CERTAIN IMPROVEMENTS IN THE MANU-. FACTURE OF WHITE LEAD
Year: 1839

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
FLUDE, of Liverpool, in the County of Lancaster, Chemist, send greeting..
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twentieth day of July, in the third year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the
said 'Charles Flude, my exors, admors, and assigns, Her especial licence, full
power, sole privilege and authority, that I, the said Charles Flude, my exors,
admors, and assigns, and such others as I, the said Charles Flude, my exors,
admors, or assigns, should at any time agree with, and no others, from time
to time and at all times during the term of years therein expressed, should
and lawfully might make, use, exercise, and vend, within England, Wales, and
the Town of Berwick-upon-Tweed, and also in all Her Majesty's Colonies and
Plantations abroad, my Invention of "CERTAIN IMPROVEMENTS IN THE MANU-.
FACTURE OF WHITE LEAD;" in which said Letters Patent is contained a
proviso that I, the said Charles Flude, shall cause a particular description of
the nature of my said Invention, and the manner in which the same is to be
performed, to be inrolled in Her said Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said in
part recited Letters Patent, as in and by the same, reference being thereunto
had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles Flude, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are fully shewn, set forth,
and ascertained in and by the following description thereof, reference being
had to the illustrative Drawings hereunto annexed, that is to say :-
In Drawing No. 1, Figure 1 is a plan, and Figure 2 a transverse section, of
an apparatus for the manufacture of white lead constructed on the principle
of my said invented improvements, and for the purpose of carrying the same
into effect. B and E are two wooden or other vessels (technically known
by the name of backs), for holding a solution of lead, about seven feet square
and five feet deep. These backs should be strongly constructed and lined with
stout sheet lead. The backs are heated by steam conveyed through a coil of
strong pipe of about two inches diameter in the bore from the boiler A. The
coil may be made either of lead, or tin, or pewter, or any other suitable material,
but I prefer lead or a compound of fourpar ts of lead with one part of tin (by
weight). The coil is made to pass perpendicularly to the bottom of the back,
and then transversely backward and forward, as shewn in the Drawings, Fig. 1;
the end of the coil passes through the sides or bottom of the vessels, as shewn
at M. The condensed water may be collected in a vessel suitably placed to
receive it, and used for washing the precipitated white lead, or it may be conveyed
back to the boiler by any of the usual modes, but if this be done the boiler
must be provided with a safety valve; or in lieu of the steam pipes, a double
vessel may be employed, the steam circulating between them, as in the steam
jacket pans used in pharmaceutical laboratorys, see Figure 1. G, H, are two
gas vessels or receivers working in corresponding tanks after the manner of
the gasholders employed at the works of the different gaslight companies;
K is a pipe (with a biforked termination) which conveys carbonic acid gas to
the receivers from the generator or retort L, one forked leading to the receiver
G, and the other to the receiver H, as shewn in the plan. A rod is connected
with the top of each receiver to a lever valve or cock, so as to open or shut
off the communication with the retort or generator as the vessel rises and falls
in the tank, or in lieu of the lever, internal valves may be used, as shewn at
2 N is a pipe for conveying steam into the gas pipe K, with a cock O; by
which the supply may be regulated. A solution of acetate of lead (or sugar
of lead), obtained by any known process, is first introduced into the vessel B.
The steam cock D being shut, the steam is turned on at c, whereby the
solution becomes heated; oxide of lead (or litharge) is then added at intervals,
stirring the solution each time with a wooden spatula or other suitable

page_text: instrument until it is found that the solution will take up or dissolve no more
litharge or oxide of lead. The solution is then in the state known to chemists
as "di-acetate" of lead, containing two proportions or about two twenty-fourth
parts of oxide of lead to about fifty-one parts of real acetate acid. The
solution is then allowed to settle, leaving a small portion of oxide of lead
undissolved at the bottom, and when sufficiently settled, which will be best
effected by keeping the solution at about one hundred and twenty to one
hundred and fifty degrees of heat (Fahrenheit), the solution is drawn off by
cocks in the side of the vessel, or by any other suitable means, and transferred
to the vessel E. The steam cock C is then shut off and D opened (F being
shut), and the solution kept at about the same temperature as before. The
retort L, heated by the fire below, is charged with about twenty to twenty-four
pounds of charcoal, coke, or anthracite, or a mixture of either, for every
one hundred and twelve pounds of litharge previously dissolved in the
solution of acetate of lead in the back B. The cock O being partially
opened, a small quantity of steam passes from the boiler into the gas pipe
K, a portion of which condenses and descends into the retort L, where
it is again converted into steam and mixes with the carbonic acid and the
carbonic oxide liberated by the charge in the retort, while at the same time
a portion of the carbonic oxide is converted thereby into carbonic acid.
The steam pipe N is laid with an inclination towards the boiler to
convey back thereto the greater part of the condensed water. As much of
the coil of steam pipe as is not intended to be immersed in the solution
of lead should be protected as much as possible by yarn, flannel, or other slow
conducting substances to prevent the loss of heat by radiation. The gasses
and steam giving off from the retort then pass through the tank by the pipe k,
and enter the receiver Number 1, which is counterpoised by a weight or chain
passing over a pulley fixed above in any convenient position. The receiver as
it rises shuts off connection with the retort by means of the lever valve and
rod before described. Pressure is then applied to the receiver or gasholder
by a hand lever fixed above, or by any other suitable means. The carbonic
acid gas is thereby propelled through the pipe I, which is carried to the
bottom of the back E. This pipe is perforated at the bottom by several
small holes of about three-sixteenths of an inch in diameter, by which means
the carbonic acid is diffused in and through the solution. The connection
between the retort and receiver Number 1 being shut off, the gas passes
into the receiver Number 2, which when full becomes itself shut off by the
lever valve, and the gas passes again into Number 1. The valve being

page_text: opened by the descent of the gasholder Number 2, is then subjected to
pressure, and the gas passes through a perforated pipe into a solution as before.
The process of injecting gas into the solution is thus made continuous, one
receiver filling as the other is emptying. The most convenient way of regu-
lating the reciprocating action of the gas vessels is to connect them to the
opposite ends of a lever sustained and turning on its centre, as in the case of a
scale beam. A cock is shewn at the bend of the ejection pipe I to let off from
time to time any condensed water that might otherwise impede the passage of
the gas. The carbonate of lead formed by this preceding process subsides to
the bottom of the vessel E, and to prevent its choking the apertures in the pipe
I, the solution is kept stirred by a wooden spatula, and the steam occasionally
blown through the ejection pipe by turning on the cock F, which effectually
clears the apertures from obstruction. To ascertain when the precipitating
process is complete, I make use of the following means:-A small portion of
the solution being removed from the back E in a test glass or other suitable
vessel, a jet of gas is forced through the same by applying the glass to the
small cock shewn at P, and when no further precipitation is produced thereby
the gas process is stopped, and the solution allowed to subside, still keeping it
about one hundred and twenty degrees of heat by means of the regulating cock
D. When the precipitate has subsided, the supernatant solution of acetate of
lead is drawn off and returned to the back B, when it is employed to dissolve
a fresh portion of oxide of lead as at first, and the precipitate in E having been
removed to a drainer and washed, the solution of sub-acetate of lead is then
transferred from the dissolving back B to the precipitating back E, after which
the process goes on as before. If the condensed water of the boiler is em-
ployed for washing the precipitated carbonate of lead, proper precaution must
be taken to insure its purity, and all the pipes through which it passes should
be of lead or pewter. The pressure of the steam may in this case be obtained
by causing the ends of the worm pipes M to dip into a greater or lesser
column of water. The quantity of steam admitted into the gas pipe K is
regulated by the cock O, and is ascertained by the jet cock P, which, when
turned on, should shew very little aqueous vapours.
Another improved form of apparatus for precipitating the solution of sub-
acetate of lead by means of carbonic acid gas is shewn in Drawing No. II.,
Figure 3. The backs B and E are constructed as before, but the precipitating
back E has the lead lining securely attached by means of screws or lead straps
or other adequate means to the sides of the back; it is also furnished with a
lid made air-tight, and a man-hole and lid (as shewn at Q) screwed down (as.

page_text: in a steam boiler), which is for the purpose of giving access to the interior of
the back when it is required to clean it out, or for any other purpose. Two
air vessels and tanks are shewn in the floor above, similar in construction to
the reciprocating gasholders and tanks before described, except that only one
pipe is necessary to each vessel passing through the water, and terminating in
a valve opening upward (as shewn at R, R.) These pipes communicate with
an exhaustion pipe (about one and a half inches in diameter) passing through
the air-tight lid of the back E, to which it is secured by a flange. The
manner of using this last-described apparatus is as follows:-The solution is
made as before described in the back B, and transferred as before to back E,
leaving a space of about nine inches between the surface of the liquor and the
lid. The most convenient mode of transferring the solution is to pump it from
B through the man-hole Q by means of a fixed pump X placed between the
two backs, having a suction pipe branching off to each of the backs, and
furnished with two stop-cocks to shut off the connexion with the back into
which the liquor is to be transferred. The man-hole being now covered and
made tight, the air vessels are alternately raised and depressed as before
described, by which means an exhaustion or vacuum is obtained in the space
above the liquor in the back E. The air having been discharged through the
top valves S, S, of the air vessels, and the pressure being thus removed from
the surface of the solution, the carbonic acid gas forces itself through the
solution (through the gas pipe N) and becomes absorbed, while the car-
bonic oxide and atmospheric air which enters with it are withdrawn, and
expelled by the air vessels above. The process is known to be completed by'
drawing off a small portion of the solution through the small cock shewn at
V, and testing it with a solution of carbonic acid in water. When no further
precipitate is seen to be produced thereby the process is stopped, the solution
is allowed to settle, the supernatant liquor pumped back into B, and the white
lead deposited racked out through an opening W at the bottom, which is
covered when working with a pewter plate screwed on; or, in lieu of the air
vessels above described, the vacuum may be produced by a steam pipe,
cylinder, pump, or other suitable means. Instead of the gas retort herein-
before described, I sometimes employ in lieu thereof two small furnaces,
burning charcoal, coke, anthracite, or a mixture of either. The air passing
between the bars converts the vapour into carbonic acid gas, as before
explained. Small air holes may also be made through the fire-doors, fur-
nished with slides (for adjustinent), and a steam pipe furnished with a stop-
cock is introduced into any convenient part of the gas pipe N, as before

page_text: described. A branch pipe or flue is also shewn at T, which pipe communi-
cates with a chimney, and is furnished with a damper, to regulate or shut off
the draught. The use of this pipe is to obtain the necessary draught at first
lighting the fires, after which it may be shut off. I prefer making the gas
fires about eighteen inches by twenty-four inches in the grate, and the re-
ceivers or air vessels of about ten cubic feet capacity, working with about a
two-foot stroke. Small casks answer very well for this purpose, one end being
removed, and the other furnished with a valve opening upward to discharge
the air.
A third improvement in the manufacture of white lead is embodied in the
apparatus represented in Figure 4. This improvement consists in exposing
metallic lead to a powerful heat in an iron retort or pan A, and passing over
the surface of and through the same a strong blast of air or steam (B), so as
to cause a volatilization of the lead or its oxide, which passes out in its
volatized state through an opening (C) opposite to the blast, into a chamber
(D), about twenty-five feet long by eight feet broad, and eight feet high,
which chamber is filled with carbonic acid gas by means of the pipe or
opening E. The bottom of the chamber D is covered with water to assist the
condensation of the vapours, and the uncondensed portions pass through an
opening F into another chamber G, similar to the first, which chamber must
be furnished with a large valve opening upward, as shewn at H. The cham-
bers D and G must each be furnished with a man-hole, to clear out the
carbonate of lead formed therein. A series of such receivers or chambers
may be used, but two, if sufficiently large, will be enough for about a ton of
lead at a charge distributed among three or four retorts or pans. The
chambers are formed of bricks set as close as possible; and if a pan is used
instead of a retort, it should be arched over with fire-bricks set as close as
possible. T is an iron funnel to supply the retort with melted lead. The
opening II may communicate with a chimney to produce a draught; and in
that case the valve will not be required.
And having now described my said invented improvements, and the manner
in which the same are to be performed, I declare that I do not claim as of my
Invention the obtaining of carbonic acid gas from charcoal, nor the pro-
ducing of carbonate of lead or white lead from a solution of sub-acetate of
lead by precipitation with carbonic acid gas; but that what I claim as of my
Invention is,―
First, the peculiar method or process herein-before described of con-
verting oxide of lead or litharge into a solution of subacetate of lead, and

page_text: of producing therefrom, by precipitation with carbonic acid gas, white lead.or
carbonate of lead.
Second, the employment in the manufacturing of white lead of steam in
combination with carbonic acid gas for precipitating solutions of lead.
Third, the employment, in the manufacture of white lead, of the method
herein-before described of collecting and injecting the carbonic acid gas by
means of reciprocating hydraulic gasholders, whether that method is used
along with the rest of my said improved methods or any of them, or used
separately.
Fourthly, the manufacture of white lead from the combination of vapours of
lead, or lead in a volatized state, with carbonic acid gas.
:
And, lastly, the three descriptions of apparatus for the manufacture of white
lead herein-before described, each considered in its generality and entirety,
disclaiming the parts of each apparatus taken separately (excepting always the
reciprocating hydraulic gasholders herein-before separately claimed), and
claiming the parts of each apparatus only in as far as they are in such appa-
ratus newly combined and arranged, for the purpose of carrying into effect my
said invented improvements in the manufacture of white lead, one or other of
them.
And such my said invented improvements in the manufacture of white lead
being, to the best of my knowledge and belief, entirely new, and never before
used within that part of Her Majesty's United Kingdom of Great Britain and
Ireland called England, Her Dominion of Wales, Town of Berwick-upon-
Tweed, or in any of Her said Majesty's Colonies and Plantations abroad, I do
hereby declare this to be my Specification of the same, and that I do verily
believe this my said Specification doth comply in all respects fully and without
reserve or disguise with the proviso in the said herein-before in part recited
Letters Patent contained; wherefore I hereby claim to maintain exclusive
right and privilege to my said Invention.
In witness whereof, I, the said Charles Flude, have hereunto set my
hand and seal, this Eighteenth day of January, One thousand-eight
hundred and forty.

page_text: AND BE IT REMEMBERED, that on the Eighteenth day of January,
in the year of our Lord 1840, the aforesaid Charles Flude came before our
said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute made for that purpose.
Inrolled the Twentieth day of January, in the year of our Lord One
thousand eight hundred and forty.