IMPROVEMENTS IN THE PROCESS OP SOFTENING AND PURIFYING LEAD
Year: 1860

page_text: LETTERS PATENT to William Baker, of Sheffield, in the County of
York, Chemist, for the Invention of "IMPROVEMENTS IN THE PROCESS
OP SOFTENING AND PURIFYING LEAD."
Sealed the 18th December 1860, and dated the 21st June 1860.
PROVISIONAL SPECIFICATION left by the said William Baker at the
Office of the Commissioners of Patents, with his Petition, on the 21st
June 1860.
I, WILLIAM BAKER, of Sheffield, in the County of York, Chemist, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE PROCESS
OF SOFTENING AND PURIFYING LEAD," to be as follows:-
This Invention relates to a peculiar process for purifying lead, whether in
the state of "pigs," or in that known as "slag lead;" or the same process may
be applied to lead when in the "improving" or any other suitable furnace.
It is well known that lead frequently contains a number of impurities, con-
sisting principally of sulphur, antimony, arsenic, and iron, the presence of
which greatly impairs the softness or ductibility of the metal, and according to
my Invention I propose to remove these impurities, and consequently soften
and purify the lead by the admixture therewith, when at a suitable tem-
perature, of oxydising agents. The agents I have found most efficacious are
the nitrates and bi-sulphates of soda and potass, but other salts may be advan-

page_text: tageously employed, such as the sulphate of iron, a mixture of bi-sulphate
of potass, or soda and common salt in equivalent proportions; the hypo-
chlorites of lime, potass, and soda, the chlorates of potass and soda, or a
mixture of any or all of the above-named salts. These salts, or combinations
of them, are used either in a fused or unfused state, and are stirred into the
molten lead by a ladle or other convenient tool, whereupon the oxidised
products and impurities rise to the surface, and may be skimmed off in the
form of dross. The lead so treated is found to be both pure and soft, and
capable of being rolled or worked to any extent. The quantity of oxidising
agent employed depends, of course, on the greater or less impurity of
the lead.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Baker in the Great Seal Patent Office on the 21st
December 1860.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
BAKER, of Sheffield, in the County of York, Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of June, in the year of our Lord
One thousand eight hundred and sixty, in the twenty-third year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said William Baker, Her special license that I, the said William
Baker, my executors, administrators, and assigns, or such others as I, the
said William Baker, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times there-
after 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 "IMPROVE-
MENTS IN THE PROCESS OF SOFTENING AND PURIFYING LEAD," upon the condition
(amongst others) that I, the said William Baker, by an instrument in
writing under my hand and seal, 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 Baker, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-

page_text: formed, to be particularly described and ascertained in and by the following
statement, that is to say:-
This Invention relates to a peculiar process for effecting the purifying and
the softening of hard or impure lead. Lead, as it occurs in commerce, fre
quently contains a number of impurities, consisting principally of sulphur, anti-
mony, arsenic, iron, and other metals, the presence of which greatly impairs its
softness and ductility. Now, the object of my Invention is to remove these
impurities and to soften and purify the lead, and this Í effect by the admix-
ture of oxidising agents with the lead when at a temperature higher than its
melting point. The oxidising agents I have found most efficacious are the
nitrates and the bisulphates of soda and potash; but other salts, which at a
high temperature acts as oxidising agents, may be advantageously employed,
such as sulphate of iron, a mixture of bisulphate, of soda, or potash with
common salt or chloride of sodium; the hypochlorites of lime, soda, and potash.
the chlorates of potass and soda, or a mixture of any of the above-named salts
or compounds. These salts, or mixtures of them, may be used either in a state of
division or in a fused or fluid condition, and when employed in either condition
are to be incorporated with the molten lead contained in a suitable pot or vessel
by means of a ladle or other convenient instrument. Upon such admixture
the oxidised products and impurities will rise to the surface and may be
skimmed off. The lead having been so treated will be found to be both purer,
softer, and better capable of being rolled or worked. The proportions of the oxi-
dising agents employed depend of course on the amount of impurity existing in
the lead. I have found that in the treatment of impure lead, such as that known
as English slag lead, and to which my process is more especially applicable that
the following proportions may successfully be employed. When I employ the
nitrates of the alkalies, I use them in the proportion of one part by weight of the
dry salt to every one hundred parts by weight of lead. In subjecting the impure
lead to the action of the bisulphates of soda and potass I then employ them in
the proportion of two parts by weight of either of the bisulphates of potass
and soda to every one hundred parts by weight of lead. When I employ the
hypochlorites herein-before mentioned, or sulphate of iron, or a mixture of the
bisulphates of potash or soda with common salt, then I use the same in the
proportion of three parts by weight to every one hundred parts by weight of
lead. Although I have found these proportions to effect the softening of
certain classes of hard slag or impure lead, I do not confine or restrict myself
to any of the before-mentioned proportions.
I am aware that it has been proposed to effect the softening of hard lead,
and more especially of those impure descriptions of lead, known as hard,

page_text: Spanish, or other antimonial leads by subjecting such leads in a reverberatory
or calcining furnace to the oxidising action of air, as is well known and under-
stood, together with the employment of certain nitrates of the alkalies in
conjunction with alkalies and with alkaline earths. My Invention differs there-
from in that I apply the oxidising agents herein-before mentioned to impure
or hard lead, the same being in a molten condition, not contained in a
furnace but in a crucible, melting pot, or other suitable apparatus or vessel,
and I operate on the molten metal immediately after it is tapped from the
smelting furnace, such smelting or reducing furnace being either a blast,
cupola, or reverberatory furnace.
In witness whereof, I, the said William Baker, have hereunto set my
hand and seal, this Fourth day of December, One thousand eight
hundred and sixty.
WILLIAM BAKER. (L.S.)