaline salts, or with either of these substances separately, which
is found to facilitate the rapid oxidation of the metals and other substances,
which render the lead hard and impure. For this purpose we prefer to employ
a mixture of nitrate of soda or nitrate of potassa, carbonate or sulphate of soda,
and caustic lime; but other salts of the alkalies may be used, although we
prefer the use of the materials stated above, as being the most economical,
certain, and satisfactory. These alkaline matters may also be used separately,
the nitrate of soda being quite capable of being used alone for the oxidising
of the impurities; but we find that the result is best when the nitre is used
with the caustic lime, or with an admixture of the soda ash or other similar
carbonate and with caustic lime.
By these means the antimony, arsenic, tin, copper, silica, and other impurities
contained in hard lead are oxidised and combined with the alkaline matters
used, so as to form a dross or slag containing all these matters together or with
some lead. The result, after sufficient time and materials have been employed,
is the production of a beautiful, soft, and ductile lead, suitable for every purpose
to which soft lead is applied in the arts; the production also of a dry dross,
which contains the whole of the antimony and other metals and substances
abstracted from the lead, together with a small portion of the lead, from which
the antimony may be readily obtained.
The second part of the Invention has for its object the recovery of the
antimony from the other impurities which have been thus separated from the
hard lead.
The dross or slag contains antimony, arsenic, and silica combined with the
alkaline matters used, but chiefly with the soda, and also contains lead and

page_text: copper in the form of oxides. These may all be separated from each other by
the application of known means; but we treat the pulverized dross with as
much acid, sulphuric, nitric, or acetic, as will combine with the metallic and
alkaline matters; these we remove by subsequent washing, in such a manner
that the insoluble residue or matter remaining unacted upon is chiefly oxide of
antimony or antimonic acid. This residue may now be treated with finely
pulverized carbon, subjected to heat, and the metallic antimony obtained.
When it is desired only to obtain an alloy of lead and antimony, rich in the
latter, it is only necessary to at once act upon the dross from the hard lead to
de-oxidise the oxides present, and to obtain the lead and antimony separate.
The arsenic, sulphur, silica, and copper (if the operation is carefully con-
ducted) remain with the cinders resulting from the reduction. And it may
be remarked, as another advantage resulting from the application of our
method, that a much smaller quantity of the silver contained in the hard lead
is carried off in the drosses than is abstracted in the ordinary process of
calcining hitherto in use.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Edmund Alfred Pontifex and Charles Glassford in the Great
Seal Patent Office on the 26th January 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, EDMUND
ALFRED PONTIFEX, of Shoe Lane, in the City of London, and CHARLES GLASS-
FORD, of Ashburnham Grove, Greenwich, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of July, in the year of our Lord
One thousand eight hundred and fifty-four, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto us, the
said Edmund Alfred Pontifex and Charles Glassford, Her special license that
we, the said Edmund Alfred Pontifex and Charles Glassford, our executors,
administrators, and assigns, or such others as we, the said Edmund Alfred
Pontifex and Charles Glassford, our 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 OBTAINING SOFT LEAD FROM HARD LEAD, FOR THE SEPARA-

page_text: TION OF THE IMPURITIES IN HARD LEAD, AND FOR THE SEPARATION OF ANTIMONY
FROM THESE IMPURITIES," upon the condition (amongst others) that we, the said
Edmund Alfred Pontifex and Charles Glassford, by an instrument in writing
under our hands and seals, or under the hand and seal of one of us, 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Edmund Alfred Pontifex, on behalf of
myself and the said Charles Glassford, do hereby declare the nature of the
said Invention, and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement
thereof (that is to say):-
The process is peculiarly applicable to the improvement of the lead known
and sold in the market as hard Spanish lead, hard German lead, and to such
other leads as are crystalline, whitish, and break upon being hammered or
rolled. The chief impurities found in these crude leads are antimony, silica,
copper, tin, arsenic, and sulphur. The method hitherto practised has been
to calcine or roast the melted lead in reverberatory furnaces, in which the
lead was fully exposed to the action of the heated gases and air from the
fire-place; by this means the impurities in the lead were slowly oxidized,
and then carefully removed from the surface by rakes, as a slag or dross.
Large quantities of the lead were also oxidized, and removed with the
impurities. Much silver, was also lost if tho lead were rich in it, and from
tho great length of time, expense, and loss involved by this tedious process,
the purification of very hard lead was quite impracticable. By our method,
the lead is similarly exposed in the melted state in reverberatory furnaces,
but is freed from impurities in much less time than is usually required, and
the whole or nearly the whole of the antimony is obtained, in place of being
all or nearly all lost by volatilization. The process is also more economical,
and yields very pure and malleable lead. The process can be adopted in the
existing calcining or improving furnaces, and is as follows:-For lead con-
taining from three to fifteen per cent. of antimony, we find it best to apply a
mixture of the following materials, in the proportion of three parts by weight
of nitrate of soda (cubic nitro): four parts of soda ash and four parts of
caustic or burnt lime; for a lead which does not contain more than two or
three per cent. of antimony, and contains from half to one or one and a hal
per cent. of silica, we find it best to employ a mixture only of equal parts soda

page_text: ash and caustic lime; these are the proportions that have been found
best in practice. The preparation of the mixture or of the materials is
very simple, and may be thus described:-The necessary quantity of burnt
lime is spread out on a floor; warm water is sprinkled over it until it is
perfectly slacked and falls into a fine powder; it is then passed through a
fine sieve to separate any small stones or flints. The requisite quantities of
alkali and of nitre are added, the whole well mixed with a shovel, and again
passed through a sieve, so as to blend the whole intimately together. When
only the alkali and lime are to be used, the alkali or part of it may be first
dissolved in the water required for the hydrating of the lime, and then the
solution is to be intimately mixed with the lime, and it is advisable to separato
any flinty matter that may be contained in the lime. The application of these
matters mixed or separate to the purification of the lead is thus effected :-The
melted lead in the furnace, a few hours after it has been poured or run into
the pan,
is carefully skimmed with an iron rake, and the whole of the drossy
matter is removed, by being drawn to the side door of the furnace and then
raked out; one, two, or more pounds of the mixture or materials above
mentioned are then scattered as evenly and as uniformly as possible over the
bright surface of the hot lead. The doors of the furnace are then closed for a
short time, but from time to time opened to observe when a brown or yellowish
brown cake of drossy matter has collected over the surface, which will generally
be in about ten to twenty minutes. The doors are again to be shut, fresh
fuel thrown upon the fire, and when the smoke has cleared away, and the fire
becomes bright, which will be in a few minutes, the crust or covering of dross
.is carefully skimmed off and removed, and a fresh application of the alkaline
matter introduced. This is repeated until it is found that the lead has become
perfectly malleable and ductile, which is easily known by examining samples of
the lead withdrawn during the operation, as is well known by those conversant
with such metallurgical operations. It is found best to keep the lead in the
furnace constantly at a red heat, or so hot that the iron vessel which contains
the lead is constantly at a low red heat. The dross from the surface of the
lead becomes of a brighter yellow or brown color as the operation approaches
completion and as the impurities decrease. The quantity of material required
will vary according to circumstances; but we find that of the alkaline mixture,
5 first described, no more need. bo used in twenty-four hours' operations than
55 lbs. of the compound, when about nine to ten tons of lead aro being
operated on, and when using the other compound not more than from 40 to
60 lbs. during the twenty-four hours.

page_text: The treatment of the drosses for the recovery of the metals containd, and
which have been separated chiefly in the state of oxide by and with the alkaline
matters, may either be made in the reducing furnace in the ordinary way, or
subjected to the following operation, which has for its object the separation of
the lead and antimony from each other. When it is found by assay that the
dross contains not more than 12 to 15 per cent. of antimony, it will be found
always advisable to reduce the dross in the usual way in the ordinary reducing
furnace, and subsequently to treat the metal thus obtained as follows:-Tho
reduced lead is melted in a pot, taking care not to heat it so far that white
fumes are given off, or so far that a strong disagreeable odour is perceived, but
so as to obtain it as liquid as possible. Withdraw the fire under the pot to
allow the melted metal to cool down, and after a few minutes withdraw from it
by means of a collander ladle, (such as is constantly used in the crystallizing
or desilverizing of lead,) the pulpy or pasty part of the lead, until the whole or
greater part appears to be removed. The portión taken out in this way will be
found to be much richer in antimony than the portion that remains more liquid
in the pot, and the reduced lead may thus be separated into lead that may
economically be again subjected to the calcining process for pure lead, and into
a portion sufficiently rich in antimony as to permit its sale as antimonial lead.
Finally, the drosses may be thus treated to perfectly separate the antimony
from the lead-The pulverized dross is to be treated with boiling water, which
by proper treatment will remove all but the oxides of antimony and of lead.
These are to be subjected with the assistance of heat to the slow action. of nitric
acid, whereby the whole of the oxide of lead is dissolved out, and the residue
will consist nearly entirely of antimony in union with oxygen. To obtain the
antimony perfectly pure from this residue it is only necessary to reduce it by
the present known and practised methods. The lead solution may be evaporated
for the production of crystals of nitrate of lead.
It is not necessary here to refer to the other constituents that may be freed
from the lead and exist in the dross, as none of these exist in quantity sufficient
to render them of any practical value."
Having thus described the nature of our said Invention, and the manner of
performing the same, we would have it understood that although we have
mentioned soda, it will be evident that potash may be used in place thereof, and
other alkaline salts may be employed, but not, we believe, so advantageously;
and although we have been particular in giving exact particulars of the process
as performed by us, we do not confine ourselves thereto; but what we claim
is, the treating hard and impure leads with alkaline matter to separate the

page_text: impurities, but more especially the antimony and silica in a much more efficient
and rapid manner than has hitherto been done; and we also claim the
separating the antimony from the dross obtained by the process above described.
In witness whereof, I, the said Edmund Alfred Pontifex, have hereunto
my hand and seal, this Twenty-fifth day of January, in the year of
our Lord One thousand eight hundred and fifty-five.
Witness,
H. W. CARPMAEL.
EDMUND A. PONTIFEX. (L.S.)