IMPROVEMENTS IN THE MA- BUFACTURE OF CARBONATE OF LEAD
Year: 1847

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JEAN
MARIE FOURMENTIN, of New Bridge Street, Blackfriars, Gentleman; send"
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-second day of May, in the tenth year of Her reign, did,
for Herself, Her heirs and' successors, give and grant unto me, the said Jean
Marie Fourmentin, Her especial licence, full power; sole privilege and authority,
that I, the said Jean Marie Fourmentin, my executors, administrators; and
assigns, and such others as I, the said Jean Marie Fourmentin; my executors;
administrators, 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 mentioned,
should and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, and in all Her Majesty's
Colonies and Plantations abroad, and in the Islands of Jersey, Guernsey;
Alderney; Sark, and Man, my Invention of "IMPROVEMENTS IN THE MA-
BUFACTURE OF CARBONATE OF LEAD;" in which said Letters Patent is con-
tained a proviso obliging me, the said Jean Marie Fourmentin, by an
instrument in writing under my hand and seal, particularly to describe
and ascertain the nature of my said Invention, and in what manner the
same is to be performed, and to cause the same to be inrolled in Her
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

page_text: in and by the same, reference being thereunto had, will more fully and at
large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Jean Marie Fourmentin, do hereby declare that the nature of my said Inven-
tion, and the manner in which the same is to be performed, is particularly 5
described and ascertained in and by the following description thereof, refe-
rence being had to the Drawings hereunto annexed, and to the letters and
figures marked thereon (that is to say) :—
My Improvements in the Manufacture of Carbonate of Lead, commonly
called white lead, consist :-
.1
Firstly, in the application of carbonic acid. to a mixture of soda and
oxichloride of lead, obtained by the action of chloride of sodium or sea salt
upon protoxide of lead, so as to decompose the said oxichloride of lead,
whereby insoluble carbonate of lead is produced, and a solution of chloride
of sodium remains; and,
Secondly, my Invention relates to an improvement in the method of
manufacturing carbonate of lead by first separating the soda. from the oxi-
chloride by washing, and, after decomposing the oxichloride. by the action of
carbonic acid, introducing carbonate of lime at a boiling temperature. to
complete the operation, thus producing a. more expeditious and economical
reaction, and. leaving the soda in a fit state to be used for other purposes.
The principles and details of my Invention are as follows:-
First, on submitting oxichloride of lead,. either dried at a low temperature
and reduced to power or diluted, with water to the action of carbonic acid, it
will be decomposed into chloride, carbonate, and oxide of lead, or litharge;
and if the action of the. carbonic acid be continued during a sufficient. length of
time, the oxide will become completely carbonated, so that there. will only.
remain chloride and carbonate. of lead.
Secondly, on submitting. chloride. of lead to the action of an alkaline
carbonate, or carbonate of lime, and using water as a medium, an alkaline
chloride or chloride of calcium and carbonate of lead will be. produced. The
final result of these two successive reactions is therefore an alkaline. chloride or
chloride of calcium in solution, and a precipitate of carbonate of lead, which, by
calcination, may be easily converted again into oxide of lead.
Thirdly, if the oxichloride of lead be mixed with a solution of an alkaline
bicarbonate, in, equivalent quantities, this, latter will first react in the same
manner as the carbonic acid, producing chloride, carbonate, and. oxide of lead;
but the remaining alkaline. carbonate reacting upon the chloride, forms a second
equivalent of carbonate of lead, the final result being alkaline chloride. in

page_text: solution, and-a-precipitate containing two equivalents of carbonate of lead
mixed with the oxide of lead in excess, which may be afterwards submitted to
the action of carbonic acid. It will therefore be seen that the mode of action
of the carbonate comprises the reactions mentioned. in the two preceding
5 paragraphs. Two distinct operations are therefore necessary in order to
convert oxichloride of lead into a carbonate: first, decomposition into chlo
ride, carbonate, and oxide of lead, or into chloride and carbonate; and,
secondly, decomposition of the carbonate of lead into carbonate.
.
First Operation. Decomposition of the oxichloride of lead by carbonic
acid.-I. shall divide the description of this operation into three heads:
first, the production of carbonic acid; second, the carbonating apparatus;
and, third, as to condition of the oxichloride most favorable to the action of
the carbonic acid.
:
First, production of the carbonic acid.-Besides being produced by the
action of an, acid; upon carbonate of lime, which is to expensive à process,
carbonic acid may be obtained in large quantities either by the combustion of
charcoal, anthracite, or coke, or by. the calcination of carbonate of lime mixed
.with, one of those combustibles,, the latter, mode being generally the most
advantageous. In these two methods the coke and anthracite must be free
from all sulphurous matter, otherwise the gas, in order to purify it, must be
washed in milk of lime. It will be necessary to be very careful in the manu-
facture of the coke, and to pass the gas through a sufficiently spacious
chamber, similar, to the condensing chambers of certain kinds of mines, from
which it passes direct to the carbonating apparatus or cylinders, after having
deposited in the chambers any solid matter, which it may have carried along
with it..
** "
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.
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.....
Second, carbonating apparatus.-A. force pump or a archimedean screw is
generally used for forcing the gas through the carbonating liquid; but as, in
that case, the oxichloride is not dissolved,, but merely held in suspension, the
reaction is more difficult, and consequently a large quantity of gas. would
escape without reacting .unless the column through which the gas passes..were
greatly.lengthened.. Although various kinds of apparatus might be employed
for the above purpose, I prefer the one I am about to. describe, and which is
represented in, the, accompanying Drawings, as it possesses many..advantages.
over those already devised. It consists of a series of. fixed. cylinders, through
which is carried a horizontal. shaft.. furnished with radial beaters. These
beaters.are..made to revolve at the rate of about four or five revolutions per
minute, so as to.continually agitate the oxichloride, which is suitably diluted,

page_text: and let into the cylinders in sufficient quantity to about half fill them. By
this means a fresh surface of the oxichloride is presented constantly to the
action of the carbonic acid, which passes without pressure from cylinder to
cylinder, so that the current of gas first entering the cylinder in which the
carbonation is most complete passes successively through all the others in the 5
order in which they were filled, making its exit by that cylinder which last
received its charge. The exit gas is then conducted into a vessel which con-
tains the solution of caustic soda obtained in converting the oxide of lead into
oxichloride, in order to carbonate the soda and to precipitate the oxide of lead
This vessel is also furnished with an
which may be dissolved therein.
agitating apparatus, similar to that of the fixed cylinders before mentioned.
Lastly, the gas which has not been absorbed passes up the general chimney of
'the manufactory, whereby a draft will be created in the furnace where the
carbonic acid is generated, independently of that produced by the absorption of
the gas in the carbonating apparatus. In the accompanying Drawing the appa-
ratus is shewn as consisting of three cylinders (the vessel for containing the alka-
line solution not be represented) ranged in a straight line. It will however be
understood, that the number, arrangement, and dimensions of the cylinders or
their appendages may be varied according to the scale on which the manufac-
ture is carried on, or the general arrangement of the works. The diameter of
the tubes for conducting the gas to the cylinders must be such as to allow
a quantity of gas to circulate in the apparatus sufficient to decompose and
of
saturate all the material which is furnished in a given time in the progress
the other operations. When the carbonate of lead is intended to be used as
ceruse, it is absolutely necessary to avoid the use of iron in the construction of
the cylinders, the presence of which would cause the product to assume a
reddish tint. Copper also must be avoided, as it would render it green;
if the carbonate of lead is intended for calcination, iron and copper may
employed without any great inconvenience, although lead and wood are fa
preferable whenever they can be used. Figure 1 is an elevation of th
apparatus; Figure 2 is a plan view of the same; and Figure 3 is a lon
gitudinal vertical section of the apparatus. A, A1, A2, are three cylinder
fixed in the framing B, B; C is a shaft which has its bearings in the end
of the cylinders, and is caused to rotate by any motive power. Upon th
shaft radial beaters D, D, are mounted, (as shewn in the cross section
Figure 4) one set for every cylinder. E, E, are funnel-shaped openin
in the top of the several cylinders. A to admit of the charges being poure
therein. These openings are each closed by a cover F, which fits into
lip or gutter formed at the bottom edge of the funnel-shaped openin
.bu
b

page_text: and render the cylinder air-tight. The cylinders are connected toge-
ther by a horizontal pipe G, having vertical branches which severally enter
their respective cylinders. H is a pipe leading from the cylinder A to the
cylinder containing the ley, as before mentioned; it has also branch pipes to
the cylinders A' and A. K is a third horizontal pipe, and is intended to
connect the first and the last of the series of cylinders together. L, L', are
two short pipes placed between the cylinders, and intended to connect them
all together. These pipes are severally provided with stopcocks (as shewn in
the Drawing, and marked a, a¹ to a³ respectively) for the purpose of regu-
lating the flow of the gas. 6, 6, are test cocks for ascertaining the progress of
the operation. The mode of working the apparatus is as follows:-Suppose
the cylinders A, A1, A2, to be charged successively according to their order, the
cocks a, a, a, and a only are open; the gas passes along the pipe G, through
the cock a into the cylinder A, thenco through the cock a³ of the pipe L' into
the cylinder A'; it then passes off through the cock a* of the pipe L', and
enters the cylinder A; from which it escapes by the cock a' into the pipe H,
leading to the receptacle for the alkaline solution. When the operation is
completed in the cylinder A, communication with it is to be cut off by shutting
the two cocks a and a³, after opening the cock a¹; the exit pipe O at the
bottom of the cylinder A is then opened, and also the charging aperture E.
The movement of the radial beaters facilitates the flow of the liquid through
the pipe O, and water may be poured on the beaters for the purpose of
washing them, after which the exit cock O is shut, and the cylinder is
recharged. The opening E is now closed, and the cylinder A is put in com-
munication with the cylinder A by opening the cock a³ in the pipe K¹. The
cylinder A thus becomes the last of the series to receive the gas, which is then
allowed to pass out of the apparatus by the cock as of the pipe H to the
cylinder containing the alkaline solution, the cock a having been opened at:
the same time that the cock a' was closed. For the purpose of discliarging and
charging the cylinder A¹, the cocks a¹ and a' are closed after having opened
a; and when the charging operation is completed the cocks a³ and a° are
opened and a is shut, and so on for the other cylinders. Figure 5 shews a
mode of constructing the cylinders whereby their upper half may be removed,
if required, to admit of ready access to the interior for cleaning.
Third, the condition of oxichloride most favorable to the action of car-
bonic acid.-Oxichloride of lead, when dried at a low temperature, under
212° Fahrenheit, and pulverized, may be decomposed by carbonic acid gas;,
but, independently of the expence of dessication and grinding, the danger to
which the workunan are exposed in operating upon large masses of compounds.

page_text: of lead in a pulverulent state renders it preferable to cause the carbonic acid
to act on the oxichloride in the presence of water, as the reaction takes place
sooner under those circumstances. The oxichloride must therefore be suffi
ciently diluted to admit of the gas passing easily through it, which is effected
by means of a forcing apparatus, and in order also that it may be easily
stirred when no pressure is applied. Care must, however, be taken not to add
more water than is absolutely necessary, that the quantity of fluid may not
bè so much increased as to prevent its being easily stirred in the cylinder
apparatus; or require too much power when the forcing apparatus is employed.
Second Operation. Decomposition of the chloride of lead by carbonate of
lime, or by an alkaline carbonate.-Firstly, decomposition by carbonate of
lime: When the action of the carbonic acid on the oxichloride is completed
(which is ascertained by agitating a portion of the mixture in a small vessel,
and filtering and boiling the solution, when, if carbonic acid is disengaged,
and a white precipitate formed, the decomposition of the oxichloride is com-
pleto and all the oxide of lead carbonated), the mass is poured into a leaden
boiler, and a quantity of finely powdered carbonate of lime is added, equivalent
to the quantity of salt decomposed by the oxide of lead in the first instance
(which quantity must first be ascertained by the alkilimeter, but may afterwards
be averaged by ascertaining the quantity of soda obtained at each operation,
and deducting from it the quantity of carbonate of lime to be added, allowance
being made for that introduced in the water); water is then added, and the
liquid is boiled during a time varying from half an hour to four or five hours;
according to the quantity operated upon, and the decomposition of the chloride
of lead will be complete, which may be ascertained by treating a small quantity
of the filtered fluid first with ammonia and then with hydrosulphate of ammonia;
if the operation is complete, no precipitate will be produced. The reaction
between the oxichloride of lead and carbonate of lime might also be produced
at an ordinary temperature by agitating the mixture, and the two operations
may be combined by introducing the carbonate of lime into the apparatus at
the same time as the oxichloride; but the reaction is so slow when in a cold
state, and there would be so much time lost (as the operation would take
several days instead of half an hour), that it would be impossible to carry on
the manufacture on a large scale; besides, as bicarbonate of lead, slightly
soluble, might be formed, there 'would necessarily be a portion lost in the
water with which it was washed, whilst by boiling, the bicarbonate is decom-
posed and converted into carbonic acid, which is disengaged, and into car-
bonate, which is precipitated. Lastly, the addition of chalk or carbonate of
lime in the carbonating apparatus, by augmenting the mass to be stirred;

page_text: would necessitate the employment of larger apparatus and greater power. I
would here observe, that even if the temperature of the gas should be suffi-
ciently high to heat the mass to the boiling point, as the absorption of the
carbonic acid takes place more readily at the ordinary temperature than when
the fluid is heated, it would be advisable to reduce the temperature of the gas
before passing it into the carbonating apparatus. When the carbonation is
completed the carbonate of lime may be added, and the mixture heated to
the boiling point.
in
Secondly, decomposition by carbonate of soda.-When the carbonate of
lead is to be calcined, the greater or less purity of the carbonate of lime is
of no importance; but if the carbonate of lead is intended for consumption
as a pigment, the carbonate of lime must be free from oxide of iron, or at least
contain so little that the white lead produced may not be colored thereby. If,
therefore, the carbonate of lime could not be obtained sufficiently pure by
suitable washing, it would be necessary to employ carbonate of soda to decom-
pose the chloride of lead, and the two operations would be united in one;
fact, the soda formed by the reaction of the chloride of sodium upon the oxide
of lead being necessarily equivalent to the chlorine of the oxichloride, it will
only be necessary to introduce immediately into the carbonating apparatus the.
mixture of soda and oxichloride. The carbonic acid will act simultaneously
by decomposing the oxichloride and carbonating the soda, so that the car-
bonate of soda and chloride of lead reacting upon each other as they are
formed, the decomposition will be complete. When the solution, after being
filtered and boiled, ceases to redden litmus paper, there would then only remain
some oxide to carbonate, and the chloride of sodium employed will be repro-
duced, and may be again employed any number of times; for this purpose it
will only be necessary to concentrate the last washings. It will now only
be necessary, in order to render the carbonate of lead fit for calcination,
to separate the chloride in solution from it by washing; but if it is to
be used as white lead, it will be necessary to separate from it a portion
of litharge which has not acted upon the salt, and which still retains its
peculiar color. As its particles are much heavier than those of the ceruse,.
they may easily be separated by levigation, either in ordinary vessels, or
vessels with several compartments, similar to those used in white lead or
massicot manufactories. The ceruse is then strained, packed, and dried in the
ordinary manner. The residuum of the levigation, which consists principally
of carbonate of lead and a small quantity of oxide of lead and minium,
may, by being slightly calcined in a close vessel somewhat below red heat,
be rendered fit for acting again upon the salt. It may therefore be made

page_text: use of in a succeeding operation, or it may be used in the same way as
litharge for the manufacture of acetate of lead, chromate of lead (chrome
yellow), and for various other purposes. When making carbonate of lead
which is intended to be calcined, the presence of sulphates in solution must be
carefully avoided, as it is evident that sulphate of lead would be formed, which
would accumulate at each operation, and, diminishing the quantity of the
oxide of lead, would occasion considerable waste; but in manufacturing
ceruse the inconvenience would not be so great, as it would only occasion the
existence of slight traces of sulphate of lead. Water containing bicarbonate
of lime may be advantageously employed, in consequence of the carbonic acid
which it produces on.reaction. In manufacturing ceruse it will be advisable
to employ litharge containing as little copper as possible, but this is of no con-
sequence when the carbonate of lead is intended for calcination. It will thus
be understood, that when oxichloride of lead (produced by the action of oxide
of lead on sea salt) is subjected to the action of carbonic acid at an ordinary
temperature, and afterwards at the boiling point to the action of carbonate of
lime, carbonate of lead is obtained in a fit state to be used as white lead,
provided the carbonate of lime employed be sufficiently pure; or the carbonate
of lead, if calcined, may be employed over again, in the state of oxide, for
decomposing fresh portions of sea salt; and also, that on submitting a mixture
of soda and oxichloride of lead (obtained by the reaction of oxide of lead upon
sea salt) to the action of carbonic acid, carbonate of lead is obtained in a
proper state to be used as white lead, and the sea salt may be again employed
in fresh operations.
: Having now described my Improvements in the Manufacture of Carbonate
of Lead, I desire it to be understood, that although I have described certain
apparatus for carrying my improvements into practical operation, I do not
intend to claim the use of such apparatus, the details of which have been
particularly pointed out in order that my mode of operation may be well
understood. But that which I claim under the above in part recited Letters
Patent is,
First, the decomposition of oxichloride of lead by means of carbonic acid,
either in a gaseous state or dissolved in water.
And, with respect to the second head of my Invention, I claim the
treatment of the materials at the boiling point, which greatly facilitates the
chemical action.
In witness whereof, I, the said Jean Marie Fourmentin, have hereunto
set my hand and seal, this Twentieth day of November, in the year
of our Lord One thousand eight hundred and forty-seven.
(L.s.) FOURMENTIN JEANE.

page_text: AND BE IT REMEMBERED, that on the same Twentieth day of Novem-
ber, in the year above mentioned, the aforesaid Jean Marie Fourmentin came
before our Lady the Queen in Her Chancery, and acknowledged the Speci-
fication aforesaid, and all and every thing therein contained, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute in that case made and provided.