Especially Carbonate or Oxycarbonate of Lead (White Lead).
Year: 1886

page_text: Date of Application, 8th Feb., 1886.
Complete Left, 8th Nov., 1886.
Complete Accepted, 8th Feb., 1887.
Especially Carbonate or Oxycarbonate of Lead (White Lead).
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of this Invention to be as follows:-
This Invention has for its object a new and improved process, or method, of
manufacturing all salts of lead generally, and more especially the carbonate and
oxycarbonate of lead, (commonly known as white lead,) and consists in employing,
for this purpose, oxides of nitrogen, which may be regenerated, if desired.
The Invention is based on the fact that lead and oxide of lead are dissolved, in large
quantities, in any solution formed of water, lead, nitrogen, and oxygen.
The chief solutions of this kind are ;-
1° Solutions of nitrate of lead: (no³) Ph.
2° Solutions of hyponitrate of lead: 20 (Pb0)² + HO.
3° Solutions of nitrate of lead: no Pb + H2O.
1227
4°-Solutions of nitrosonitrate of lead (13) Pb + H2O.
5° Solutions of dinitrosonitrate of lead, containing two atoms of lead
123
}}
Pb PbO + H2 O.
6° Solutions of dinitrosonitrate of lead containing a variable atomic proportion
of lead:
3Pb (PbO) + (H2O)"
РЬ
7° Solutions obtained by mixing two, or a larger number, of the above mentioned
solutions.
If lead is added to any of the above mentioned nitro-plumbic solutions, the atomic
composition of the solution is altered, and hydroxides are formed which are dissolved,
or precipitated, according to the degree of lieat, and concentration of the solution.
[Price 8d.]

page_text: C.) (no°)* Pb + 2 PbO + Ph = (no)² + 4 PbO.
#
The deutoxide of nitrogen may be converted into hyponitric acid, by any suitable
means, for instance, by its being simply brought into contact with air. When
hyponitric acid, either in the liquid, or gaseous state, is brought into contact with a
basic material, such as hydroxide of lead, hyponitrate of lead is again formed and this
salt may be utilized, as above stated. By adding to the solution a certain proportion
of lead, which is dissolved also as above described, hydroxides of lead are again pro-
duced in which the oxygen of the metallic oxide is provided for by the hyponitric
acid. The deoxydization of the hyponitric acid again produces deutoxide of nitrogen
which by absorbing oxygen (for instance from air) may be reconverted into hyponitric
acid. This acid, by the above described reactions and transformations, can indefinitely
produce hydroxides of lead, the oxygen of which is indirectly taken from the air, or
any other convenient source of oxygen.
In the above formula, the atomic proportion of water H2O, has not been taken into
consideration, consequently these formula may be more exactly written as follows;-
A.) (NO3)2 Ph + Pb + (H² O)" : Pb PыO H2O + (HO)ª-'.
NO³
=
no2
103
}}
11-2
B.) NO PL PыO H² O + (H² 0)ª−1 = (No²) 2 Pb (PbO H² O) 2 + (H² 0)*~².
C.) (NO) Pb (PыO H² O)² + (H² O) + Pb = (no²)² (PbO H²‍0)ª+ (H²0)ª – 3.
(When deutoxide of nitrogen is liberated, or evolved in the gaseous state, the oxide
of lead with which it was in combination becomes hydrated) The conversion of
deutoxide of nitrogen into hyponitric acid may be explained by the following

page_text: notation no + 0 = no‘. The hyponitric acid so obramed may be condensed m the
solution containing an excess of hydroxide lead and generates hyponitrate of lead.
This latter salt can indefinitely reproduce the above described reactions. However,
the hyponitric acid may also be collected and used afterwards in the above process,
or it may be employed for any other suitable use. In short, by employing a nitro-
plumbic solution as a vehicle, it is possible, by this process, to convert lead into
hydroxides of lead, the necessary oxygen for the oxidation of the lead being taken
from the air, and the water for its hydration being furnished by the water of the
solution itself. The hydroxide of lead is obtained in a finely-powdered condition. It
may be converted, by heat, into anhydrous oxide of lead (litharge or massicot) and
consequently into red lead. This hydroxide may also be employed for the manufacture
of carbonate or oxycarbonate of lead (white lead) as its affinity for carbonic acid is
very high. The treatment of the hydroxide, by carbonic acid may be effected in the
solution of nitro-plumbic salts in which the hydroxide of lead is generated. For this
purpose, a current of carbonic acid is caused to pass through the solution; the carbonic
acid employed may be either pure carbonic acid or carbonic acid mixed with other
gases, for instance such as the products of combustion in any furnace or the escaping
gases from a lime-kim etc, etc. The carbonic acid may also he obtained from any
convenient source, such as bicarbonate of soda, etc, etc. According to the degree of
carbonation, carbonate, or oxycarbonate of lead is obtained. The hydroxides of lead
obtained by the method and operations above specified are also applicable to the
manufacture of other salts of lead, such as acetates, sulphates, oxalates, chloride,
The more
bromide, and nitrates of lead, plumbites, plumbates, double-salts, etc, etc.
or less complete saturation of the hydroxide of lead by any acid may also be effected
in proportion, and as quickly, as this hydroxide is produced to this end it is sufficient
to cause the acid employed for the saturation of the base, to enter the solution during
the formation of the hydroxide. For instance, carbonate, or oxycarbonate of lead
(white lead) may be obtained by the passage of a current of carbonic acid gas through
the solution. But this saturation may, if desired, be effected afterwards, and in a
separate apparatus.
I will now describe how the method or process based upon the above principle is.
preferably to be put in practice:--Any suitable vessel is filled to about two-thirds of
its capacity, with a solution of nitro-plumbie salts, and a certain proportion of lead is
added to the solution, which may be heated by any convenient means. The lead is
dissolved by the solution as hydroxide of lead; it is oxidized by the oxygen of the
oxide of nitrogen contained in the nitro-plumbie salts in the solution. The oxide of
nitrogen, deprived, by this reaction, of part of its oxygen is wholly or partially
converted (according to the original proportion of oxygen it contains) into deutoxide
of nitrogen, which evolves, or is regenerated in the solution as will be hereafter
explained. During this operation a current of gas furnished by the combustion of
fuel in any furnace (for instance in the furnace employed for heating the solution)
is forced through the solution by any convenient means, such as a pump of any kind.
According to their composition, the gases, or products of combustion, are employed
directly from the furnace, or they are washed before entering the solution. These
products of combustion are chiefly composed of:-carbonic acid, nitrogen, oxygen, etc;
their action is first to furnish the necessary carbonic acid to transform and precipitate
the hydroxide of lead in the form of carbonate, or oxycarbonate of lead (white lead)
and secondly to furnish the proportion of oxygen necessary for the transformation, in
the solution itself, of the greater part of the deutoxide of nitrogen generated, into
hyponitric acid. This hyponitric acid in its turn combines with part of the hydroxide
of lead and again produces hyponitrate of lead capable of dissolving a fresh amount of
lead by this means, the solution is restored to its original condition. When the
products of combustion are forced into the solution at a suitable temperature they
may be used for imparting to the solution the proper degree of heat. On their egress
from the first, vessel containing the solution, the products of combustion are caused
to pass through condensers filled with nitro plumbic solutions which retain any small
proportion of nitrous products occasionally brought over by the gases. When the

page_text: solution in the condensers is supposed to contain a practically higher proportion of
oxide of nitrogen than at the beginning of the operation, it is caused to flow into the
first vessel and replaced by solution taken from this vessel. This change in the
position of the nitro-plumbic solutions is effected as often as is necessary. Before
they finally escape, the products of combustion pass through washing vessels con-
taining ferrous sulphate (having a high degree of acidity) or any other like substance,
by which the last traces of nitrous products are absorbed or retained, and may be,
subsequently, set free when submitted to certain conditions. These oxides of nitrogen
may thus be collected for the purpose of being re-introduced into the nitro-plumbie
solutions. The white lead generated as above is removed from time to time, and
replaced by lead as often as is judged necessary. By this means, the operation is
rendered continuous. If necessary, the products are washed, and they are used in the
ordinary way.
The above described process may also be put in practice as follows:-Instead of
dipping into the solution, the lead is placed in a vessel, in a conveniently divided
condition, and the solution of nitro plumbic salts is poured upon it in the form of
spray, either continuously, or at suitable intervals; in this manner the lead is
dissolved in the solution. As above stated the solution of the lead is rendered more
rapid by the proper degree of saturation, pressure, and heat. A current of carbonic
acid is employed to transform the hydroxide of lead into white lead. The regeneration
of the oxides of nitrogen in the nitro-plumbic solutions is effected also as in the first
above described process.
In all the above mentioned processes lead may be replaced by oxide of lead (litharge
or massicot) The operation is conducted as when lead is used, but it is no longer
necessary to effect the regeneration of the oxides of nitrogen of the nitro-plumbic
solution, because these compounds are not decomposed as they do not furnish any
oxygen for the oxidation of lead. However, as in some special cases, the hyponitric
acid produces nitrates (by combining with oxide of lead) and evolves deutoxide of
nitrogen, air may be forced into the solution, in order to prevent the latter gas
escaping, and to convert it into hyponitric acid As the solution contains a large
proportion of base in excess, this hyponitric acid immediately produces hyponitrates
of lead acting in the above described way.
The manufacture of lead salts according to this Invention may be carried on either
in apparatus already employed in chemical industry, or in apparatus especially con-
structed for this purpose. It will be understood that the nature of the Invention
would not be varied by modifications of detail, so long as its essential features remain
unchanged. For instance, in special cases, may add to the solution of nitro-plumbie
salts, any other suitable substances having any influence either upon the rapidity of
the manufacture, or upon the quality of the products obtained.
A. M. CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: Especially Carbonate or Oxycarbonate of Lead (White Lead).
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of this Invention (a communication to me from
abroad by Oscar Eyckens (Manufacturer) of 237 Faubourg St. Honoré, Paris,
France) 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 manufacturing salts of lead
generally and more especially the carbonate and oxycarbonate of lead commonly known
as white lead.
The invention is based on the employment or application of nitroplumbic solutions
and especially of nitrate of lead.
The initial stage of the process in which nitrates of lead are employed is only
performed once and rapidly produces polybasic nitrites of lead by the addition of
metallic lead to the solution of nitrate of lead. From this point the several plases
and the general ensemble of the process are based on the following chemical
reactions:
(1) On the property possessed by solutions of nitrate of lead of converting lead
into hydrate, the oxygen necessary for the formation of the hydrate of lead being
taken from the nitrous acid which combined with oxide of lead, constitutes nitrite of
lead.
(3) On the property possessed by nitrogen dioxide of becoming converted by its
contact with the oxygen of the air into a double acid formed by the combination of
nitric acid and nitrous acid and consequently denominated hypo-nitric acid.
2 (NO3) + 40 ...... = NO + N2 08
(4) On the property possessed by nitric and nitrous acids of forming nitrates and
nitrites of lead with oxide or hydrate of lead.

page_text: with lead, into nitrite of lead possessing all the properties enumerated in clause 1.
Nitrates of lead in solution when brought into contact with lead become converted
into basic nitrites of lead, by giving up a portion of their oxygen to the lead to form
basic nitrite of lead.
Pb Nº 0 + 2 Pb = Pb Nº 0' + 2 PbO
Pb N 0 + Ph N2 O + 2 Pb = 2 Pb Nº 01 + 2 Pho
(6) On the property possessed by solutions of nitrite of lead of being less and less
soluble in proportion as they contain a larger co-efficient of base, of which a portion
may even be precipitated in the form of lead hydrate, when this base is in excess.
4 (PbQ) N² 0³ + H2O = 3 (PыO) N² (³ + Pb H² (²
(7) On the property possessed by carbonic acid of returning solutions of polybasic
nitrite of lead to a neutral condition, by precipitating the excess of base in the form of
carbonate of lead which mixed with the hydrate of lead which precipitates at same
time when this base is in excess, forms the product usually termed white lead.
4 (PLO) N2 03 + 2 H2O + 2 00° == Pb N2 O + H2O + 2 Pb CO³ + Pb H² 0²
In all these reactions the oxides of lead are hydrated. The nitric or nitrous
clements are not always in the proportion: 1:1 which, however, does not modify
them in any way.
The successive reactions which can be repeated indefinitely are shortly as follows:-
Deoxidation of the nitrous acid of the nitrite of lead, during the contact of a hot
solution of this salt with the lead and the consequent oxidation of the lead and
disengagement of nitrogen dioxide. Conversion of the nitrogen dioxide by means of
oxygen into a double acid formed by the combination of nitric acid and nitrous acid.
Formation anew of nitrite of lead by the contact first of nitric acid, and secondly
of nitrous acid, with the lead or oxide of lead. Lastly, production of white lead by
the combination of carbonic acid with the excess of base in the solutions of polybasic
nitrites of lead.
Upon the several properties hereinbefore enumerated is based as above mentioned,
a process of manufacture, whereby with a relatively small quantity of nitrite of lead
which is constantly regenerated, an indefinite quantity of lead is converted into white
lead, it being merely necessary to compensate for the slight loss of solution of nitrite
of lead, which occurs during the treatment.
In addition to this regeneration of the vehicle which constitutes one of the important.
features of the invention, it has also been sought to find a means which would allow
of attacking and oxidising the lead and of hydrating the molecules and at same time
of carbonating them before they have had time to become diluted, or dissolved as in
the chemical processes heretofore employed, whereas in the Dutch process and in
others in which vapours are employed, which require a considerable time for their
reaction, the transformed molecule remains compact upon the lead, which is one of the
principal elements for the obtainment of a product of the required density and covering
power. In order to arrive at an equivalent result, the lead is immersed in a solution
of nitrite of lead, through which is passed a continuous stream of carbonic acid which
is finely divided and brought into uninterrupted contact with the lead. In this
manner the molecule attacked becomes carbonated at the moment of its formation and
therefore before it has had time to become divided or diluted.
During these reactions, the nitrite of lead is decomposed, as it is the nitrous acid of
the nitrite of lead which furnishes the oxygen necessary for the oxidation of the lead,
and which is thus converted into gaseous nitrogen dioxide which is disengaged. The
solution would in this manner become inert and be rendered useless were not a means
provided of regenerating it, so as to enable it to be used indefinitely. Being a very
costly element, without regeneration, the process would fail of commercial success.
In order to take advantage, to this end of the properties enumerated in clauses
Nos. 3, 4 and 5 of the present specification I add to the carbonic acid introduced into

page_text: the solution, such a sufficient quantity of air that the gaseous nitrogen dioxide at the
moment of its formation, will by contact with said air be converted into hypo-nitric
acid which by contact with the hydrate of lead is transformed into nitrite and nitrate
of lead and finally the latter in contact with the lead becomes reconverted into a
polybasic nitrite of lead, the entire operation being effected in the midst of the initial
solution itself and in a continuous manner the reactions constituting an uninterrupted
cycle of operations. During this time the white lead formed upon the lead being
contained in a solution which is highly agitated by the introduction of the gases
naturally becomes disintegrated and owing to its density falls to the bottom of the
apparatus, whence it is withdrawn and passed through a filter press, by which means
is obtained on the one hand a solid product consisting of white lead and on the other
hand, a solution of polybasic nitrite of lead. In order to avoid the loss of the nitrous
gases which might be carried away by the rapid passage of the gases through the
apparatus, they are caused to pass through a series of towers containing the solution
of polybasic nitrite of lead coming from the filter, which solution intercepts the last
traces of the nitrous gas and is returned to the first apparatus with all its original
strength. The white lead removed from the filter press can after being washed, be
either dried or ground with oil by the ordinary means.
In order that the process of manufacture may be more readily understood I have
illustrated in the accompanying drawing, one arrangement of apparatus which may be
employed for the purpose.
The lead after being reduced to shavings is placed in a chamber A termed a
converter inasmuch as in it the lead is converted into white lead.
At the bottom of the chamber is a pipe a for the supply of the gases which are
introduced through distributors so constructed as to prevent the white lead from
clogging the orifices. Above this is a grating upon which the lead is placed through
an opening dat top provided with a cover. e is the inlet pipe for the liquids, and fan
outlet pipe for the gases. g is a cock at which the white lead is drawn off as fast as
it is produced.
When the apparatus is about two thirds filled with lead and a solution of nitrite of
lead I inject therein by means of an air compressor, gases of combustion with which
have been mixed the necessary quantity of air to ensure the reactions being properly
and quickly performed. The gases which should be previously heated to a suitablo
temperature are after passing through the converter conducted to a series of towers B
where they are deprived of all traces of the nitrous acid which they may carry with
them.
The gases entering at bottom of the tower first pass through a distributor band
leave the tower at top by a pipe, which conducts them into another similar tower and
so on, and ultimately escape into the atmosphere.
These towers contain no lead, but simply solutions of polybasic nitrite of lead,
which are introduced by pipe d from the bottom of the converter where the more
basic solutions of nitrite of lead have descended together with the white lead. By
opening cock at the bottom of the converter direct communication is established
between it and the monte-jus or force pump C, by which the product is transferred
to the filter press E which retains the white lead, while the solution flows into another
force pump
D whence it is returned to the towers. The solution being at this moment
a polybasic nitrate has a great affinity for nitrous acids and consequently absorbs the
nitrous gases which may
have been carried out of the converter.
Thus by means of the force pump, the liquids are frequently transferred between
the converter and the towers.
The white lead on leaving the filter press needs only to be properly washed, the
washing water being afterwards concentrated and returned to the apparatus, adding
thereto at long intervals, a little nitrate or nitrite of lead to replace any loss which
may have been incurred in the working.
One washing only of the white lead is required to bring it to a merchantable
condition and it needs only to be dried or ground in oil by the ordinary means.

page_text: Instead of employing lead in the above process, litharge or massicot may be
substituted.
The process may be carried on in any suitable apparatus or by any other means
without in any way affecting the nature of the invention, so long as the essential
conditions of the process are retained.
Having now particularly described and ascertained the nature of the said invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1st. The hereindescribed continuous process of manufacture of white lead on a
commercial scale, by means of lead, which consists in employing as a vehicle, solu-
tions of nitrite of lead, which are constantly regenerated by oxygen as hereinbefore
described.
2nd. The apparatus for the manufacture of white lead arranged and operating
substantially as herein described and shewn in the drawing.
A. MELVILLE CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.