IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD
Year: 1879

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake, & Co.,
Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD." A communication
from abroad by George T. Lewis, of Philadelphia, Pennsylvania, United States
of America.
aled the 23rd March 1880, and dated the 30th September 1879
PROVISIONAL SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 30th September 1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN THE MANUFACTURE OF
WHITE LEAD." [A communication from abroad by George T. Lewis, of
Philadelphia, Pennsylvania, United States of America.]
Heretofore the manufacture of dry white lead from galena or the native sul-
phurets has been effected by roasting or desulphurizing the galona, and then mixing
the residue after roasting with carbon, and subjecting the mixture to the action of
heat in a compound reducing or subliming and oxidizing furnace, and collecting the
resulting fumes in textile bags. But this Invention is based on the discovery that
by subliming the native or raw sulphuret of lead, and then oxidizing the volatile
products and cooling the fumes, and collecting them by means of textile fabric, a
superior basis of a pigment can be obtained. The admixture of carbon with the
raw ore will facilitate the subliming process, or it may be carried on in a muffle or
reverberatory furnace without the previous admixture of carbon.
The furnace, which has been found to work well for the purposes above mentioned,
is commonly known as the "Wetherill furnace."
This furnace has a main chamber, the bottom of which is composed of iron bars
perforated with small holes, and preferably made slightly conical with the larger
diameter downward. The size of the holes would be such as to prevent the escape
of the crushed ore and coal. These perforated bars are suitably sustained at the
ends on the front and back walls. The ash pit below the perforated bottom is of
equal area therewith, and is provided with a door in front and with a hole at the
back for the reception of a pipe from suitable blowing apparatus.

page_text: The walls and arch on the top should be built of some refractory substance, such
as firebrick.
The front is entirely open, and provided with sliding doors, by which it can be
closed when working and opened to remove the residuum.
At the back there are two slides to give access to the main chamber for stirring
the charge and for inspection. At the back, near the arch, there is a hole governed
by a sliding damper leading to a chimney for carrying off smoke and impure gases
in the beginning of the operation on a new charge.
In the centre of the roof there is an aperture governed by a damper or sliding
door leading to a suitable apparatus for the collection of the oxidized vapors of
lead.
The exterior walls may be built up to form two feeding troughs, one on each
side of the arch or roof, and provided each with an aperture or passage leading to
the inside or main chamber, and each aperture or passage is provided with a cover
to be put on after the furnace has been charged.
In working with this furnace crushed ore (native sulphuret of lead) and carbon,
preferably in the state of pea or dust, anthracite coal are mixed in the proportion
of half and half, the mixture is ignited, and the fumes are oxidized by the blast
through the mixture, which also promotes the combustion.
Dense white vapors or fumes pass off, and are conveyed to a separate chamber,
where they are strained by passing through a screen or series of screens of muslin
or other textile fabric. Lime may also be employed in the furnace in the propor-
tion of two hundred pounds of lime to four hundred pounds of galena, although the
addition of the lime is not necessary in all cases.
Instead of this furnace a muffle furnace may be employed, in which the heat is
applied indirectly to the ore with the precaution of constructing the sole or bottom
of this furnace of a material not rapidly acted on by the constituents of the ore, or a
reverberatory furnace may be used, in which the heat is directly applied. In both
of these two cases reducing carbon may or may not be mixed with the ore.
Generated gas can be used in place of coal to accomplish the same end.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Robert Lake in the Great Seal Patent Office on the 27th
March 1880.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN THE MANUFACTURE OF
WHITE LEAD." A communication from abroad by George T. Lewis, of
Philadelphia, Pennsylvania, United States of America.
Heretofore the manufacture of dry white lead from galena or the native sul-
phurets has been effected by rosting or desulphurizing the galena, and then mixing
the residue, after roasting, with carbon and subjecting the mixture to the action of
heat in a compound reducing or subliming and oxidizing furnace, and collecting the
resulting fumes in textile bags.
This Invention however is based upon the discovery that by subliming unroasted
galena, or the native, or raw sulphuret of lead, and then oxidizing the volatile
products, cooling the fumes, and collecting them by means of a textile fabric, a
superior basis of a pigment can be obtained. The admixture of carbon with the
raw ore will facilitate the subliming process, or it may be carried on in a muffle or
reverberatory furnace without the previous admixture of carbon.
The furnace, which has been found to answer well for the purposes above
mentioned, is commonly known as the "Wetherill furnace," and is represented
in the accompanying Drawing, in which
Figure 1 is a plan of the said furnace, and
Figures 2 and 3 are front and rear elevations of the same.
Figure 4 is a central longitudinal section of the said furnace.
a represents the main chamber, the bottom b of which is composed of iron bars
perforated with small holes of about one quarter of an inch in diameter and about
one inch apart, and preferably made slightly conical, with the larger diameter
downward, that is to say, the said holes are of such a size as to prevent the escape
of the crushed ore and coal. These perforated bars are suitably sustained at the
ends on the front and back walls of the furnace. The ash pit below the perforated
bottom is of equal area therewith, and is provided with a door e in front and with
a hole fat the back for the reception of a pipe from suitable blowing apparatus.
The walls g, g, and arch on the top should be built of some refractory substance,
such as fire brick.
The front of the furnace is entirely open, and is provided with sliding doors i, by
which it can be closed when working and opened to remove the residuum.
At the back of the furnace there are two slides j, j, to permit access to the main
chamber for stirring the charge and for inspection.
At the back, near the arch, there is a hole k, governed by a sliding damper
leading to a chimney, for carrying off smoke and impure gases at the commence-
ment of the operation upon a new charge.
In the centre of the roof there is an aperture l, governed by a damper or sliding
door m³, the said aperture leading to a suitable apparatus for the collection of the
oxidized vapors of lead.
The exterior walls n, o, p, q, may be built up to form two feeding troughs r, 1,
one on each side of the arch or roof, and each provided with an aperture or
passage 8 communicating with the inside or main chamber, and each aperture or
passage is provided with a cover to be put on after the furnace has been charged.
In working with this furnace crushed ore (native sulphuret of lead) and carbon,
preferably in the state of pea or dust anthracite coal, are mixed in equal propor-
tions, the mixture is ignited and the fumes are oxidized by the blast through the
mixture, which also promotes the combustion. Dense white vapors or fumes pass
off, and are conveyed to a separate chamber, where they are strained by passing

page_text: through a screen or series of screens of muslin or other textile fabric. Lime may
also be employed in the furnace in the proportion of two hundred pounds of lime
to four hundred pounds of galena, although the addition of the lime is not necessary
in all cases.
Instead of the furnace above described a nuffle furnace may be employed, in
which the heat is applied indirectly to the ore, with the precaution of constructing
the sole or bottom of this furnace of a material not rapidly acted on by the con-
stituents of the ore, or a reverberatory furnace may be used in which the heat is
directly applied. In both of these two cases reducing carbon may or may not be
mixed with the ore.
I sometimes employ generated gas in place of coal to effect the same result.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,-
-
First. The process of manufacturing the basis of a pigment by subliming unroasted
galena (uative sulphuret of lead) oxidizing the volatile products, and then collecting
the fumes so produced as above described.
Second. The production of the sublimed and oxidized fumes of raw galena for
the purpose specified.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Twenty-seventh day of March, in the year of our
Lord One thousand sight hundred and eighty