IMPROVEMENTS IN MANUFACTURE AND TREATMENT OF WHITE LEAD, AND IN APPARATUS CONNECTED THEREWITH
Year: 1867

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, for the Invention of "IMPROVEMENTS IN
MANUFACTURE AND TREATMENT OF WHITE LEAD, AND IN APPARATUS CONNECTED
THEREWITH." A communication from abroad by Robert Griffith Hat-
field, of New York City, in the United States of America.
Sealed the 1st November 1867, and dated the 12th June 1867.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents, with his Petition, on the
12th June 1867.
1, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, do hereby declare the nature of the said Invention for "IMPROVE.
MENTS IN THE MANUFACTURE AND TREATMENT OF WHITE LEAD, AND IN APPARATUS
CONNECTED THEREWITH," to be as follows:-
The first part of the Invention relates to a process for the manufacture of
white lead from metallic lead in which converting chambers are employed.
The converting chambers may be made of any suitable material, form, and
capacity according to the extent of the proposed operations, but for con-
venience I prefer that they shall be constructed in rectangular form, say,
from 12 to 20 feet square on the ground plan, and 20 to 30 feet high. A
Price 8d1

page_text: converting chamber is built of strong frames, and double walled or boarded
inside and out of the framing, with tongued and grooved boards secured by
blind nailing in such a manner that no iron shall be exposed on the interior
surface of the chamber, and when closed the chamber shall be air-tight.
Between the inner and outer walls of the top, bottom, and sides the framing
will be filled, like the walls of an ice house, with charcoal, tan bark, sawdust,
or any other suitable non-conducting substance which shall effectually shut
out the influence of the atmosphere upon the internal temperature of the
converting chamber so that there shall be no disturbing agency during the
process of conversion by changes of temperature. The bottom of the chamber
is made in the form of a hopper leading down by a spout to a cylindrical
revolving screen of coarse wire placed in a tub or vat. A sliding valve may
be used to close the spout when desired; four or more posts are set up
vertically in the chamber to divide it into sections for supporting sliding trays
or shelves which carry the metallic lead piled up in scales or spangles with
spaces between. The trays are made of slats or fine latticework frames to
hold the scales or spangles of metallic lead and allow the powdered carbonates
as they form and are shaken off to fall down through to the bottom into the
hopper. The trays are made very strong to sustain heavy weights of metal.
The front side of the converting chamber is made with sliding or swinging
doors to open for introducing the trays and handling them occasionally to
shake down the powdered carbonates as they form. In the lower part of the
chamber is placed a horizontal series of return steam pipes for heating the
interior, they are made of block tin, or tinned iron, or any other suitable
material. When the chamber has been charged with trays loaded with the
lead the process of corrosion may be begun. For this purpose a force pump is
placed in a reservoir for containing water and acetic acid, or other liquids used
in the process, and the pump is connected by a main pipewithsmall branchpipes
that are introduced into the back part of the chamber at such heights and
distances apart as to pass above and between the trays loaded with lead as
may be necessary to sprinkle the lead with a fine spray of water or dilute
acetic acid, forced through capillary or fiue holes in the branch pipes. The
branch pipes are provided with stop cocks outside of the converting chamber,
and they extend across it from the back to the front part. The interior of
the chamber is to be heated by the steam pipes to a temperature varying
from 100 to 120 degrees Fahrenheit.
The first operation in the process of conversion is to wet the metallic lead
on the trays with either pure water or water slightly acidulated with acetic
acid; this is done by means of the force pump through the main and branch

page_text: pipes, by which a fine spray or mist is thrown directly upon the surface of
the lead until the whole mass is thoroughly moistened. The contents of the
reservoir are raised to the same temperature as that of the converting chamber
by means of a steam pipe leading into the reservoir. After the lead has been
properly wetted with water or acidulated water it is allowed to stand until
a thin film of oxide has formed on the surface of the metal.
When a coating
of oxide has formed on the metal, dilute acetic acid is then introduced into
the reservoir and forced by the pump, as before described, through the pipes
upon the lead on the trays to moisten it well; the low oxide of lead previously
formed is thus converted into an acetate of lead which is the second stage in
the process of conversion.
The next part of the process consists in the introduction of carbonic acid
to convert the acetate of lead into a carbonate. This is accomplished by
carrying carbonic acid gas into the converting chamber from a charcoal
furnace connected with it by a pipe leading to the middle of the top from a
gas receiving vessel. The furnace is provided with a draft flue aud also a
pipe leading to the receiving vessel, both pipes lead from a common fire
chamber behind the furnace, and both are provided with dampers or slide
valves for regulating the flow of carbonic acid gas into the converting chamber.
When the charcoal fire is first started the valve in the draft flue is opened and
the valve in the pipe of receiving vessel is closed to prevent any access
of dust or dirt from the fire into the chamber, and when the charcoal is
thoroughly ignited the valve is opened, after all sulphurous or tarry matters
have passed into the chimney, and the draft valve is closed to lead the pure
carbonic acid gas into the receiving vessel as desired. The converting
chamber is filled with the gas through the supply pipe at the top until fully
charged, and the acetate of lead is converted by the action of the carbonic
acid into a carbonate of lead. The carb mic acid gas is maintained in the
chamber under pressure by rarification by means of the steam heating pipes,
but a force pump or any other convenient manner or means may be employed
to produce a pressure of carbonic acid gas within the chamber in order to
expedite its intimate combination with the acetate of lead. The supply pipe
is provided with a valve at its connection on the top of the converting
chamber, or a stop cock to admit or shut off the gas as required. From time
to time during the operation the loaded trays are agitated so that the particles
of carbonate of lead formed by the combination of carbonic acid with the
acetate of lead shall fall into the hopper at the bottom of the chamber and a
continuous series of operations is maintained by introducing the prepared
metal and taking out simultaneously the converted lead.

page_text: The three several distinct operations thus described in the foregoing process
are repeated and continued until the metallic lead in the chamber is con-
verted into a carbonate, beginuing first with the thorough moisture of the
scale lead on the trays by a spray from the pipes of pure water or slightly
acidulated water to oxidize the metallic lead, next by the same means further
moistening the oxidized metal with dilute acetic acid to form an acetate of
lead, and finally charging the chamber with carbonic acid gas under pressure.
During the latter part of the process I occasionally introduce chlorine into
the chamber by injecting warm chlorinated water through the pump. The
chlorine acts upon and decomposes and bleaches any accidental organic
matter that may be present in the chambers; the chlorine also unites with
theacetic acid to form chlor-acetic acid and ultimately oxalicacidall possessing
bleaching as well as docomposing qualities and all yielding their products to
the carbonic acid gas and resulting in carbonate of lead. The lead products
which fall into the hopper pass thence into the tub through the revolving
screen below, which sifts and separates them from any coarse particles of
metallic lead which may fall into the hopper. The products are taken up by
an elevator from the vat or tub and conveyed into the first of a series of
separating or washing vats or settling tubs arranged one above another and
managed in the ordinary way for float washing. The first settling tub of
the series is provided with a false perforated bottom or screen for catching
coarse particles of the imperfectly corroded lead placed between a double set
of stirrers above and below, and each of the vats or settling tubs is also
provided with stirrers and with wire screens successively finer in their mesh,
and also with faucets for separating the coarser from the finer material until
the process of separation is completed.
The lead products are then ready for the process of finishing in the finishing
apparatus, as described in the second and fourth parts of this Invention, in
which the said products are warmed to a temperature about equal to that of
the converting chamber. The products are now stirred and treated with
chlorine if further bleaching is needed, and with carbonic acid gas under
pressure or without pressure until all the particles are brought into uniform
condition as a true carbonate of lead; after this the products are transferred
to the ordinary drying tables, dried, and put up for market. Toassist the proper
observance of the process of conversion at all times glass windows are set in
the back and front sides of the converting chamber in such positions as
command a view of all parts of the interior. The attendants can thus ascertain
what is required in the various stages of the process in order that it shall be
managed with regularity and dispatch, and that the product shall be uniform

page_text: in character. The chamber is as nearly air-tight as possible when closed, but
as air, heat, and moisture are all necessary for the oxidation of the metallic
lead, provision is duly made for their introduction as herein-before described.
For the admission of sufficient air in all parts of the chamber during the
early stage of the process when the metal is to be converted into an oxide as
described, after moistening it with pure water or slightly acidulated water,
draft holes having sliding valves are placed near the four corners on the top
and the back and front sides of the chamber. The current of air through
the chambers can be regulated in its course to operate on the lead in different
parts by opening and closing the draft holes above and below on the same or
opposite sides and corners as desired and thus control the process of oxidation
to make it complete and uniform in every way of the converting chamber.
The temperature of the converting chamber is always maintained at from 100
to 130 degrees Fahrenheit, the requisite moisture for oxidation being supplied
by a fine spray as described in quantities to keep the metal at the due point.
By introducing the carbonic acid gas into the converting chamber from above,
and by its expansion under the influence of heat, a pressure of the gas is
produced which causes it to penetrate every part of the interior of the chamber
and enter the smallest interstices between the lead flakes and attack all the
material under treatment. The supply of carbon is thus ample for converting
the acetate of lead into a true amorphous carbonate, there is no waste of
material in any part of the process, as even the refuse formed in casting the
lead into proper shape, known as dross, is available, and may be converted
into carbonate of lead on being passed through the converting chamber in the
same manner as before described for pure metallic lead, in fact the dross is
already a low oxide well adapted to treatment in the converting chamber as
"efore described for the first stage of the process.
The second part of the Invention relates to the finishing and improvement
of the ordinary white leads of commerce, and which contain portions of the
oxide and acetate of lead, and sometimes particles of metallic lead; and this
Invention consists in subjecting amass of the said white lead, mixed with water
and heated to the action of a volume of carbonic acid gas in the manner
fully described hereafter, whereby the said mass is converted into pure
carbonate of lead. The ordinary white lead of commerce is produced by the
action upon metallic lead of heat, moisture, the vapor of vinegar, and carbonic
acid gas.
In thisprocess, however, theconditions are seldom sofavorable that the entire
mass of metallic lead is converted into a pure carbonate of lead, the resulting
material, although mainly a carbonate, containing oxide and acetate of lead.

page_text: In order to reduce the material thus obtained to a pure carbonate of lead
I make use of the apparatus described in the fourth part of the Invention. I
introduce the material into a suitable vessel and add water until the mass is in
a pasty condition. A stirrer revolves in the vessel and carries a number of
arms or blades, the action of which maintains the mass at a uniform consistency.
The material in the vessel is then washed with water several times in order
to remove the superfluous portion of acetate of lead which may be mixed
with the mass, and the latter is then heated to and maintained at a temperature
of from 100 to 130 degrees Fahrenheit by means of a jet of steam introduced
through a pipe which extends nearly to the bottom of the vessel. When the
entire mixture is at the proper temperature carbonic acid gas is forced through
a pipe into the mass of the material until the latter is converted into a pure
carbonate of lead; during this process the mass is frequently examined and
may be treated with a solution of chlorine when desired to decompose
impurities and improve the color of the material.
The lead products obtained in the manner described in the first and third
parts of the Invention, may be also treated and finished substantially as set
forth in the second part of the Invention, after which the products are
transformed to the ordinary drying tables, dried, and put up for market. By
this means the condition of the lead when dried is such that it does not
require grinding to produce uniformity and fineness in quality, as it is already
an impalpable powder.
The third part of the Invention relates to the manufacture of white lead
or carbonate of lead from lead ores or minerals containing carbonate of lead
without reducing the said ores or minerals by fire. To accomplish this
purpose the native carbonates or lead ores are crushed and washed thoroughly
with chlor-acetic acid largely diluted with water and then ground in water
into an impalpable powder, during which operation the greater bulk of the
impurities are washed away and the carbonates settle in the vessel, the water
is to be heated from 100 to 140 degrees Fahrenheit.
The whole mass thus prepared is now treated in the apparatus described
in the third part of the Invention with chlor-acetic acid for the purpose of
discharging the coloring matter and decomposing all accidental impurities.
The chlorine and acetic acid form oxalic acid, thus subjecting the mass to the
best reducing and bleaching agents. After this carbonic acid gas is applied
to the mass under pressure and a stream of carbonic acid gas is passed through
the mass until all its particles are converted into a true carbonate; should
copper or cobalt be present they are to be extracted by the application of
ammonia water in the place of chlorine.

page_text: The fourth part of the Invention relates to an apparatus for finishing and
purifying the lead products by washing and treating them with acids and
gases. For this purpose I use the vessel before described as containing a
rotary stirrer; when gases or other substances are to be applied under pressure
the mouth of the vessel is closed by a cover which is divided into two parts
drawn together by screw bolts, the edges of the parts are provided with claws
which catch over the upper lip of the vessel. The shaft of the stirrer is
girdled by a stuffing box, apertures are made provided with valves for the
admission and withdrawal of the contents; pipes also pass through the cover
and enter the body of the vessel, these pipes are intended for the admission
of steam, acid solutions, gas, or other substances or chemicals it is desired to
introduce.
The lead products obtained as described in the first, second, and third parts
of the Invention are placed in the vessel, warmed, stirred, and treated with
solutions and gases as herein-before described. The solutions and gases may
be introduced through one of the pipes which are intended to communicate
with a force pump or other suitable medium for supporting the required
degree of pressure.
According to the fifth part of the Invention the metallic lead is prepared
or formed properly for piling upon the shelves with wide spaces or interstices
between them by means of an iron wheel which receives the molten metal
from a melting pot and throws it by its paddles on which the metal drops
with great force against a flat iron shield set up in front of the wheel. The
wheel is revolved with great velocity and throws the melted lead against the
iron shield to flatten it in irregular shapes or spangles which present a great
amount of corroding surface and lie loosely together when piled.
SPECIFICATION in pursuance of the conditions of the Letters l'atent, filed
by the said Alexander Melville Clark in the Great Seal Patent Office
on the 9th December 1867.
TO ALL TO WHOM THESE FRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex, send
greeting.
WHEREAS Her inost Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twelfth day of June, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirtieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said

page_text: Alexander Melville Clark, Her special licence that I, the said Alexander
Melville Clark, my executors, administrators, and assigns, or such others as
I, the said Alexander Melville Clark, my 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 THE MANUFACTURE AND TREATMENT OF WHITE
LEAD, AND IN APPARATUS CONNECTED THEREWITH," a communication to me from
abroad by Robert Griffith Hatfield, of New York City, in the United States
of America, upon the condition (amongst others) that I, the said Alexander
Melville Clark, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, 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 Alexander Meville Clark, 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, reference being had to the Sheet of Drawings hereunto
annexed, and to the letters and figures marked thereon, (that is to say):-
The first part of this Invention relates to the mauufacture of white lead
from metallic lead.
The second part of this Invention relates to the finishing and improvement
of the ordinary white lead of commerce.
The third part of this Invention relates to the manufacture of white lead
from lead ores and minerals containing carbonate of lead.
The fourth part of this Invention relates to an apparatus for washing lead
products and treating them with solutions and gases and finishing them.
The fifth part of this Invention relates to an apparatus for suitably pre-
paring the metallic lead for treatment according to these improvements.
I have denominated this Invention an improvement in the manufacture of
the pigment known in commerce as white lead, the actual resultant or article
produced by means of the improvements being a pure or nearly pure carbonate
of lead.
Referring to the Drawings, Figure 1 represents a vertical sectional view of
the improved converting chamber and its connections for the supply of carbonic
acid from a charcoal furnace, and for conveying the converted lead into the

page_text: washing apparatus. Figure 2 represents a series of washing vats or tubs.
Figure 3 is a horizontal section of the converting chamber taken in the line
x, x, showing a series of return steam pipes for heating the interior of the
converting chamber. Figure 4 is a horizontal section of the same taken in
the line y, y, with the heating pipe and lower set of shelves removed showing
the hopper in the bottom of the chamber. Figure 5 is a top or plan view of
the converting chamber. Figure 6 is a partial vertical sectional view of the
converting chamber showing the arrangement of pipes for conveying water,
acetic acid, and chlorine, and the sprinkling thereof upon the metallic lead in
the form of fine spray. Figure 7 represents a melting pot and an apparatus
connected therewith for separating the metallic lead into flakes, spangles, or
irregular scales. Figure 8 is a plan view of a washing, finishing, and converting
apparatus; Figure 9 is a side sectional elevation of the same. Similar letters
of reference indicate corresponding parts in the various Figures.
The first part of the Invention relates to a process for the manufacture of
white lead from metallic lead in which converting chambers are employed.
The converting chambers may be made of any suitable material, form, and
capacity, accordingto theextent of theproposedoperations; but forconvenience
I prefer that they shall be constructed in rectangular form, say from 12 to 20
feet square on the ground plan, and 20 to 30 feet high. A converting chamber
is built of strong frames, and double walled or boarded inside and out of the
framing with tongued and grooved boards secured by blind nailing in such a
manner that no iron shall be exposed on the interior surface of the chamber,
and when closed the chamber shall be air-tight. Between the inner and
outer walls of the top, bottom, and sides the framing will be filled like the walls
of an ice house with charcoal, tan bark, sawdust, or any other suitable non-
conducting substance, which shall effectually shut out the influence of the
atmosphere upon the internal temperature of the converting chamber, so that
there shall be no disturbing agency during the process of conversion by
changes of temperature.
In the Drawings a, a, represent the side walls of the converting chamber,
a¹ the front, and a² the back, as the filling of charcoal or other non-con-
ducting substance, b the top, and c the bottom. The bottom c of the
chamber is made in the form of a hopper, leading down by a spout d to a
cylindrical revolving screen A of coarse wire placed in a tub or vat B; a
sliding valve d¹ may be used to close the spout d when desired. Four or more
posts e, e, are set up vertically in the chamber to divide it into sections for
supporting sliding trays or shelves e¹ which carry the metallic lead piled up in
scales or spangles with spaces between as shown on one tray e¹ in Figure 1.
اكد

page_text: The trays el are made of slats or fine latticework frames to hold the scales or
spangles of metallic lead, and allow the powdered carbonates as they form and
are shaken off to fall down through to the bottom into the hopper d; the
trays are made
every strong to sustain heavy weights of metal. The front side
a¹ of the converting chamber is made with sliding or swinging doors to open
for introducing the trays and handling them occasionally to shake down the
powdered carbonates as they form. In the lower part of the chamber is
placed a horizontal series of return steam pipes g, g, for heating the interior
they are made of block tin, or tinned iron, or any other suitable material; when
the chamber has been charged with trays loaded with the lead the process of
corrosion may be begun. For this purpose a force pump F is placed in a
reservoir G for containing water and acetic acid or other liquids used in the
process, and the pump is connected by a main pipe h with small branch pipes
,, that are introduced into the back part of the chamber at such heights
and distances apart as to pass above and between the trays loaded with lead
as may be necessary to sprinkle the lead with a fine spray of water or dilute
acetic acid forced through capillary or fine holes in the branch pipes as shown
in Figure 6, and herein-after described. The branch pipes k, k, are provided
with stopcocks 1,1, outside of the converting chamber, and they extend across
it from the back to the front part. The interior of the chamber is to be
heated by the steam pipes to a temperature varying from 100 to 130 degrees
Fahrenheit.
The first operation in the process of conversion is to wet the metallic
lead on the trays with either pure water or water slightly acidulated with
acetic acid. This is done by means of the force pump through the main
and branch pipes by which a fine spray or mist is thrown directly upon the
surface of the lead until the whole mass is thoroughly moistened. The contents
of the reservoir G are raised to the same temperature as that of the converting
chamber by means of a steam pipe leading into the reservoir. After the lead
has been properly wetted with water or acidulated water it is allowed to stand
until a thin film of oxide has formed on the surface of the metal.
When a
coating of oxide has formed on the metal dilute acetic acid is then introduced
into the reservoir G, and forced by the pump as before described through the
pipes k, k, upon the lead on the trays to moisten it well, the low oxide of
lead previously formed is thus converted into an acetate of lead which is the
second stage in the process of conversion.
The next part of the process consists in the introduction of carbonic
acid to convert the acetate of lead into a carbonate. This is accomplished
by carrying carbonic acid gas into the converting chamber from a

page_text: charcoal furnace H connected with it by a pipe m leading into the middle of
the top from a gas receiving vessel I. The furnace H is provided with a
draft flue m' and also a pipe m² leading to the receiving vessel I, both pipes
lead from a common fire chamber behind the furnace, and both are provided
with dampers or slide valves n, ni, for regulating the flow of carbonic
acid gas into the converting chamber. When the charcoal fire is first
started the valve n' is opened, and the valve n is closed to prevent any access
of dust or dirt from the fire into the chamber, and when the charcoal
is thoroughly ignited the valve n is opened after all sulphurous or tarry
matters have passed into the chimney, and the valve n' is closed to lead the
pure carbonic acid gas into the receiving vessel I as desired. The converting
chamber is filled with the gas from the top through the pipe m until fully
charged, and the acetate of lead is converted by the action of the carbonic
acid into a carbonate of lead. The carbonic acid gas is maintained in the
chamber under pressure by rarefaction by means of the steam heating pipes.
But a force or any other convenient manner or means may be employed
to produce a pressure of carbonic acid gas within the chamber in order to
expedite its intimate combination with the acetate of lead. The pipe m is
provided with a valve at its connection on the top of the converting chamber,
or a stop-cock m³ to admit or shut off the gas as required. From time to time
during the operation the loaded trays are agitated so that the particles of
carbonate of lead formed by the combination of carbonic acid with the acetate
of lead shall fall into the hopper at the bottom of the chamber, and a con-
tinuous series of operations is maintained by introducing the prepared meta
and taking out simultaneously the converted lead. The three several distinct
operations thus described in the foregoing process are repeated and continued
until the metallic lead in the chamber is converted into a carbonate, beginning
first with the thorough moisture of the scale lead on the trays by a spray from
the pipes of pure water or slightly acidulated water to oxidize the metallic
lead; next by the same means further moistening the oxidized metal with
dilute acetic acid to form au acetate of lead; and finally charging the chamber
with carbonic acid gas under pressure. During the latter part of the process I
occasionally introduce chlorine into the chamber by injecting warm chlorinated
water through the pump F. The chlorine acts upon and decomposes and
bleaches any accidental organic matter that may be present in the chambers;
the chlorine also unites with the acetic acid to form chlor-acetic acid, and
ultimately oxalic acid, all possessing bleaching as well asdecomposing qualities,
and all yielding their products to the carbonic acid gas and resulting in
carbonate of lead. The lead products which fall into the hopper d pass thence

page_text: into the tub B through the revolving screen A, which sifts and separates them
from any coarse particles of metallic lead which may fall into the hopper.
The products are taken up by the elevator J from the vat or tub B and
conveyed into the first of a series of separating or washing vats or settling
tubs K¹, K², K³, K4, arranged one above another and managed in the ordinary
way for float washing, as represented in Figure 2. The first settling tub of
the series is provided with a false perforated bottom or screen p for catching
coarse particles of the imperfectly corroded lead placed between a double
set of stirrers q, q, above and below, and each of the vats or settling tubs
are also provided with stirrers and with wire screens successively finer for
separating the coarser from the finer material until the process of separa-
tion is completed. The lead products are then ready for the
prccess of
finishing in the finishing apparatus as described in the second and fourth
parts of this Invention, in which the said products are warmed to a tem-
perature about equal to that of the converting chamber. The products are
now stirred and treated with chlorine, if further bleaching is needed, and
with carbonic acid gas under a pressure or without pressure until all the
particles are brought into uniform condition as a true carbonate of lead. After
this the products are transferred to the ordinary drying tables, dried, and put
for market. To assist the proper observance of the process of conversion
at all times glass windows are set in the back and front sides of the converting
chamber in such positions as command a view of all parts of the interior.
The attendants can thus ascertain what is required in the various stages of the
process in order that it shall be managed with regularity and dispatch, and
that the product shall be uniform in character. The chamber is as nearly
air-tight as possible when closed, but as air, heat, and moisture are all necessary
for the oxidation of the metallic lead provision is duly made for their introduc-
tion as herein-bofore explained. For the admission of sufficient air in all parts
of the chamber during the early stage of the process when the metal is to be
converted into an oxide as described, after moistening it with pure water or
slightly acidulated water draft holes s, s, having sliding valves are placed near
the four corners on the top and the back and front sides of the chamber.
The current of air through the chambers can be regulated in its course to
operate on the lead in different [arts by opening and closing the draft holes
above and below on the same or opposite sides and corners, as desired, and
thus control the process of oxidation to make it complete and uniform in every
part of the converting chamber. The temperature of the converting chamber
is always maintained at from 100 to 130 degrees Fahrenheit, and the
requisite moisture for oxidation being supplied by a fine spray, as described, in
up

page_text: quantities to keep the metal at the dne point. By introducing the carbonic
acid gas into the converting chamber from above, and by its expansion under
the influence of heat, a pressure of the gas is produced which causes it to
penetrate every part of the interior of the chamber and enter the smallest
interstices between the lead flakes and attack all the material under treatment.
The supply of carbon is thus ample for converting the acetate of lead into a
true amorphous carbonate. In this process there is no waste of material in
any part of the process, as even the refuse formed in casting the lead into
proper shape, known as dross, is available and may be converted into carbonate
of lead on being passed through the converting chamber in the same manner
as before described for pure metallic lead; in fact, the dross is already a low
oxide well adapted to treatment in the converting chamber as before described
for the first stage of the process by this method.
The second part of the Invention relates to the finishing and improvement
of the ordinary white leads of commerce, and which contain portions of the
oxide and acetate of lead and sometimes particles of metallic leal, and this
Invention consists in subjecting a mass of the said white lea mixed with
water and heated to the action of a volume of carbonic acid gas in the manner
fully described hereafter, whereby the said mass is converted into pure carbonate
of lead. The ordinary white lead of commerce is produced by the action upon
metallic lead of heat, moisture, the vapor of vinegar, and carbonic acid gas.
In this process, however, the conditions are seldom so favorable that the
entire mass of metallic lead is converted into a pure carbonate of lead, the
resulting material, although mainly a carbonate, containing oxide and acetate
of lead. In order to reduce the material thus obtained to a pure carbonate of
lead I make use of the apparatus described in the fourth part of the Invention.
I introduce the material into a vessel L, Figures S and 9, and add water until
the mass is in a pasty condition. A stirrer M revolves in the vessel and
carries a number of arms or blades, the action of which maintains the mass at
a uniform consistency. The material in the vessel is then washed with water
several times in order to remove the superfluous portion of acetate of lead
which may be mixed with the mass, and the latter is then heated to and
maintained at a temperature of from 100 to 130 degrees Fahrenheit by means
of a jet of steam introduced through a pipe P which extends nearly to the
bottom of the vessel. When the entire mixture is at the proper temperature
carbonic acid gas is forced through a pipe P₁ into the mass of the material
uatil the latter is converted into a pure carbonate of lead. During this
process the mass is frequently examined and may be treated with a solution of
chlorine when desired to decompose impurities and improve the color of the

page_text: material. The lead products obtained in the manner described in the first
and third parts of the Invention may be also treated and finished substantially
as set forth in the second part of the Invention, after which the products are
transferred to the ordinary drying tables, dried, and put up for market. By
this process the condition of the lead when dried is such that it does not require
grinding to produce uniformity and fineness in quality, as it is already an
impalpable powder.
The third part of the Invention relates to the manufacture of white lead or
carbonate of lead from lead ores or minerals containing carbonate of lead
without reducing the said ores or minerals by fire; to accomplish this purpose
the native carbonates or lead ores are crushed and washed thoroughly with
chlor-acetic acid largely diluted with water and then ground in water into an
impalpable powder, during which operation the greater bulk of the impurities
are washed away and the carbonates settle in the vessel, the water is to be
heated from 100 to 140 degrees Fahrenheit. The whole mass thus prepared
is now treated in the apparatus described in the third part of this Invention
with chlor-acetic acid for the purpose of discharging the coloring matter and
decomposing all accidental impurities. The chlorine and acetic acid form
oxalic acid thus subjecting the mass to the best reducing and bleaching agents.
After this carbonic acid gas is applied to the mass under a pressure and a
stream of carbonic acid gas is passed through the mass until all its particles
are converted into a true carbonate; should copper or cobalt be present
they are to be extracted by the application of ammonia water in the place
of chlorine.
The fourth part of the Invention relates to an apparatus for finishing and
purifying the lead products by washing and treating them with acids and gases.
For this purpose I prepare a suitable vessel L, Figures 8 and 9 in which
is a rotary stirrer M arranged. When gases or other substances are to be
applied under a pressure the mouth of the vessel is to closed by a cover M
which is divided; the parts being drawn together by screw bolts N, the edges
of the parts are provided with claws O which catch over the upper lip of the
vessel as shown. The shaft of the stirrer is girdled by a stuffing box Q;
R, R, are apertures with valves for the admission and withdrawal of the
contents. Pipes P, P¹, pass through the cover and enter the body of the
vessel; these pipes are intended for the admission of steam, acid solutions,
gas, or whatever substances or chemicals it is desired to introduce. The lead
products obtained as described in the first, second, and third parts of the
Invention are placed in the vessel L, warmed, stirred, and treated with solutions
and gases as herein-before described. The solutions and gases may be intro-

page_text: duced through one of the pipes P' which are intended to communicate
with a force pump or other suitable medium for supporting the required
degree of pressure.
In the fifth part of the Invention the metallic lead is prepared or formed
properly for piling up on the shelves, with wide spaces or interstices between
them, by means of an iron wheel C, Figure 1, which receives the molten metal
from a melting pot D, and throws it by its paddles, on which the metal drops,
with great force against a flat iron shield E set up in front of the wheel.
The wheel is revolved with great velocity and throws the melted lead against
the iron shield to flatten it in irregular shapes or spangles which present
a great amount of corroding surface and lie loosely together when piled.
Having described the nature of this Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is,-
First, theimproved method of converting metallic lead into a true carbonate
of lead by the direct action of air, water, heat, acetic acid, chlorine, and carbonic
acid, substantially in the manner herein described.
Secondly, subjecting the metallic lead to a moistening mist with a fine
spray of water or slightly acidulated water, substantially as herein described.
Thirdly, subjecting the corroded lead to a similar moistening with dilute
acetic acid, substantially as herein described.
Fourthly, subjecting the lead product to the action of carbonic acid gas
under a pressure, substantially as herein described.
Fifthly, the employment of chlorine during the process of conversion of the
metallic lead into a carbonate, substantially as and for the purpose specified.
Sixthly, the application of carbonic acid either in the form of a gas or
a solution during the process of finishing, substantially as and for the purpose
set forth.
Seventhly, the application of chlorine during the finishing process, sub-
stantially as herein shown and described.
Eighthly, the method of obtaining white lead from lead ores or minerals,
substantially as herein described.
Ninthly, treating lead ores as minerals with carbonic acid and chlorine,
substantially as described.
Tenthly, treating the ordinary white leads of commerce with carbonic acid
and chlorine, substantially as described.
Eleventhly, the method of obtaining white lead from lead oros, substantially
as herein described.

page_text: Twelfthly, I claim as improved articles of manufacture the carbonates of
lead produced, substantially as herein described.
Thirteenthly, the construction of the converting chambers, substantially as
herein described.
Fourteenthly, the employment of the elevator in connection with the
converting chamber, substantially as herein described.
Fifteenthly, an apparatus for finishing lead products made substantially as
described.
Sixteenthly, the apparatus for converting metallic lead into scales operating
substantially as described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto
set my hand and seal, this Ninth day of December, in the year of
our Lord One thousand eight hundred and sixty-seven.
A. M. CLARK. (L.S.)