Improvements in the Manufacture of White Lead.
Year: 1896

page_text: Date of Application, 7th July, 1896-Accepted, 17th Oct., 1896
COMPLETE SPECIFICATION.
Improvements in the Manufacture of White Lead.
I, ARTHUR BENJAMIN BROWNE, of 119 Water Street, Boston, Massachusetts,
United States of America, Chemist, 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:-
The object of my invention is to produce white lead for use as pigment for paint
and by means of the continuous electrolytic process herein specified and claimed.
The electrolyte employed is a neutral solution of an acid with an alkaline base,
preferably such as nitrate of soda, but an acetate of soda may be employed or any
other available solution which gives the proper reactions and which when electrolyzed,
will separate into an acid at the anode and an alkali at the cathode of the electrolyzer,
but my process has particular relation to the use of nitrate of soda and it consists,-first,
in introducing the nitrato of soda into an electrolyzing tank or tanks, in which
an anode or anodes and a cathode or cathodes are placed, electrically connected to
an efficient source of electrical energy. The anode being preferably a pig of lead,
and the cathode being preferably of copper, or its equivalent. The solution under
electrolysis separates. The nitric acid goes to the lead anode and attacks it, forming
nitrate of lead. The caustic soda goes to the cathode forming alkaline hydrate.
Second: In drawing off the nitrate of lead through one pipe and the alkaline
hydrate through another into separate tanks.
Third: In mixing the two solutions by proper apparatus in a common receiver,
where the nitric and caustic or alkaline hydrate unite, reforming neutral nitrate of
soda, and precipitating the lead as a lead hydrate.
Fourth: Separating the hydrate of lead precipitate from the nitrate of soda by
filtering it, then carbonating the precipitate while in the state of hydrate to form basic
amorphous carbonate of lead and then drying it for use, also returning the neutral
nitrate of soda to the receptacle from which it was first taken, and in condition to be
used again in the same manner.
l'umps, pipes and the other necessary appliances for carrying on the above process
are of course employed.
In practicing the above process certain difficulties are encountered such as properly
dividing the electrolyzer tanks, to ensure the proper reactions, without local uctions;
preventing the formation of sub-salts of lead, etc.
Unless the electrolyzer is properly constructed and arranged the local action will
cause the acid and alkali to recommingle more or less as the case may be, thus
rendering the solution more or less alkaline, and lead hydrate is deposited in the
electrolyzer hindering the proper action of the process. In order to more perfectly
practice my process and to overcome these difficulties and irregularities in my process
I have invented the apparatus herein specified and shown, which consists of a
tank (A) for containing nitrate of soda (in the present instance) a pipe (a) leading
therefrom to a pipe (a), pipe or pipes (1) leading into central compartment or
compartments (d*) secured in electrolyzer or electrolyzers (B) and preferably leading
to the bottom thereof, discharge pipe or pipes (4) leading from the centre compartment
or compartments (dx) of the electrolyzer or electrolyzers (B) and into a pipe (6)
which leads to a tank (D) to convey sodium hydrate to tank (D), discharge pipe or
pipes (3) leading from the anode side or sides X of the electrolyzer or electrolyzers (B)
to convey lead nitrate to and through pipe (61) to tank (C), pipes (c) and (d)

page_text: connecting from tanks (C) and (D) respectively to and through pipe (e) to tank (E)
where the two solutions are mixed and lead hydrate is precipitated by the union
of the nitrate and sodium hydrate solutions. Pump (G) draws the lead hydrate
precipitate and nitrate of soda from tank (E) and discharges it into filter press (F),
where the nitrate of soda is discharged into pan (F) and by pump (H) forced up
into tank (A) through pipe (h) for use again, thus completing the circuit and process
of forming lead hydrate, which as a filtrate is left in press (F) to be carbonated to
a basic amorphous carbonate of lead or what is called in the arts white lead pigment
free from crystals and blue lead which occur in all other processes. The electrolyzers (B)
are formed as shown. The central compartments are constructed by securing foraminous
material to suitable framing which extends across the tanks from side to side, so that
the solution is able to percolate through the foraminous sides thereof, anodes (a*) are
sustained in chambers (a) of the electrolyzers (B) and are preferably an ordinary pig
of lead. They are preferably electrically connected to the positive wire (k) of a
source of electrical energy (K). Cathodes (ex) are sustained in chambers (y) of the
electrolyzers (B) and are preferably of copper or its equivalent electrically connected
with the negative wire () of the source of electrical energy (K), thus when the
nitrate of soda solution is admitted into the central chamber (dx) of the electrolyzers (B),
the solution will percolate into chambers (c) and (y) to the proper point or level, and
when the electrical energy is caused to flow or act, the nitrate of soda separates
and nitric acid goes to the (2) chamber and to the anode and as a solvent of lead
attacks the lead and oxidizes it, while the caustic soda or hydrate of sodium goes
to the cathode (C) in chamber (y). From local causes in ordinary practice the
alkaline solution percolates into the acid compartments (r) and tends to throw down
the nitrate of lead in solution therein. To prevent this action I create over-balancing
pressure on the electrolyte in the central chambers (d) by raising the level of the
liquid therein or I cause an increase flow therefrom through the discharge pipe (4) of
such rapidity that the density of the electrolyte in said central chamber is kept below
the point where percolation through the foraminous diaphragm and into the anode
compartment would ensue, or I may use a combination of pressure and increased
flow as hereinbefore described; in other words I prevent alkalinity in the anode
compartment (x) by regulating the character of the fluid in the central chamber in
any way which will accomplish the desired end, whether by increasing the pressure
therein, or by increasing the flow therefrom, or by both together or by the character
of the foraminous wall thereof.
I prevent the formation of sub-salts of lead in the anode compartment by either
the addition of a free acid thereto as required or by reducing and maintaining the
density of the nitrate solution below the point at which such salts form. This I do
in a convenient manner; as for instance by drawing off the nitrate of lead in
solution from chamber (a) through pipe (3) which leads to pipe (61) and to nitrate
tank (C), and supplying the anode chamber with fresh electrolyte through pipe (2).
I also temper the alkaline hydrate in compartment (y) by drawing off the said
hydrate through pipe (5) and into pipe (6) and thence to tank (D). This operation
serves two desirable purposes, to temper the alkalinity in chamber (y) and to furnish
proper amount of alkali for precipitating the hydrate of lead from the nitrate of lead
in tank (E). All of the connecting and operating pipes are of course furnished with
proper valves with which to regulate the flow of liquids through them. The operation
of my invention by means of the apparatus specified and shown herein will be readily
understood from the above description without further explanation. I have shown
all electrolyzers arranged on a common level, the electrical current passing from one
to the other, but these conditions may be changed in many ways, without changing
my invention and process which produces hydrated oxide of lead continuously previous
to the act of carbonating. The carbonating may be accomplished in many ways after
the lead hydrate has been separately formed without causing crystals of lead and blue
lead. My product being amorphous basic carbonate of lead after the carbonating
process has been performed, it is an impalpable substance and perfectly homogeneous
in its structure.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. In an electrolytic process for the production of white lead, the within described
process of producing hydrate of lead which consists in electrically separating a
solution of a salt of an alkaline base into anion and cathion, maintaining separation
of said anion and cathion, causing said anion to dissolve metallic lead, to form a
solution of a soluble salt of lead; and finally mixing the same with the said cathion
to precipitate hydrate of lead and separating said lead hydrate from the solution,
substantially as specified.
2. In an electrolytic process for the production of white lead, the within described
process of producing hydrate of lead, which consists in electrolytically separating
a solution of a salt of an alkaline base into anion and cathion, maintaining separation
of said anion and cathion, causing said anion to dissolve metallic lead to form a
solution of a soluble salt of lead, and finally mixing the same with the said cathion
to precipitate hydrate of lead and separating said lead hydrate from the solution
and returning said solution to the electrolyzers, substantially as specified.
3. In an electrolytic process for the production of white lead, the within described
process of producing hydrate of lead, which consists in electrolytically separating a
solution of a salt of an alkaline base into anion and cathion maintaining separation
of said anion and cathion, causing said anion to dissolve metallic lead to form a
solution of a soluble salt of lead, and finally mixing the same with the said cathion
to precipitate hydrate of lead and separating said lead hydrate from the solution
and then carbonating said lead hydrate to form white lead pigment, and returning
said solution to the electrolyzers, substantially as specified.
4. In an electrolytic process for the production of white lead the within described
method of maintaining a separation of anion and cathion by a preponderance of
pressure in the electrolyte in the central chamber of an electrolyzer, substantially as
specified.
5. In an electrolytic process for the production of white lead, the method of
maintaining separation of anion and cathion by causing a flow of the electrolyte
through the central chamber of the electrolyzer, substantially as specified.
6. In an electrolytic process for producing white lead, the herein described method
of preventing objectionable formation of sub-salts of lead, etc., by adding an oxidizing
agent to the electrolyte, substantially as specified.
7. In an electrolytic process for producing white lead the herein described method
of preventing the formation of objectionable sub-salts of lead, by regulating the
density of the solution, substantially as specified.
Dated this 7th day of July 1896.
ALLISON BROS.,
Agents for the Applicant.