Process of Manufacturing White Lead by Electrolysis.
Year: 1897

page_text: Date of Application, 19th Aug., 1897-Accepted, 11th Dec., 1897
COMPLETE SPECIFICATION.
Process of Manufacturing White Lead by Electrolysis.
I, HERMAN CHARLES WOLTERECK, of 25, Whitehall Street, City County and State
of New York, United States of America, Consulting Chemist, do hereby declare
the nature of this invention and in what mauner the same is to be performed to
be particularly described and ascertained in and by the following statement:-
This invention relates to a process of manufacturing white lead by means of
electrolysis, by which means white lead can be produced more perfectly and
economically than has hitherto been possible and without endangering the health
of the operators as has heretofore been the case with other processes.
The process consists in first producing a soluble salt of lead, or such a salt of lead
as will be transformed into the hydrated carbonate of lead by the reactions taken
place in this process, all such salts of lead being termed "soluble salts of lead" in the
sense of this invention, in the presence of Carbonic acid gas and caustic alkali, by
which process the hydrated carbonate of lead is formed in one reaction and yields a
product of exceptional fineness.
For the purpose of my process I use an electrolyte composed of a solution of a
mixture of salt of an alkali in combination with any acid which will form soluble lead
salts in the sense of this invention and the bi-carbonate of any alkali, which will
furnish the carbonic acid as required by the reaction. The percentage of the
electrolyte solution may vary greatly according to the salts employed. The salts of
Acetic, Nitric, Sulphuric, Hydrochloric and various other acids in combination with
an alkali may be employed advantageously in this process. Care should be taken to
keep the temperature of the electrolyte below 25° Cels. as the resulting product will
become crystalline and loose in value as the temperature of the electrolyte rises,
besides causing a great loss of electrical energy. While the anodes must always
consist of metallic lead "Kathodes" of lead, platinum, carbon or any other suitable
material may be used. I will illustrate the reactions which take place when a
solution of acetate of soda and bi-carbonate of soda is employed:
At the negative pole (Anode) free acetic acid is formed which dissolves the lead
as acetate of lead, carbonic acid being set free at the same time from the bi-carbonate;
at the positive pole (Kathode) free caustic soda is formed, both from the acetate and
from the bi-carbonate of soda. As the liquid is constantly circulating by means
of the carbonic acid gas which is injected into the electrolyte near the bottom of the
cell, the solutions of acetate of lead and caustic soda come into contact as quickly as
forined in the presence of the carbonic acid, liberated at the Anode, and the following
reactions take place:
:-

page_text: II.
2 NaOH combine with 2 CO₂ which is supplied as gas and regenerate
2 NaOH. CO₂
It will be seen that both the acetate and bi-carbonate are continuously regenerated,
the process consuming only lead, carbonic acid and water which are regularly
supplied.
The proper proportions to use for the electrolyte solutions are 4 parts of acetate,
nitrate or other salt of Soda, Potash or Ammonia and 1 part of bi-carbonate, which
proportions correspond sufficiently exact to the molecular weights in the reaction
shown above. I prefer to use the salts of Ammonia, as these require only an electro-
motive force of 0,7 Volt while the Potassium and Sodium salts require an average of
four Volts. I prefer also that the electrolyte solution should contain more than
5% (five per cent.) of the said salt or salts.
Having thus described the object and nature of my invention and in what manner
the same may be put in practice, I wish it to be understood that I do not claim all
the details specified as to the percentage of the electrolyte or the strength of current
employed and the like, as they may be greatly varied without departing from the
spirit of my invention, but I claim as new and essential features of the same :
I. The process of producing white lead by electrolysis consisting in passing an
electric current from an anode of metallic lead through an alkaline electrolyte
consisting of a solution of a salt of ammonia in combination with any acid, which will
produce a soluble lead salt in the sense of this invention, and of a bi-carbonate of
an alkali, to a kathode of lead, carbon or any other suitable material, thereby causing
a decomposition of the salts in the electrolyte, and a formation of a soluble compound
of lead, which is transformed into the hydrated carbonate of lead by the simultaneous
generation of free carbonic acid at the said anode and by the presence of caustic alkali
(ammonia) at the said kathode, passing a current of carbonic acid gas through said
electrolyte to regenerate the spent alkaline bi-carbonate until said anode is completely
dissolved.
II. The process of producing white lead which consists in passing an electric
current from an anode of metallic lead through an alkaline electrolyte consisting of a
solution of a salt of an alkali in combination with any acid which will produce a
soluble lead salt in the sense of this invention, and of a bi-carbonate of an alkali, said
solution to contain more than 5% of said salt or salts, to a kathode of lead, carbon or
any other suitable material, thereby causing a decomposition of the salts in the
electrolyte and a formation of a soluble compound of lead, which is transformed into
the hydrated carbonate of lead by the simultaneous generation of free carbonic acid
at the said anode and by the presence of caustic alkali generated at said kathode,
passing a current of carbonic acid gas through said electrolyte to regenerate the
spent alkaline bi-carbonate until said anode is completely dissolved, all for the purpose
as set forth and described.