IMPROVEMENTS MiLaman An WurmD LEAD AND ADDADATIS THEREFOR"
Year: 1873

page_text: LETTERS PATENT to William Thompson, of No. 101, Wandsworth
Road, in the County of Surrey, for the Invention of "IMPROVEMENTS
MiLaman An WurmD LEAD AND ADDADATIS THEREFOR"
PROVISIONAL SPECIFICATION left by the said William Thompson
at the Office of the Commissioners of Patents, with his Petition, on
the 28th April 1873.
I, WILLIAM THOMPSON, of No. 101, Wandsworth Road, in the County
3 of Surrey, do hereby declare the nature of the said Invention for "Im-
PROVEMENTS IN THE MANUFACTURE OF WHITE LEAD AND APPARATUS THEREFOR,"
to be as follows:-
In preparing white lead it is of great importance that the blue lead
acted 'on should be as pure as possible, and free from dross or other
matter which can float on the surface of the molten metal; also that
the fluid lead should be drawn off at a regulated temperature.
-
One part of this Invention relates to the construction and use of
melting apparatus, whereby the purity of the metal to be operated on

page_text: .
can be secured and its temperature can be regulated. For this purpose
I construct a melting pan with three compartments separated from each
other by vertical partitions. One of these compartments is used for
melting the lead. From another of the compartments which com-
municates by an opening at its bottom with the melting chamber, the
fluid lead is taken, and being thus supplied from the bottom of the
melting chamber, it is free from dross or scum. The third compartment
is kept cooler than the melting chamber, being arranged so as to be
farther from the furnace heat, and being supplied as required with the
lead to be melted. It communicates with the melting chamber by a.]
passage governed by a sluice or valve. Whenever the lead in the
melting chamber becomes over heated a portion of the cooler fluid could
be run into it from the third chamber, and thus the temperature may be
regulated before any lead is withdrawn.
Instead of one compartment as last described there may be two or more 1
containing metal at different temperatures, and serving as reserve
chambers for the supply of the melting chamber.
Lead is more readily acted on when a large surface of it is exposed
and when it is of a comparatively loose texture.
Another part of my invention relates to its preparation in such a
condition. For this purpose I provide a cylinder open at the ends and
having a lip projecting inwards at each end. I mount this cylinder on
rollers and cause it to revolve thereon, and I pour the fluid lead into it.
By the rotation of the cylinder the lead is spread in a thin sheet of open
texture over its interior periphery, which sheet can be cut longitudinally
and removed and flattened. To facilitate its removal the lip at one end
of the cylinder may be made moveable.
In order the more quickly to cool the lead during this operation I
make the cylinder with a casing supplied with cold water, or I cause the
cylinder to revolve with the lower part of its periphery immersed in a
trough of water, or I pour water over its exterior periphery, and in order
to keep it moistened I prefer to coat it with felt or other fibrous or
spongy material.
In order to granulate the lead I mount a roller in bearings and cause
it to revolve with a sloping knife adjusted near to its circumference;
pour the melted lead into the angular space above the knife whence it
issues in a thin stream through the passage between the edge of the
I

page_text: Anne and the cynnder, and drops into water below, wherein it sets in
granules.
The cylinder above described by which the lead is made into sheets,
may be also used as the roller for granulation.
In the manufacture of white lead the blue lead in sheets or granules or
other forms is acted on by acids and vapours in closed chambers
maintained at suitable temperatures. In charging and discharging
these chambers much time is usually lost and there is a considerable
waste of the gases and vapours employed as re-agents, and also a waste of
heat because the chambers must to a great extent be cleared and cooled
before workmen can enter them.
Another part of my Invention relates to means for avoiding such loss
and waste. For this purpose I construct chambers with doors at each
end and lines of rails through them, and I provide trucks to run on
these rails. Outside the chamber I load a truck with the blue lead
preferably arranging it in alternate layers of the thin sheets, and the
granules supported upon open trays or gratings. I then open one of
the doors of the chamber and run in the truck. When the lead has
been sufficiently acted on I open the opposite door of the chamber and
withdraw the truck. For continuous working both doors may be opened
at the same time and a truck charged with blue lead may be pushed in
so as to push out the truck of lead that has been operated on, and to
take its place in the chamber.
It is to be understood that the chambers and trucks are formed
wholly or principally of material such as slate, earthenware, glass, or
the like substances that are not acted on by the re-agents used for acting
on the lead; also that the gases and vapours are supplied to the
chamber preferably at their lower parts, and that to ensure a circulation
through the chambers fans or other mechanical propellers may be
employed, made of materials not acted on by the re-agents.
In charging the trucks with the blue lead to be operated on it is
preferable to brush over the surface of the lead with acetic acid for the
purpose of removing oxide that may have been formed thereon, and
leaving the clean metallic surface to be acted on in the converting
chamber.
The gases and vapours supplied to the converting chambers are
preferably heated before their admission thereto and are admitted to the
;

page_text: lower part of the chamber, their heat causing them to rise and diffuse
themselves therein. The most important gas employed is carbonic acid
as is well-known, and with this is usually mingled acetic acid or other
acid vapours, which may be conveniently produced in steam jacketted
pans or vessels, the distilled water from the steam condensed therein
being employed to dilute the acids.
The carbonic acid is best introduced into the converting chambers at
such a temperature that it will rise and diffuse itself through the
chamber. For this purpose the carbonic acid may be sent through pipes
or vessels steam jacketted, and being thus warmed is mingled with the
acid vapours as they are introduced. By this method is avoided the
necessity for introducing steam into the chambers which has the effect
of diluting the reagents employed, and the temperature of the chambers
being maintained the reaction is accelerated.
SPECIFICATION in pursuance of the conditions of the Letters Patent, 1
filed by the said William Thompson in the Great Seal Patent Office
on the 28th October 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
THOMPSON, of No. 101, Wandsworth Road, in the County of Surrey,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-eighth day of April, in the year
of our Lord One thousand eight hundred and seventy-three, in the
thirty-sixth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said William Thompson, Her
special licence that I, the said William Thompson, my executors,
administrators, and assigns, or such others as I, the said William
Thompson, 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 OF WHITE LEAD AND APPARATUS
THEREFOR," upon the condition (amongst others) that I, the said William
Thompson, my executors or administrators, by an instrument in writing

page_text: 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 William Thompson, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement:-
In preparing white lead it is of great importance that the blue lead
acted on should be as pure as possible and free from dross or other
matter which can float on the surface of the molten metal, also, that
the fluid lead should be drawn off at a regulated temperature.
One part of this Invention relates to the construction and use of
melting apparatus whereby the purity of the metal to be operated on
can be secured, and its temperature can be regulated. For this purpose
I construct a melting pan with three compartments separated from
each other by vertical partitions. One of these compartments is used
for melting the lead; from another of the compartments, which com-
municates by an opening at its bottom with the melting chamber,
the fluid lead is taken, and being thus supplied from the bottom of
the melting chamber it is free from dross or scum. The third com-
partment is kept cooler than the melting chamber, being arranged so
as to be further from the furnace heat, and being supplied as required
with the lead to be melted; it communicates with the melting chamber
by a passage governed by a sluice or valve. Whenever the lead in
the melting chamber becomes overheated a portion of the cooler fluid
could be run into it from the third chamber, and thus the temperature
may be regulated before any lead is withdrawn.
Instead of one compartment as last described there may be two or
more containing metal at different temperatures, and serving as reserve
chambers for the supply of the melting chamber.
Lead is more readily acted on when a large surface of it is exposed,
and when it is of a comparatively loose texture.
Another part of my Invention relates to its preparation into such a
condition. For this purpose I provide a cylinder open at the ends,

page_text: and having a lip projecting inwards at each end. I mount this cylinder
on rollers and cause it to revolve thereon, and I pour the fluid lead
into it. By the rotation of the cylinder the lead is spread in a thin
sheet of open texture over its interior periphery, which sheet can be
cut longitudinally and removed and flattened. To facilitate its removal
the lip at one end of the cylinder may be made moveable.
1
In order the more quickly to cool the lead during this operation I
make the cylinder with a casing supplied with cold water, or I cause
the cylinder to revolve with the lower part of its periphery immersed
in a trough of water, or I pour water over its exterior periphery, and
in order to keep it moistened I prefer to coat it with felt or other fibrous
or spongy material.
In order to granulate the lead I mount a roller in bearings and
cause it to revolve with a sloping knife adjusted near to its circum-
ference. I pour the melted lead into the angular space above the knife,
whence it issues in a thin stream through the passage between the edge
of the knife and the cylinder, and drops it into water below wherein it
sets in granules.
The cylinder above described by which the lead is made into sheets
may be also used as the roller for granulation.
In the manufacture of white lead the blue lead in sheets or granules.
or other forms is acted on by acids and vapours in closed chambers
maintained at suitable temperatures. In charging and discharging
these chambers much time is usually lost, and there is a considerable
waste of the gases and vapours employed as re-agents, and also a waste
of heat because the chambers must to a great extent be cleared and
cooled before workmen can enter them.
Another part of my Invention relates to means for avoiding such
loss and waste. For this purpose I construct chambers with doors
at each end and lines of rails through them, and I provide trucks to
run on these rails. Outside the chamber I load a truck with the
blue lead, preferably arranging it in alternate layers of the thin sheets,
and the granules supported upon open trays or gratings, I then open
one of the doors of the chamber and run in the truck. When the
lead has been sufficiently acted upon I open the opposite door of the
chamber and withdraw the truck. For continuous working both doors:
may be open at the same time, and a truck charged with bluc lead

page_text: may be pushed in so as to push out the truck of lead that has been
operated on, and to take its place in this chamber.
It is to be understood that the chambers and trucks are formed
wholly or principally of materials such as slate, earthenware, glass,
or the like substances that are not acted on by the re-agents used for
acting on the lead, also that the gases and vapours are supplied to the
chambers preferably at their lower parts, and that to ensure a cir-
culation through the chambers fans or other mechanical propellers may
be employed made of materials not acted on by the re-agents.
In charging the trucks with the blue lead to be operated on it is
preferable to brush over the surface of the lead with acetic acid for
the purpose of removing oxide that may have been formed thereon,
and leaving the clean metallic surface to be acted on in the converting
chamber.
The gases and vapours supplied to the converting chambers are
preferably heated before their admission thereto, and are admitted to
the lower part of the chamber, their heat causing them to rise and
diffuse themselves therein. The most important gas employed is carbonic
acid gas, as is well known, and with this is usually mingled acetic
acid or other acid vapours, which may be conveniently produced in
steam jacketted pans or vessels, the distilled water from the steam con-
densed therein being employed to dilute the acids.
Instead of using steam jacketted pans I may in some cases use hot
water or hot air jacketted pans.
The carbonic acid gas is best introduced into the converting chamber
at such a temperature that it will rise and diffuse itself through the
chamber. For this purpose the carbonic acid gas may be sent through
pipes or vessels steam jacketted or hot air or hot water jacketted, and
being thus warmed is mingled with the acid vapours. as they are intro-
duced. By this method is avoided the necessity for introducing steam
into the chambers, which has the effect of diluting the re-agents
employed, and the temperature of the chambers being maintained the
reaction is accelerated.
I can also use corroding rooms with one door by using turntables with
lines of rails. in front. This will also render it unnecessary for those

page_text: -
they must do in all other methods of manufacturing white lead. I thus
prevent those employed suffering from the unhealthy and deadly fumes
to which they are at present exposed.
I use a generator for making my carbonic acid gas, and, in order to
have a continuous supply of this gas to the corroding chambers or rooms
I have one or more gasometers.
In order to make the foregoing description clear I hereto append a
Sheet of Drawings having figures and letters of reference marked
thereupon.
In these Figure 1 is a vertical section, and Figure 2 a plan of a
melting pan constructed according to my Invention. It is divided into
three or more compartments, the middle one A being exposed to the
direct action of the fire is appropriated to the melting of the metal. It
is separated from the other compartments B, C, by partitions, near the
bottom of which are holes that can be stopped by plugs, and one of
these compartments B is that from which the melted metal is taken by
the ladle. Being supplied through the plug hole E from the lower
part of the melting compartment A the metal is free from scum or
dross.
Fresh metal to be melted is supplied to the compartment C, and
admitted to the middle compartment A by the plug hole E¹. As the
metal in C is less exposed to the direct action of the fire, and can at will
be cooled down by the supply of colder metal from the compartment C
to the compartment A, it serves to temper the heat of the metal therein
to that heat most suitable for the purpose. It also prevents the great
loss by the old process inevitable from the blue lead oxidizing so freely
in consequence of its being overheated.
Figure 3 represents a longitudinal section, and Figure 4 an end view
of the cylinder used for producing the sheets of blue lead, as herein-
before described. It has at each end a lip F & F¹ projecting inwards,
and leaving a circular opening in the middle, through which melted
metal can be poured into the interior. One of the lips as F may be
fixed, and the other F may be made moveable, so that it can be taken
off to facilitate the removal of the cylindrical sheet from the interior of
the cylinder. To secure tightness of its joints to the cylinder it is made

page_text: slightly conical at F, fitting into a corresponding conical recess in the
cylinder, to which it can be fixed by screws.
The cylinder may be made with a water jacket G which can be
charged with water from time to time for the purpose of cooling the
cylinder; or instead of such a jacket the exterior of the cylinder may be
lined with felt or other fibrous or spongy material which can be kept
moist with water. Each end the cylinder has a flange which rests on
grooved rollers or pulleys K, K. The cylinder is caused to revolve, and
the melted metal poured into its interior is spread by the centrifugal
force into a thin layer over its inner surface or circumference, wherein it
sets as a thin sheet of loose texture. This sheet can be ripped longi-
tudinally by a knife and removed, and if necessary the lip F" at the one
end can be taken off in order that the sheet may be taken out more
readily.
Figure 5 represents a longitudinal section, and Figure 6 a cross section
of the apparatus for granulating the lead. It consists of a roller L made
to revolve in the direction of the arrow. Against this roller is placed an
inclined knife or scraper M, which can be adjusted so as to leave a
narrow slit between its edge and the surface of the roller. Melted lead
poured into a wedged-shape space above. the scraper M flows through the
narrow slit in a thin broad stream, and drops into water in a trough N,
wherein it sets in the form of granules.
Figure 7 represents a longitudinal section, and Figure 8 a part plan
of a chamber arranged according to my Invention for the conversion of
lead. In the chamber and also in Figure 9 is shown the trucks. The
chamber O has a door at each end, and although a single door is shown
in the Drawing in order the better to ensure tightness and to prevent
cooling I prefer to use two or double doors at each end. Rails P are
laid along the floor of the chamber, and extend a convenient length
beyond it either way. The trucks which run on these rails are made
with numerous shelves or trays on which are placed the slicets and
granules of lead to be converted into white lead. While one truck is
within the chamber having its contents subjected to the action of the
gases and vapours supplied thereto in any known manner, another of the
trucks in the position as shown outside of the chamber may be receiving
a charge of metal to be operated on, or may be cleared of the converted
lead in the manner herein-before described.

page_text: Figure 10 represents my arrangement as herein-before described for
the purpose of rendering the carbonic acid gas of such a temperature as
to be more suitable for quickly rising and diffusing itself through the
converting chamber (Figures 7 and 8). It will be seen by reference to
this plan view (Figure 10) that the gas generated passes, after coming
through the gasometers into the pipe R, which pipe is surrounded by.a
steam jacket S, to which steam is admitted from a boiler.
Instead of steam hot water or hot air jackets may be used.
i
T is a pan for the acid, and contains at its bottom a coil of pipe
through which steam or hot water is led. The fumes from the acid pass
from the pan and unite with the carbonic acid gas at the junction U.
The waste steam escapes at V. By this method I can at all times know
the strength of the re-agents, as no steam is mixed with them either
before or after being passed into the chambers. This cannot possibly
be done where large jets of steam are introduced without any knowledge 1
of their heat or the quantity passed into the corroding rooms.
Having thus described. the nature of my Invention, and in what
manner the same is to be performed, I would have it understood that I
do not claim generally the conversion of metallic lead into white lead by
exposing it to the action of gases or vapours in closed chambers, but I 2
claim,
Firstly. The use for melting the lead to be converted of a vessel
divided into several compartments, in the manner and for the purposes
substantially as herein set forth.
Secondly. The method substantially as herein described in reference to 2
Figures 3 and 4 of producing thin sheets of lead of open texture for the
purpose of then being converted into white lead.
Thirdly. The method substantially as described with reference to
Figures 5 and 6 of producing granulated lead for the purpose of its being
converted into white lead.
Fourthly. The arrangement of chambers with their rails and trucks
substantially as described for the purpose of enabling workmen to charge
or discharge the material without being exposed to the injurious and
deadly fumes of the converting chambers.
I claim also the method and arrangement for continuously supplying a
and raising the temperature of the carbonic acid gas in order to make it

page_text: more quickly rise and diffuse itself in the converting chamber without
any admixture of steam, also as described.
In witness whereof, I, the said William Thompson, have hereunto
set my hand and seal, this Twenty-second day of October, in
the year of our Lord One thousand eight hundred and seventy-
three.