AN IMPROVED PROCESS AND APPARATUS FOR THE MANUFACTURE OF WHITE LEAD
Year: 1883

page_text: LETTERS PATENT to Herbert John Haddan, of the Firm of Herbert and
Company, Solicitors of Patents, of 67, Strand, in the City of Westminster,
Civil Engineer for an Invention of AN IMPROVED PROCESS AND APPARATUS
FOR THE MANUFACTURE OF WHITE LEAD a communication to him from abroad
PROVISIONAL SPECIFICATION left by the said Herbert John Haddan at the
Office of the Commissioners of Patents on the 31st December 1883.
HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Solicitors of
Patents, of 67, Strand, in the City of Westminster, Civil Engineer,
" AN
"
IMPROVED PROCESS AND APPARATUS FOR THE MANUFACTURE OF WHITE LEAD,"
a communication to me from abroad by F. Schmoll, of Cologne, in the German
Empire,
The process for the production of white lead hereinafter described has the
advantage that it produces no dust, which during the various operations of
manufacture and especially at the removal (collection) of the finished product
from the oxidizing chambers, presents so many dangers to the health of the
workman.
Owing to the construction of the oxidizing chambers which may be set in
operation separately, or together if placed side by side, and owing to the arrange-
ment for emptying these chambers, the workmen will no longer be placed in direct
contact with the dry white lead.
The process works as follows:
The lead is formed into thin plates either by casting or rolling, or into a spongy
mass of thin shavings or threads in any other suitable manner and then placed on
boards or latbs side by side and superposed or suspended in the oxidizing chambers,
in such a manner that the latter are entirely filled. The boards or laths may be
supported in the chambers by a wooden frame work.
After the chamber is filled and closed vinegar is evaporated in a closed copper
boiler and the vapours thus formed escape through a pipe underneath the lid of the
boiler into a flue situated under the floor of the oxidizing chamber.

page_text: In another apparatus provided with a fire-grate removable cover and air flues
(placed side by side and at different levels) carbonic acid is developed by the
combustion of coke, or by heating lime stone or marble or by other known means
which carbonic acid is also conducted in the above mentioned flue.
In the latter the carbonic acid mingles with the vapours of vinegar, and the
mixture penetrates through stone pipes into the oxidizing chamber, where it is
regularly distributed over the whole space and oxidizes the lead contained in the
same.
During the period of oxidation the vapours of vinegar are continuously introduced
into the chambers, while the carbonic acid is only admitted periodically and in
proportion as required in order to obtain a complete transformation of the metallic
lead into basic carbonate of lead (white lead).
Openings are provided in the front and back wall of the chamber, and are covered
with glass, in order to watch the progress of the operation.
After complete oxidation the white lead still suspended from the boards is
removed by means of a jet of water introduced through the roof and through
the sides of the chamber. During the period of oxidation the top openings are
closed.
After the white lead has been washed away suitable apertures in one of the side
walls of the chamber are opened. The white lead, which has been transformed
into a semi liquid mass by the washing, runs on the inclined floor and escapes from
the chamber through a channel placed before the side openings, into suitable tanks.
To prevent the unoxidized parts of the lead from passing into the said channel,
copper screens or sieves are placed before the side openings, and to prevent the
outlets from being choked, a jet of water is directed on the same.
After having allowed the white lead to settle in the tank the superincumbent
water is removed by a syphon or any other suitable means, and the semi liquid
white lead is then pumped into an apparatus suitable for removing the particles of
lead still contained in the mass.
The white lead thus prepared is further separated from water by means of presses
or suitable filtering apparatus, subsequently it is dried and pulverised.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Herbert John Haddan in the Patent Office on the 30th June
1884.
HERBERT JOHN HADDAN of the Firm of Herbert and Company, Solicitors of
Patents, of 67, Strand, in the City of Westminster, Civil Engineer,
"AN
IMPROVED PROCESS AND APPARATUS FOR THE MANUFACTURE OF WHITE LEAD,"
a communication to me from abroad by F. Schmoll, of Cologne, in the German
Empire,
The process for the production of white lead hereinafter described has the
advantage that it produces no dust, which during the various operations of
manufacture and especially at the removal of the finished product from the
oxydizing chambers, present so much danger to the health of the workmen.
Owing to the construction of the oxydizing chambers, which may be set in
operation separately, or together if placed side by side, and owing to the method of
emptying these chambers, the workman will no longer be placed in direct contact
with the dry white lead.
The process is as follows:
The lead is cast or rolled into thin sheets or formed into a spongy mass of '´
shavings or threads, by planing or in any other suitable way, and then placed on
boards or laths a, a, .... arranged side by side and at different levels, in the
oxydizing chamber A (figs 1 and 2, sheet I), in such a manner, that the latter are
entirely filled with such boards or laths, carrying the lead and supported by the
cross bars or beams b, b, .. of a wooden frame work.
The special construction of the wooden frame work and the arrangement of the
apparatus is illustrated on sheets I and II, Figs 1 to 8, of which Fig. 1 is a vertical
section along line A-B of Fig. 3,-Fig. 2 a vertical section along line C-D of
Fig. 3, Fig. 3 a horizontal section along line E-F of Fig. 2, and Fig. 4 a
horizontal section along line G-H of Fig. 2.
After the chamber has been filled and well closed, vinegar is evaporated in a
closed copper boiler, V, provided with a fire place, and the vapours thus generated
escape through a pipe above the lid of the boiler and are conducted into a flue K
situated under the floor of the oxidizing chamber. Another apparatus, B, is repre-
sented on sheet II of which Fig. 5 is a side view, Fig. 6 a plan, Fig. 7 a vertical
section and Fig. 8 a horizontal section.
This apparatus comprises a hearth with a fire grate, a removable cover, and air
flues arranged radially and at different levels. Carbonic acid is developed by the
combustion of coke, or by heating lime stone or marble, or by other known
means, which carbonic acid is also conducted into the flue K, of the apparatus
(figs 1 to 4).
In the flue K the carbonic acid mingles with the vapours of vinegar, and the
mixture penetrates through stone ware pipes r, r, ... into the oxidizing chamber
where it spreads uniformly over the whole space and oxydizes the lead contained
in the same. During the period of oxidation, vapours of vinegar are continuously
supplied to the chamber, while the carbonic acid is only admitted periodically and
in the proportion required to obtain a complete transformation of the metallic lead
into basic carbonate of lead, (white lead).
The openings C C of the front and back wall of the chamber are covered with
glass in order to watch the progress of the operation and to ascertain whether it is
necessary to introduce a larger or smaller quantity of carbonic acid, and at shorter
or longer intervals. After complete oxidation, the white lead still adhering to the

page_text: laths is removed by means of jets of water introduced through the roof and
through the sides of the chamber. Four openings o, 0, 0, 0, in the roof are
generally sufficient; they are closed during the period of oxydation.
After the white lead has been washed away, the apertures Z, Z, in one of the
walls of the chamber are opened. The white lead, which has been transformed
into a semi-liquid mass by the washing, runs on the inclined floor and escapes from
the chamber through a gutter R placed in front of the side openings into collecting
tanks. To prevent the unoxidized parts of the lead from passing into the gutter R,
copper screens or sieves are placed inside before the said openings, and to prevent
the outlets from being choked by the semi-liquid white lead, a jet of water is
directed on the openings. After having allowed the white lead to settle in the
collecting tank, the superincumbent water is removed by a syphon or any other
suitable means, and the semi-liquid white lead is then pumped into a slime
apparatus or similar purifier in which it is edulcorated and separated from
particles of lead which may still be contained in the mass. The white lead thus
prepared is further separated from water by means of presses or suitable filtering
carried out
apparatus and subsequently dried and pulverised. The pulverizing
in apparatus specially constructed for this purpose and which allows no dust to
excene