Improved Process of Producing Basic Lead Carbonate and Obtaining Certain Bye-products.
Year: 1896

page_text: Date of Application; 26th Mir.; 1896
Complete Specification Lelt, 22nd Dec.,. 1896-Accepted, 13th Feb... 1897
FIOVISIONAL SPECIFICATION..
Improved Process of Producing Basic Lead Carbonate and
Obtaining Certain Bye-products.
We, THE CHEMICAL AND ELECTROLYTIC SYNDICATE LIMITED, OSCAR JULIAN
STRINHART Ph.D., and JULIUS LEONARD Fox VOGEL, Chemist, all of 6, Clement's
Lane, Lombard Street, in the City of London, do hereby declare the nature of this
invention to be as follows:-
This invention relates to an improved. process of conjointly producing basic lead
carbonate and certain bye-products by a continuous cycle of operations wherein lead
nitrate is formed and, is, then, decomposed by, sodium carbonate for, the production of
basic lead carbonate, the sodium nitrate. which is also produced, by the.decomposition.
being then decomposed to regenerate nitric acid, for the production of, more lead
nitrate from a fresh. batch of lead oxide while the alkali is recovered. chiefly, as, caustic
soda and partly as sodic carbonate it, being, understood, that where sodium carbonate
and caustic soda are referred to potassium carbonate and potash are included.
The special object of the present improved process is to obtain carbonate of lead
as. pure as possible and free from basic nitrate whose presence would render the lead.
carbonate unfit for use as a pigment or for any other commercial purpose..
We proceed as follows:-Crude. pig lead is oxidized and the oxide of lead thus.
obtained is dissolved in nitric acid to form lead nitrate. Any, silver, copper, and,
other metallic impurities that may have been present in the crude, lead are now.
eliminated. from the lead nitrate by the addition of finely divided: metallic lead
whereby the silver and some other metallic impurities. are precipitated along with the
finely divided lead forming ultimately rich silver lead as a bye-product of the
process. This purification of the lead nitrate is however only required if crude pig,
lead has been used and by this means the cost of refining the lead, is saved at the
same time that a valuable bye-product is obtained; but it is of course to be understood
that although for economical reasons crude lead; would be used the process is not
limited in this respect as it will be obvious that oxide made from refined lead might
be used although with less advantage..
The solution of pure lead nitrate produced as above described is added to a solution.
of sodium carbonate the carbonate being in excess of the theoretical equivalent
required to form normal carbonate of lead, the purpose of this excess being to prevent
the formation of basic nitrate of lead 'and to give. the requisite basicity to the
carbonate of lead.
The best mode of proceeding is to heat liquors of about the strength of cold
saturated solutions of the lead nitrate and sodium carbonate in the proportions above
mentioned nearly to boiling point and then to run the lead solution into the alkali.
solution keeping the mixture thoroughly. agitated meanwhile and whilst continuing
to boil it for a sufficient time. to ensure complete decomposition whereby basic
carbonate of lead is precipitated leaving in solution nitrate of soda and undecomposed
carbonate of soda.corresponding to the excess employed! This solution of nitrate of
soda and carbonate of soda after being soparated from the precipitate is then to be
boiled down; the carbonate of soda- being separated by crystallization or not. If
separated the carbonate is used over again and the nitrate is mixed and ground with
such a quantity of ferric oxide as will prevent the fusing or fluxing of the sodic

page_text: nitrate when heated in the operation next described. If the carbonate is not separated
it is ground along with the nitrate and ferric oxide, the whole of the soda (or nearly
so) both of the nitrate and carbonate being recovered as caustic soda after furnacing.
The pulverulent mixture is then furnaced in an inclined revolving retort in the
nanner described in the Specification of Letters Patent dated the 9th day of
April 1895 No. 7273; whereby are obtained as final products nitric acid for making
a fresh batch of lead nitrate and caustic soda.
Dated this 26th day of March 1896.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
Improved Process of Producing Basic Lead Carbonate and
Obtaining Certain Bye-products.
We, THE CHEMICAL AND ELECTROLYTIC SYNDICATE LIMITED, OSCAR JULIAN
STRINHART, Ph.D. and JULIUS LEONARD Fox VOGEL, Chemist, all of 6, Clement's
Lane, Lombard Street, in the City of London, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
This invention relates to an improved process of conjointly producing basic lead
carbonate and certain bye products by a continuous cycle of operations wherein
lead nitrate is formed and is then decomposed by sodium carbonate for the production
of basic lead carbonate, the sodium nitrate which is also produced by the decom-
position being decomposed into nitric acid and caustic alkali by a separate operation
in order to regenerate nitric acid for the production of more lead nitrate from a
fresh batch of lead oxide while the alkali is ultimately recovered as caustic soda or
chiefly as caustic soda and partly as sodic carbonate. It is to be understood that
wherever sodium carbonate and caustic soda are referred to, potassium carbonate and
caustic potash are included.
The special object of the present improved process is to obtain carbonate of lead
as pure as possible and free from basic lead nitrate whose presence would render the
lead carbonate unfit for use as a pigment or for any other commercial purpose.
We proceed as follows:-Crude pig lead is oxidized and the lead oxide thus
obtained is dissolved in nitric acid to form lead nitrate. Any silver, copper, and
other metallic impurities that may have been present in the crude lead are now
eliminated from the lead nitrate by the addition of finely divided metallic lead
whereby the silver and some other metallic impurities are precipitated along with
the excess of finely divided lead, the precipitate forming ultimately rich silver lead as
a bye product of the process. This purification of the lead nitrate is however only
required if crude pig lead has been used to form the lead oxide and in that case the
cost of refining the lead is saved at the same time that a valuable bye-product is
obtained but it is of course to be understood that although for economical reasons
crude lead would generally be used the process is not limited in this respect as it
will be obvious that oxide made from refined lead might be used although with less
advantage.
The solution of pure lead nitrate produced as above described is added to a solution
of sodium carbonate the carbonate being in excess of the theoretical equivalent
required to form normal carbonate of lead, the purpose of this excess being to prevent
the formation of basic nitrate of lead and to give the requisite basicity to the
carbonate of lead.
The best mode of proceeding is to take solutions of lead nitrate and of sodium

page_text: carbonate (each being of about the strength of a cold saturated solution) in the
proportional quantities above mentioned so that the carbonate will be in excess, and
to heat them nearly to boiling point and then to run the lead solution into the
alkali solution keeping the mixture thoroughly agitated me inwhile and whilst
continuing to boil it for a sufficient time to ensure complete decomposition whereby
basic carbonate of lead is precipitatad leaving in solution nitrate of soda and
undecomposed carbonate of soda corresponding to the excess employed. This solution
of nitrate of soda and carbonate of soda after being separated from the precipitate by
decantation or filtration (or hy both means) and subsequent washing, is then to be
boiled down to dryness, the carbonate of soda either being separated by crystallization
or left in admixture with the nitrate. If the carbonate is separated it may be used
over again with more lead nitrate solution as before described, but if the carbonate
is not separated the whole of the soda (or nearly so) both of the nitrate and carbonate
will be recovered as caustic soda after the furnacing operation next described.
The sodic nitrate from which the carbonate has been separated or the mixture of
sodic nitrate and solic carbonate is then to be ground with such a quantity of
ferric oxide as will prevent the fusing or fluxing of the sodic nitrate when heated
to a high temperature.
The pulverulent mixture of sodic salt or salts and ferric oxide is then furnaced in
an inclined revolving retort in the manner described in the Specification of Letters
Patent dated the 9th day of April 1895 No. 7273; whereby are obtained as final
products nitric acid for making a fresh batch of lead nitrate and caustic soda.
We are aware that it has been proposed to produce basic carbonate of lead by a
process which (apart from the mode of performing the furnacing operation) differs
from the foregoing mainly in the fact that caustic soda was added along with
carbonate of soda for imparting basicity to the lead carbonate obtained by
precipitation from a solution of lead nitrate, but we have found that the presence
of caustic soda at this stage is prejudicial to the operation and that the desired result
can only be obtained by using carbonate of soda alone and in excess as above
described so as to prevent the formation of basic nitrate of lead and impart the
desired basicity to the carbonate of lead.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
The herein described process of producing basic lead carbonate and also caustic
alkali and nitric acid as bye-products which process consists essentially in
decomposing lead nitrate with sodium carbonate in excess to precipitate basic lead
carbonate as specified.
D
0011
°
D
1000
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.