IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD
Year: 1877

page_text: LETTERS PATENT to William Thompson, of 120, Stainsbury Road, Limehouse,
East, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF WHITE
LEAD"
PROVISIONAL SPECIFICATION left by the said William Thompson at the
Office of the Commissioners of Patents on the 7th November 1877.
WILLIAM THOMPSON, of 120, Stainsbury Road, Limehouse, East.
MENTS IN THE MANUFACTURE OF WHITE LEAD."
"IMPROVE-
My Invention consists in improvements upon my former Patent, dated 28th April
1873, No. 1532, for improvements in the manufacture of white lead.
I line the bottom or any other part of the converting chamber with sheet lead,
cement, slate, glazed bricks, or any other substance that will resist water, acids, and
carbonic acid gas. The lining is brought high enough to prevent the liquors from
coming over the door sill.
I also stop off two-thirds, or more, of the centre part of the bottom of chambers,
then the water and acids are all or part of the way round the chambers, and not all
over the bottom surface.
I can also use separate vessels for acids and water inside chambers made of any
suitable materials; and where pots are required for the acid and water I use leaden
pots, and not earthenware as at present, thus I save the expense of the earthenware
pots and the space taken up by them, inasmuch as the leaden pots are converted
into white lead by the same vapours, gases, and air as the lead placed in the
chambers. These pots are made by a revolving cylinder made of cast iron or steel,
bored out to the shape of the pot or pots required. This is made in two halves for
the purpose of getting the pots out; or it may be made with the ends to take out,
or any other way thought best.
When the cylinder is completed I pour the melted lead into a hole for that
Pavics 8d71

page_text: •
purpose; the cylinder then revolves on wheels, or rollers, or centres, and can be
worked by steam or hand. Thus the leader pots are made.
In the centres of the water and acids before mentioned, in the bottom of the con-
verting chambers, I fix a copper pipe, tinned or earthenware pipe, or any other
suitable substance, through which is passed hot water, hot air, or steam; thus the
necessary heat and vapours are raised. The heating surface of the pipes is governed
by the size of the chambers.
And in order that I may at all times know the exact heat of chambers I use
a thermometer, made to indicate outside; I also use a thermometer inside, but this
cannot be clearly seen in consequence of the rising vapours. I find the difference
of the thermometer being outside and inside is about five degrees; this I allow for ;
therefore I can at any time see the exact heat of chambers.
I use condensed or rain water, filtered or condensed steam, to dilute the acids.
The amount of water is governed by the strength of the acids.
I. use an earthenware pan or slate cistern for mixing the acids and water. It
passes from the pan into a worm or worms, made of earthenware, or copper, or any
other suitable substance. These worms answer two important purposes, being made
mathematically correct to supply, the water consumed by, vapours in the converting
chambers; they also mix the acids and water thoroughly before entering the
chambers.
Should the water at any time rise in the converting chambers above the required
height it is at once syphoned off by an internal arrangement for that purpose. I
also use a float outside, by which I can see the height of the water during the day;
at night I leave the cock open, connected to the syphon.
I fix two or more fans inside the converting chambers; arrangements are made
to work them outside. These fans are used for mixing the acid vapours and atmo-
spheric air with the carbonic acid gas. When the chambers are charged. these fans
are worked at intervals. I work both fans at the same time, one turning to the
right the other to the left hand; these can be worked by hand or steam. These
fans are made of any material suitable for the purpose.
At the top of the converting chambers, inside, I fix a glass roof, leaving a space
between the outer roof; also a space in the centre and at each side to allow the
accumulated vapours to run down the sides of chambers into the water at the
bottom, thus preventing all possibility of the vapours or gasses escaping, and by
their continually running into the water they become comparatively harmless. This
internal glass roof also prevents the continuous dripping upon the blue lead during
the process of its being converted into white lead.
If a single roof only, the vapours would cause a continuous dropping like rain;
this would injure the process very much. I fix a small chamber, standing upon the
outer roof; this may be made of any shape, or length, or any materials best suited
for its purpose. It is connected to the converting chambers by a number of small
holes at the lowest point; these holes will come immediately over the glass roof
before mentioned. From this upper chamber I can more readily form a vacuum.
than from the body of the chambers. When a vacuum is formed the gases enter
more readily and effectually. Above this chamber is fixed one or more glass globes
with two connections, one to the chamber, the other to the discharge pipe that leads.
into a receiver, made for the purpose of receiving all spent gases and vapours.
Before passing up the chimney steam is blowing into this receiver, and sometimes
air is passed into it; then all escapes together into a pipe in which superheated
steam is blown and leads into the chimney, thus all passed away without having the
least effect on the work people. This receiver is made of any suitable materials for
its purpose.
In order to keep up the required heat in the converting chambers from Saturday
till Monday, and at nights, I fix one or more small boilers, made of copper or any
other suitable materials. These boilers are heated by gas, and supplied with water
from a self-acting cistern, through which a pipe is fixed, and gas, steam, or hot air,
or hot water is passed through this pipe to heat the water in cistern. The water

page_text: from the boilers enter the copper pipe before mentioned in the centre of water in
the converting chambers.
I convey the gases and air into the centre of the chamber by small pipes, made
of glass, earthenware, or copper, tinned. These pipes are made to disconnect at
pleasure.
I fix about the centre of each converting chamber small double doors; the inner
one is made of glass, the outer of any suitable materials. Both doors are made
perfectly tight, therefore by opening the outer door I can at all times see how the
process is going on without the slightest escape of gas or vapour.
I can also use double doors for the converting chambers, the inner of glass, the
outer of any substances best suited for the purpose. I make these doors to work
on hinges. These doors are perfectly secured by arrangements made for that
purpose.
Near to the bottom of the converting chambers I fix two small vessels, connected
together by a pipe, each having a stop-cock; a pipe leads from these into the .
bottom of the chambers. These vessels are made for supplying any deficiency of
acids that may be required during the process. These vessels are so arranged that
it is not possible that any vapours can escape from them..
I use for producing the carbonic acid gas American or English marble dust, chalk,
whiting, or charcoal, on to which I pour hydrochloric or oil of vitriol. I can
also make the carbonic acid gas from coke, by fixing an oven for that purpose.
I fix one or more purifiers, through which the carbonic acid gas passes before going
into the gasometers. I also have an intermediate pipe, by which I can pass the gas
direct from the purifiers into the converting chambers. This intermediate pipe also
answers as a relief valve to keep the gas from blowing back into the acid boxes,
which is so frequently the case by the old method. Improvements in the shapes
of the blue lead for its conversion into white, by which the gases and vapours pass
internally as well as externally, thus insuring a better result than the old system
can possibly give.. This is done by forming a mould especially for that purpose.
I use a copper pan or plate for granulating the blue lead. These will be washed
with French or English chalk, or whiting, mixed with water. These may be made
any shape best suited for the purpose.
I sometimes use moulds made of wood for converting the blue lead into the
various shapes for its conversion into white lead. I find the lead made by this
method is much softer than when cast in iron moulds.
I can also use the blue lead without being melted the second time by cutting into
sheets by a machine for that purpose. By this method I save the waste that is lost
by melting the blue lead.
I can also use a V slide for passing the carriages in and out of the converting
chambers with the blue and white lead. These slides may be made of steel, brass,
slate, or wood, or any other suitable materials.
I can also use a steam chest for heating the converting chambers, having a small
cistern on the top for water and acids. This may be made of lead, slate, or earthen-
ware, or wood lined with sheet lead.
I can make the converting chambers of common bricks or glazed bricks set in
cement, and lined with cement or glazed tiles.
I can also make the chambers of slate or wood lined with lead or copper, tinned, or
any other materials best suited for the purpose.
I can also use steam at any time when required to regulate the heat of chambers.
I can also use ammonia. at intervals of any strength or quantity best suited for
the process.
I can use lead, tin, or gutta percha, or india-rubber, copper, glass, or earthen-
ware pipes for passing the gases and air into the chambers, or any other known
substance.
I can use a meter for measuring the gas and air before going into the chambers...
I can also use separate vessels for the gases and air. These are fixed in the most
convenient place for passing the gases and air into the chambers.
.

page_text: I fix one or more condensers. These condensers are for receiving the carbonic
acid gas from the gasometers when necessary. I pass amospheric air into the
condenser.
I can also pass the gas direct from the gasometers into the converting chambers.
On these condensers are fixed a pressure guage. The above are made of copper,
lead, earthenware, slate, or wood lined with sheet lead.
From the condensers before mentioned the gas and air passes into a receiver
_before entering the converting chambers. On these receivers are fixed a thermo-
meter and a pressure guage.
This is kept about two or three degrees hotter than
the converting chambers. Heated gases and air enter more freely than when cold,
it is very difficult to pass cold gases and air into hot gases and hot air.
I use three or more pumps,-
No. 1 is used for pumping the gases from the gasometers into the condensers,
and from them into the receiver, before mentioned.
No. 2 is used for pumping the gases, and vapours, and air from the converting
chambers; back into the gasometers. By this pump I can pass the gases backward
and forward at pleasure, as best suited to the process.
No. 3 pump is used for forming a vacuum in the receiver that stands on the top
of the converting chambers. On the pipe connected to this pump is fixed a vacuum
guage.
This pump is also used for pumping air or water into the converting chambers.
It may also be use for "pumpg the gases, vapor, and air backward and forward
from the chamber without going into the gasometers.
Improvement in the Melting Pan.-Opposite the two internal lips I fix jackets
reaching from top to the bottom of pan. These jackets are filled with a non-
conductor of heat, thus preventing the flues from overheating the part where the
melted lead enters from the body of pan into the inner deep lip, from which the
metal is ladled. I use a cover for the melting pan. In the back of cover is fixed
a small chimney leading into the shaft. The cover keeps the lead from oxydizing;
it also keeps the heat from those employed, and the chimney carries away all
fumes.
At the end of the process I commence cooling down the converting chambers, and
passing away all gases and vapours as follows:-No. 1 pump is put to work,
pumping in cold air; I then let out the hot water from the bottom of the chambers;
as the hot water is passing out, cold water is going into the chambers; this water
passes at once into a slate cistern buried in the ground; this cistern has about
four inches of cold water in the bottom, and a pipe in the water; the hot water dives
into the cold water, thus putting a stop to all possibility of vapours escaping; this
cistern has double doors made tight, therefore not the slightest chance of the least
escape. I then put No. 2 pump to work, pumping the cold air from the chamber that
No. 1 is pumping in, thus all spent gases and vapours are passed into a gasometer;
this is connected with a receiver, into which all spent gases and vapours are passed.
No. 3 pump is put to work for a final clearance, also to pump water into and
thoroughly cleanse the receiver for all spent gases.
The gasometers before mentioned are made to rise and fall by means of a gutta
percha pipe. When the gasometer is full it is passed into the receiver for spent
gases; into this is blown steam; from this all passes together into a pipe connected
with the chimney; into this pipe is blown superheated steam; thus all the deadly
gases and vapours are passed away harmless up the chimney without having the
slightest effect on those employed, and the chambers clear of all gases and vapours,
and as cold as when the process commenced.
I also have two air channels leading into the chimney from the outside of the
building; this increases the draught very much; thus every possible means are used
to prevent this deadly scourge that is so common in the old method of manufacturing
white lead.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
"
said William Thompson in the Great Seal Patent Office on the 29th April 1878.
WILLIAM THOMPSON, of 120, Stainsbury Road, Limehouse, East. IMPROVE-
MENTS IN THE MANUFACTURE OF WHITE LEAD."
In the manufacture of white lead it is very essential that the blue lead acted on
should be as pure as possible and free from dross or scum or other matter which
will float on the surface of the molten metal, and 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 a melting pan,
whereby the purity of the metal to be operated upon can be secured, and its
temperature regulated. For this purpose I construct a melting pan with three
compartments, A, B, C, separated from each other by vertical partitions, as shewn
in Figures 1 and 2, Figure 1 being a plan of the said melting pan, and Figure 2 a
vertical section of the same. The compartment A is used for melting the lead;
from the compartment B, which communicates by an opening at its bottom with
the melting chamber, the fluid lead is taken. The lead thus supplied from the
bottom of the melting chamber is free from the dross or scum. The third compartment
C is kept cooler than the compartment A, being so arranged as to be farther from
the furnace heat, and being supplied as required with the lead to be melted; it.
communicates with the compartment A by an opening governed by a plug. When-.
ever the lead in the compartment A becomes overheated a portion of the cooler
fluid is let into it from the compartment C, and thus the temperature may be
regulated before any lead is withdrawn. Opposite the two internal compartments
B, C, on the outside of the plan I form jackets D, E, reaching from the top to the
bottom of the said pan; these jackets are filled with a non-conductor of heat, such
as charcoal and whiting, thus preventing the flues from overheating the part where
the melted lead enters from the body A of the pan into the inner deep compart-
ment B from which the metal is ladled, and preventing overheating also of the
compartment C, containing the lead to be melted. I place a cover over the said
melting pan, in which cover is fixed a small pipe leading into the chimney to:
carry away all fumes; this cover keeps the lead from oxydising, and also protects
those employed from heat.
"Figure 3 represents a longitudinal section of my apparatus for granulating the
lead; it consists of a roller F against which is placed an inclined knife or scraper F',
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 Fflows through the narrow slit in a thin broad stream, and drops upon
a cone-shaped piece G of copper or other suitable material. The lower part of this
cone-shaped piece forms a receptacle G' for the lead, which assumes a granulated
formation. The part G I prefer to wash with English or French chalk, or with
whiting mixed with water.
In order that the gases aud vapours may pass internally as well as externally
over the blue lead during its conversion into white lead, thus insuring a better
result than the old system, I use a mould in which to cast such lead in such a shape
as to admit of the said passage of vapours. I prefer to form these moulds of wood,
as the lead cast in such moulds is softer than that cast in iron moulds. I may,
however, if desired, use moulds inade of iron or other suitable material.
I sometimes use the blue lead without being melted the second time by cutting
it into sheets by a machine for that purpose. In this case I save the waste that.
is lost by melting the blue lead.
One of the moulds constructed according to my Invention is shewn in Figures
4; 5, and 6, Figure 4 being a plan of the lower part of the said mould; Figure 5,
an inverted plan of the upper part; and Figure 6, a longitudinal section of these.
moulds placed together.

page_text: Figure 7 shews a longitudinal section of two pieces of lead, each of which is cast
in the said moulds, and shews the same placed one on the other. It will be seen
that when these castings are so placed there is a passage H between each rib or bar
of the casting and a passage H' through such pieces, so that the gas vapours can
act upon outer and inner surfaces of the same.
Although I have here illustrated one of the said moulds as being the one I prefer
to use, I may use moulds which will produce any other form of casting desirable.
Another part of my Invention relates to the chamber for converting the blue
lead into white lead, and is shewn in Figures 8 and 9, Figure 8 being a plan, and
Figure 9 a transverse section of the said converting chamber; this chamber I has a
double door at each end, the inner one being formed of glass to permit inspection
during the conversion of the lead. Rails J are laid along the floor of the chamber,
and extend beyond it in either direction. The trucks K, which run on these rails, are
provided with numerous shelves or trays, on which are placed the sheets or 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 acids and vapours, the other truck
is in a position outside of the chamber to receive a charge of metal to be operated
upon, or to be cleared of the converted lead.
I line the bottom or any other part of this converting chamber with sheet lead,
cement, slate, glazed bricks, or any other substance that will resist water, acids,
and carbonic acid gas, the said lining being brought high enough to prevent the
liquids from rising over the door sill.
I also stop off two-thirds or more of the centre part of the bottom of the
chamber, so that the water and acids are all or part of the way round the chamber,
and not all over the bottom surface, in which case too much vapour would be
generated.
I may in some cases use separate vessels for acids and water inside this chamber,
made of any suitable material; and where pots are required for the acid and water
I use leaden pots, and not earthenware as at present in use, thus saving the
expense of such earthenware pots and the space taken up by them, inasmuch as
the leaden pots are converted into white lead by the same vapours, gases, and air
as the lead placed in the chamber. These pots are made by a revolving cylinder
made of cast iron or steel bored out to the shape of the pot or pots required; this
cylinder is made into two halves for the purpose of removing the pots, or it may
be made with the ends to take out, or in any other suitable way.
When the cylinder is completed I pour the melted lead into a hole for that
purpose; the cylinder is then revolved on wheels, or rollers, or centres, either by steam
or hand, and thus forms the leaden pots. In some cases I may form these pots by
stamping out.
In the centre of the water and acids in the bottom of the converting chamber, I
fix a copper, tinned, or earthenware pipe, or a pipe of any other suitable substance,
through which is passed hot water, hot air, or steam, whereby the necessary heat
and vapours are raised, the heating surface of the pipe being governed by the size
of the chamber.
In order that I may at all times know the exact heat of the chamber, I use a
thermometer to indicate such heat outside, and I also use a thermometer placed
inside, but this cannot be clearly seen in consequence of the rising vapours. I find
the difference of the thermometer outside and inside is about five degrees, and this I
allow for, so that I can at any time see the exact heat of the chamber from the
outside.
Condensed or rain water, filtered or condensed steam, is used to dilute the acids,
the amount of water being governed by the strength of such acids.
The acids and water are mixed in an earthenware pan or slate cistern, and pass
from the same into a worm or worms L made of earthenware, copper, or any other
suitable substance, such as shewn in Figure 10. These worms answer two important
purposes, being made mathematically correct to supply the water consumed by the

page_text: vapours in the converting chamber, and also to mix the acids and water thoroughly
before entering such chamber.
Should the water at any time rise in the converting chamber above the required
height, it is at once syphoned off by an internal arrangement for that purpose. I
also use a float outside, by which I can see the height of the water during the day.
At night I leave the cock connected to the syphon tube open.
I fix two or more fans constructed of any suitable material, and one of which is
shewn at M, Figure 9, inside the converting chamber, these fans being worked from
the outside, and used for mixing the acid vapours and atmospheric air with the
carbonic acid gas. When the chamber is charged, both fans are worked at intervals
by hand or steam power, and at the same time, one turning to the right, and the
other to the left hand.
At the top of the converting chamber inside I fix a glass roof N, leaving a space
between the outer roof N¹, and also a space in the centre and at each side to cause
the accumulated or condensed vapours to run down the sides of the chamber into
the water at the bottom, thus preventing all possibility of the vapours or gases
escaping, and causing them continually to run into the water, and thus become
comparatively harmless. This internal glass roof also prevents the continuous
dripping of the condensed vapours upon the blue lead during the process of its
being converted into white lead. If a single roof only were used the vapours
would cause a continuous dripping like rain, which would materially injure such
process.
3
On the outer roof is a small chamber O which may be of any shape or length or
any material best suited for the purpose. It is connected to the converting chamber
by a number of small holes O' immediately over the glass roof before mentioned;
from this upper chamber I can more readily form a vacuum than from the body of
the converting chamber, as the gases enter readily and effectively into the same.
Above this chamber O is fixed one or more glass globes P with two connections,
one P¹ to the chamber N, the other P2 to the discharge pipe that leads into a
receiver Q, shewn in Figure 11, for the purpose of receiving all spent gases and
vapours before passing up the chimney; steam is forced into this receiver and some-
times air, when all escape together into a pipe, close to the end of which a jet of
superheated steam is arranged in the chimney, so that all vapours pass away without
having the least effect on the workpeople. This receiver is made of any material
suitable for the purpose.
In order to keep up the required heat in the converting chamber from Saturday
till Monday, and at nights I use one or more small boilers made of copper, or any
other suitable material, which boilers are heated by gas and supplied with water
from a self-acting cistern through which a pipe is fixed, and gas, steam, or hot air, or
hot water is passed through this pipe to heat the water in the said cistern. The
water from the boilers enters the copper pipe before mentioned in the centre of the
water in the converting chamber.
I convey the gases and air into the centre of the chamber by small pipes made
of glass, earthenware, or copper tinned; these pipes are made to disconnect at
pleasure.
I fix at about the centre of the converting chamber a small double door, the inner
part of which is made of glass, and the outer part of any suitable material; both
doors are made perfectly tight, so that by opening the outer door, I can at all
times see how the process is going on without the slightest escape of gas or vapour.
I also use double doors for the converting chamber as herein-before described, the
inner one being formed of glass, and the outer one of any substances best suited for
the purpose. I make these doors to work on hinges, the said doors being perfectly
secured by arrangements made for that purpose.
Near to the bottom of the converting chamber I fix two small vessels connected
together by a pipe, each vessel having a stop-cock. A pipe leads from these vessels
into the bottom of the chamber. These vessels are for the purpose of supplying any

page_text: deficiency of acids that may be required during the process, the stop-cocks of the
same being so arranged that it is impossible for any vapours to escape during the
introduction of such acid into the converting chamber, provided the aforesaid cocks
are. properly manipulated.
For producing the carbonic acid gas I prefer to use American or English marble
dust, chalk, whiteing, or charcoal, on to which I pour hydrochloric acid or oil of
vitriol; or I may make such carbonic acid gas from coke by fixing an oven for that
purpose.
I also use one or more purifiers, through which the carbonic acid gas passes before
going into the gasometers, and I also use an intermediate pipe, through which I can
pass the gas direct from the purifiers into the converting chamber; this intermediate
pipe also answers as a relief valve to keep the gas from blowing back into the acid
boxes, which is frequently the case with apparatus at present in use.
For moving the carriage K, containing the blue or white lead, in and out of the
converting chamber, I use a slide, which may be made of steel, brass, slate, or
wood, or any other suitable material, or I may use wheels constructed as shewn at
S¹, Figure 9.
'
I may use a steam chest for heating the converting chamber, and either of lead,
slate, earthenware, or wood lined with sheet lead. I may form a small cistern on
the top for water and acids.
The converting chamber may be made of common or glazed bricks set in cement,
and lined with cement or glazed tiles, or the said chamber may be made of slate or
wood lined with lead, or copper, tinned, or of any other material best suited for the
purpose, and the heat of said chamber may be regulated, if desired, at any time by
the use of steam.
I may use ammonia, at intervals, of any strength or quality best suited to the
process.
The pipes through which the gases and air pass into the converting chamber may
be made of lead, tin, gutta percha, india-rubber, copper, glass, or earthenware, or any
other known suitable substance, and in some instances I may use a meter for
measuring the gases and air before passing into the chamber, and can also use separate
vessels for the gases and air in the most convenient position for passing them into
the converting chamber.
I also use one or more condensers for the purpose of receiving the carbonic acid
gas from the gasometers, and I can pass the gas direct from the gasometers into the
converting chamber. When necessary I pass atmospheric air into these condensers,
which may be made of copper, lead, earthenware, slate, or wood lined with sheet
lead, and on the same I fix a pressure guage.
From the condensers above mentioned the gases and air pass into a receiver T,
Figures 8 and 9, before entering the converting chamber. On this receiver are
fixed a thermometer and a pressure guage. This receiver is kept at about two or
three degrees hotter than the converting chamber, so that the heated gases and air
enter more freely than when cold, it being very difficult to pass cold gases and air
into hot gases and hot air.
"
In connection with the apparatus above described I use a pump or pumps as
follows:-
Pump No. 1 is used for pumping the gases from the gasometers into the condensers,
and from them into the receiver T, before mentioned.
Pump No. 2 is used for pumping the gases, vapours, and air from the converting
chamber back into the gasometers. By these pumps I can pass the gases backward
and forward at pleasure, as best suited to the process.
Pump No. 3 is used for forming a vacuum in the receiver that is situated on the
top of the converting chamber; on the pipe connected to this pump is fixed a vacuum
guage.
<
This pump is also used for pumping air or water into the converting chamber, and

page_text: it may also be used for pumping the gases, vapour, and air backward and forward
from the chamber without passing back into the gasometers.
After the lead has been left sufficiently long in the converting chamber to
complete its conversion into white lead I commence cooling down the said converting
chamber, and taking away all gases and vapours as follows:-No. 1 pump is set to
work pumping in cold air; I then let out the hot water from the bottom of the
chamber; and as the hot water is passing out cold water is going into the chamber.
The hot water passes at once into a slate cistern buried in the ground; this cistern
has about four inches of cold water in the bottom, and the hot water pipe dips into
the said water, so that the hot water dives into such cold water, and thus prevents
any possibility of vapours escaping. This cold water cistern has double doors, made
air-tight, so that there may not be the slightest chance of the least escape. I then
put No. 2 pump to work pumping the cold air from the chamber that No. 1 is
pumping in; thus all spent gases and vapours are passed into a gasometer which is
connected with the receiver, into which all spent gases and vapours are passed.
No. 3 pump is then set to work for a final clearance, and also to pump water into
and thoroughly cleanse the receiver for all spent gases.
The gasometer before mentioned is made to rise and fall by means of a gutta
percha pipe, and when such gasometer is full, or at any convenient time, the vapours
are passed into the receiver for spent gases, into which steam is blown. From this
receiver all pass together into a pipe connected with the chimney; and in close
proximity to the end of this pipe superheated steam is blown, so that the deadly gases
and vapours are passed away harmlessly up the chimney without having the slightest
effect on those employed, and the converting chamber is then clear of all gases and
vapours, and as cold as when the process commenced.
I also use an air channel leading into the chimney from the outside of the building,
which channel increases the draught very much, so that every possible means may
be used to prevent the deadly scourge that is so common in the old method of
manufacturing white lead.
Having thus fully described the said Invention, and the manner of performing the
same, I wish it understood that I claim,-
First. The combination, with the melting pan divided into compartments, of the
jackets D, E, as above described and for the purpose set forth.
Second. The method of producing granulated lead, as above described.
Third. The construction of moulds for producing lead in such a shape that the
most advantageous action of the vapours will be secured, as above described.
Fourth. The use of leaden pots for containing the acids and water in the converting
chamber, as above specified.
Fifth. The combination with the converting chamber of the receptacle for the acids
and water, the pipe for heating the same, the means of indicating the heat within
such chamber, and the fans, as above set forth and for the purposes specified.
Sixth. The carriage provided with means for freely moving it in and out of the
converting chamber, as above described.
Seventh. The worm or worms L, in combination with the converting chamber and
water and acid reservoir, as herein described and for the purposes set forth.
Eighth. The glass roof within the outer roof of the converting chamber, as above
described and for the purposes specified.
•
Ninth. The chamber O and globe or globes P in combination with the converting
chamber, as above set forth and for the purposes specified.
Tenth. The means for keeping up the required heat of the water and acids by gas,
as above set forth.
Eleventh. The receiver T, in which the gases are heated previous to entering the
converting chamber, as above set forth and for the purpose specified.
Twelfth. The receiver Q and its connections in combination with a steam jet, as
above set forth and for the purposes specified.
Thirteenth. The pumps operating in connection with the converting chamber, as
above described.

page_text: Fourteenth. The process and apparatus for producing white lead, as above set
forth.
In witness whereof, I, the said William Thompson, have hereunto set my
hand and seal, this 11 day of April, in the year of our Lord One
thousand eight hundred and seventy-eight.
WILLIAM THOMPSON. (LS.)