IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD PIGMENT
Year: 1880

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltino, Lake,
& Co., Patent Agents, Southampton Buildings, London, for an Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD PIGMENT." A
communication from abroad by George T. Lewis, of Philadelphia, Pennsylvania,
United States of America.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at the
Office of the Commissioners of Patents on the 18th February 1880.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent
Agents, Southampton Buildings, London. "IMPROVEMENTS IN THE MANUFACTURE
OF WHITE LEAD PIGMENT." [A communication from abroad by George T. Lewis,
of Philadelphia, Pennsylvania, United States of America.]
In carrying this Invention into practice I pass fumes from lead ores, or waste
lead fumes from lead smelting or refining operations, or pulverized lead ore, over a
fire into a generator flame or through a heated retort, which purifies the fumes and
refines them, so that when they are passed through the cooling pipes and are caught
in the bags of textile fabric they are very pure and white.
When powdered galena or other sulphuretted lead ore is used for the manufacture
of white pigment I throw it over a coal fire or into a gas generator flame, or it is
thrown or blown by hot or cold blast into a retort, or muffle heated to redness.
The latter is preferable, because in the two former cases the carbonic oxide gas and
carbonic acid gas produced from the combustion of the carbonaceous fuel become
mixed with the lead fumes and entering the catching apparatus described in the
Specification of former Letters Patent, No. 687, dated the Twentieth day of February,
A.D. 1879, render the atmosphere about the bags very poisonous.
A white pigment can also be made by exposing coarse or crushed galena to the
joint action of heat and air in a kind of muffle furnace, excluding the poisonous
gas from the combustion of the fuel, but this is more expensive, and the galena when
crushed does not burn but melts, and is then volatilized. Although any of these
processes will serve when powdered galena or other sulphuretted lead ore is used I
prefer a retort or muffle, which is heated externally, and into which the pulverized
lead ore is thrown or blown, and the resulting fumes being collected in the cooling
and catching apparatus hereinbeforo mentioned.

page_text: The retort
I employ for this process an ordinary blower, and situated on one side of the
blower is a hopper, over which is a vibrated screen. Pulverized galena is thrown
upon the screen and passes into the hopper, from which it is drawn intimately
mixed with air, and blown into a retort or muffle by means of Luyeres.
has a lead bottom, and is heated externally by any convenient means; it may be
heated by gas. The pulverized galena mixed with air in passing through the red
hot retort is sublimed, and the fumes pass out by a flue into the cooling and catching
apparatus. When blown into a heated retort pulverized galena is sublimed at a
low temperature, while crushed galena is not.
When roasted sulphuretted lead ore has been used, or any oxidized lead ore, like
carbonate of lead, or a mixture of much oxidized lead ore with sulphuretted lead
ore, the crude lead fumes may be refined before reaching the catching apparatus by
passing them over or through a second fire which does not smoke, or by burning
generator gas in the flues of a furnace leading from the smelting furnace to the
cooling and catching apparatus.
This method cannot be used when sulphuretted ore alone is sinelted, since in this
case only lead, amounting to from 10 to 15 per cent. of the lead in the ore, passes
off as fumes, while nearly all the sulphur passes off, and the lead fumes will then
be mixed with gases containing a considerable amount of sulphurous acid gas, much
more than can combine with the lead, and this sulphurous acid, in passing over the
second fire in company with the fumes in an oxydizing atmosphere, is converted to
a great extent into sulphuric acid by the moisture in the blast of said fire, or from
combustion of hydrogen or hydro-carbons produced in said fire, sufficient in quantity
in a very short space of time to destroy the textile fabric in which the fumes are
collected, besides making the pigment unfit for use without washing.
I have however found that by passing the air blast for the refining fire over burnt
lime, or other suitable material for extracting the moisture, that the formation of
sulphuric acid was prevented when hard-coal, coke, charcoal, or gas fire of hydro-
Carbons were used.
Although the foregoing process is practicable, yet I prefer to pass the waste fumes
from the sulphuretted lead oro through a clay or cast iron retort heated to redness
by external heat before reaching the aforesaid cooling and catching apparatus,
because in this process no water is brought in contact with the fumes and sulphurous
acid to produce sulphuric acid. In this case any kind of fuel may be used, hence it
is the most desirable process, and since the gases from the fire do not enter the
catching apparatus the atmosphere around the bags is not so poisonous as is other-
wise the case.
Even with non-sulphuretted lead ore this process is desirable, since
the fire is open and easily managed.
When white lead pigment is manufactured from galena or other lead ores in a
raw or roasted state by subjecting them to the joint action of heat and air, either
with or without reducing means, according to the quality of the lead ore used, the
fumes are discoloured by particles of carbon or sulphuret of lead, or both, if the
greatest care is not taken in keeping a bright fire in the furnace. It has been found
that by passing these fumes, after they leave the furnaces where they are formed,
over a bright clear fire, or through a furnace in which generator gas is burned, the
dark and black particles are all burned out and the fumes are refined, and after
passing through the cooling pipes they are caught in tho bags of textile fabric, and
will be in the form of a white powder.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Robert Lako in the Great Soal Patent Office on the 18th
August 1880.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent
Agents, Southampton Buildings, London. "IMPROVEMENTS IN THE MANUFACTURE
OF WHITE-LEAD PIGMENT." A communication from abroad by George T. Lewis,
of Philadelphia, Pennsylvania, United States of America.
My Invention consists in passing fumes from lead-ores or waste lead-fumes from
lead smelting or refining operations, or pulverized lead-orc, over a fire into a
generator flame, or through a heated retort which purifies the fumes and refines
them, so that when they are passed through the cooling pipes and are caught in the
bags of textile fabric they are very pure and white.
When powdered galena or other sulphuretted lead ore is used for the manufacture
of white pigment I throw it over a coal fire or into a flame of generator-gas, or it is
thrown or blown by hot or cold blast into a retort, or muffle heated to redness.
The latter is preferable, because in the two former cases the carbonic oxide gas and
carbonic acid gas produced from the combustion of the carbonaceous fuel become
mixed with the lead fumes, and enter the catching apparatus described in the
Specification of former Letters Patent, No. 687, A.D. 1879, rendering the atmosphere
about the bags very poisonous. A white pigment can also be made by exposing
coarse or crushed galena to the joint action of heat and air in a kind of muffle
furnace, excluding the poisonous gas produced by the combustion of the fuel from
contact with the volatilized fumes in the retort or muffle; but this is more expen-
sive, and the galena when crushed does not burn but melts, and is then volatilized.
Although any of these processes will serve when powdered galena or other
sulphuretted lead ore is used, I prefer a retort or muffle which is heated externally,
and into which the pulverized lead-ore is thrown or blown, the resulting fumes
being collected in the cooling and catching apparatus herein before referred to.
A furnace suitable for the purpose of this Invention is illustrated in Figures 1
and 2 of the Drawing, in which,―
Figure 1 is an elevation partly in section of the furnace and blowing apparatus,
and
Figure 2 is a plan partly in horizontal section of the same.
The remaining Figures are heroinafter referred to.
A is an ordinary blower, on one side of which is a hopper B, over which is a
vibrating screen C. Pulverized galena is thrown upon this screen C and passes into
the hopper B, from which it is drawn intimately mixed with air, and blown into
the retort or muffle F through the tnyeres E. The retort F has a lead bottom, and
is heated externally by any convenient means; in the Drawing it is shewn as con-
structed to be heated by gas. The pulverized galena mixed with air in passing
through the red hot retort is sublimed, and the fumes pass out by the flue G into
the cooling and catching apparatus. When blown into a heated retort pulverized
galena is sublimed at a low temperature, while crushed galona is not.
When roasted sulphuretted lead-ore has been used, or any oxidized lead-ore liko
carbonate of lead, or a mixture of such oxidized lead-oro with sulphuretted lead ore,
the crude lead fumes may be refined before reaching the catching apparatus by
passing them over or through a second fire which does not smoke, or by burning
generator-gas in the flues of a furnace leading from the smelting furnace to the
cooling and catching apparatus.
This method cannot be used when sulphuretted ore alone is smelted, since in this
case only lead amounting to from 10 to 15 per cent. of the lead in the ore passes off
as fumes, while nearly all of the sulphur passes off, and the lead fumes will then be

page_text: mixed with gases containing a considerable amount of sulphurous acid gas, much more
than can combine with the lead, and this sulphurous acid, in passing over the second
fire in company with the fumes in an oxidizing atmosphere, is converted to a great
extent into sulphuric acid by the moisture in the blast of said fire, or from combus-
tion of hydrogen or hydro-carbons produced in the said fire, sufficient in quantity
in a very short space of time to destroy the textile fabric in which the fumes are
collected, besides making the pigment unfit for use without washing.
It has however been found that by passing the air blast for the refining fire over
burnt lime, or other suitable material for extracting the moisture, the forination of
sulphuric acid was prevented when hard coal, coke, charcoal, or gas fire of hydro-
carbons were used.
Although the foregoing process is practicable, yet I prefer to pass the waste
fumes from the sulphuretted lead ore through a clay or cast iron retort heated to
redness by external heat before reaching the aforesaid cooling and catching
apparatus, because in this process no water is brought in contact with the fumes
and sulphurous acid to produce sulphuric acid. In this case any kind of fuel may
be used, hence it is tho most desirable process; and since the gases from the fire do
not enter the catching apparatus the atmosphere around the bags is not so poisonous
as is otherwise the case. Even with non-sulphuretted lead ore this process is
desirable, since the fire is open and easily managed.
Figure 3 represents partly in section and partly in elevation the devices or means
employed for working this process.
In this Figure H represents the Scotch hearth in which the ore is smelted, and
from which the fumes pass through the clay retort I, which is heated externally by
a fire. From this retort they pass through the cooling pipes J, through which they
are drawn by the suction-fan K, and by which they are forced into the catching
apparatus L.
When white lead pigment is manufactured from galena or other lead ores in a
raw or roasted state by subjecting them to the joint action of heat and air, either
with or without reducing means, according to the quality of the lead ore used, the
fumes are discolored by particles of carbon or sulphuret of lead, or both, if the
greatest care is not taken in keeping a bright fire in the furnace. It has been
found that by passing these fumes, after they leave the furnace where they are
formed, over a bright clear fire, or through a furnace in which generator-gas is
burned, the dark and black particles are all burned out and the fumes are refined,
and after passing through the cooling pipes they are caught in the bags of textile
fabric, and will be in the form of a white powder.
Figure 4 of the Drawing represents devices for carrying this process into
practice.
M is a Scotch hearth where the fumes are produced; from this hearth they pass
into the furnace N, which is heated by a flame of generator-gas which burns out all
the impurities contained in the incoming fumes and purifies the latter, and the
purified white lead fumes then pass through the cooling pipes O and are blown into
the catching or screening apparatus P.
I prefer to use a generator gas flame by reason of its uniformity of composition
and easy management.
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 refining waste lead fumes from smelting furnaces by
passing the waste fumes through tubes or retorts heated externally and before
collecting the said fumes, substantially as above described.
Second. The process of making white pigment by passing powdered galena or
other sulphuretted lead ore intimately mixed with air through a retort or muffle
heated externally, and collecting the resulting fumes by means of collecting and
catching apparatus, substantially as above described,

page_text: Third. The refining of lead fumes from lead-fume-furnaces, or waste lead fumes
from the smelting of oxidized lead or roasted sulphuretted lead-ores, by passing
these fumes over or into a second fire before they reach the cooling and catching
apparatus, substantially as above set forth.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Eighteenth day of August, in the year of our Lord One
thousand eight hundred and eighty.
W. ROBT. LAKE. (L.S.)