Improvements in the Manufacture of White Lead.
Year: 1891

page_text: Date of Application, 18th Apr., 1991
Complete Specification Left, 16th Jan., 1892-Accepted, 16th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of White Lead.
I ROBERT JAMES WHITE of the Lead and Zine White Works Chatham Street
Grosvenor Street Camberwell in the County of Surrey Manufacturer do hereby
declare the nature of this invention to be as follows:-
My invention consists in submitting metallic lead cast into any convenient form
of all pieces to the action of a weak solution of acetic acid or acetate or other
suitable salt of lead in water and at the same time to the action of carbonic acid
gas, and oxygen or atmospheric air the solution or the atmosphere surrounding the
lead being maintained at a temperature of 100 to 120 degrees Fahrenheit more or
less and further passing the solution as hot as possible and carrying with it more
or less of the white lead in mechanical suspension again over the metal without the
carbonic acid gas but exposed to atmospheric air until analysis or experience shews
the white lead to contain the due proportion of hydrated oxide to the neutral
carbonate.
The metallic lead may be placed in closed oblong rectangular stacks or racks
the bottom of each of which is raised considerably towards the middle forming a
ridge from end to end and constructed to allow the solution to pass through.
Openings closed with shutters are formed in the sides which permit the lead
being cleared from the sloping bottom from time to time. Each rack is placed
over or in a suitable back or tray and the solution distributed over the lead which
is fed in upon the top.
The lead may also be submitted for corrosion in a perforated case or cage
revolving partly immersed in a vat containing the solution the revolving cage being
closely covered in and provision made both in this and the fixed racks for carbonie
acid gas and atmospheric air to enter or to be forced in. In place of the metallic
lead litharge may be employed and operated upon by any of the well known
methods the action of the carbonic acid gas being continued until an excess of
neutral carbonate of lead is produced in the white lead deposited. A quantity of
the lead solution carrying with it a portion of the white lead is then alternately
passed over metallic lead and passed over or mixed with the white lead as and for
the purpose described above when the white lead is produced directly from the
metal.
After drying the white lead is crushed or condensed under edge runners or other
suitable crushing machinery.
ROBERT J. WHITE.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of White Lead.
1, ROBERT JAMES WHITE, of the Lead and Zinc White Works, Chatham
Street, Grosvenor Street, Camberwell, in the County of Surrey, Manufacturer, do
hereby declare the nature of the said invention and in what manner the same is to
he performed to be particularly described and ascertained in and by the following
statement :-
It is well known that carbonate of lead produced by any of the so-called
precipitation or wet processes is deficient in body or covering power when ground
in oil to produce paint. Various attempts have been male from time to time to
impart body or covering power or opacity to such carbonate of lead so as to make
it equal to white lead of the best quality; but so far as I am aware these attempts

page_text: have as a rule failed or have only been partially successful. The object of my
present invention is to provide means whereby the required body, covering power
or opacity can be imparted to any carbonate of lead that is deficient in those
qualities, and my said invention consists in enriching such lead carbonate by treat-
ing it with a hot saturated lead solution which is passed alternately over metallic
lead or over lead oxide exposed to atmospheric air or oxygen and over or amongst
the lead carbonate under treatment, the operation being continued until the white
lead so treated is found to possess the required chemical composition composed say
of two equivalents of neutral carbonate of lead and one of hydrated oxide of lead.
In carrying my invention into effect I prefer to operate upon lead carbonate
produced in the following manner namely:
Metallic lead, cast or otherwise divided into small pieces of any convenient form
is submitted to the action of a weak solution of acetic acid or of acetate or other
suitable salt of lead in water, and at the same time to the action of carbonic acid
gas and oxygen or atmospheric air, the solution, or the atmosphere, or both,
surrounding the lead being maintained at a temperature of 100° to 120° Fahrenheit
more or less. By these means which are well known and to which I make no
claim, any desired quantity of lead carbonate can be produced but which is deficient
in body or opacity as above described. I then pass the said solution, made as hot
as possible and carrying with it or not more or less of the lead carbonate in
nechanical suspension, again and again over the metallic lead without the presence
of carbonic acid gas, but exposed to atmospheric air or other suitable oxidizing
medium, and then pass the said solution after each passage over the metallic lead,
over or through the whole mass of lead carbonate that has to be treated until
analysis or experience shows the white lead to contain the due proportion of
chemical constituents that is to say two equivalents of neutral carbonate and one of
hydrated oxide of lead.
If preferred or found more convenient the carbonate of lead may be separated
from the solution by which it has been produced, and be treated as above described
with other lead solution passed again and again over metallic lead or litharge.
Whichever method be adopted the essential feature of the invention consists in
treating carbonate of lead containing an excess of carbonic acid with a lead solution
kept saturated by being passed over metallic lead or litharge whereby the carbonate
of lead has imparted to it the due proportion of the hydrated oxide, and when the
proper quantity of the hydrated oxide has been combined with the carbonate the
latter will not take up any more, however long the process may be continued, so
that there is no danger of carrying the process too far, and the process is to that
extent automatic or self-regulating.
It is obvious that the carbonate of lead intended to be operated upon by my
above described process may be produced by any other means than that above
described, for example, it may be produced by any of the well known precipitation
processes and either direct from metallic lead or from litharge, or white lead
produced by any process whatever but which is deficient in body or opacity may
be enriched by those qualities being imparted to it by passing a sufficient quantity
of saturated lead solution over or through it.
The metallic lead in a sufficiently divided state may be treated in closed oblong
rectangular stacks or racks, such as that shown in the drawings hereto annexed, in
which Figure 1 is a longitudinal section, Figure 2 a plan with the top and some of
the cross bars removed, and Figure 3 a transverse section. The bottom A of this
stack or rack is perforated or formed of separate bars as shown, and raised towards
the middle so as to form a ridge from end to end of the chamber B, and con-
structed to allow the solution and product to pass through it into the tank or tray C
in which the apparatus stands. Suitable openings with shutters D are formed in
the sides of the chamber B to enable the lead to be cleared from the sloping
bottom A, if and when required. E are cross bars intended to assist in carrying
the weight of the lead under treatment in order to keep it in a separated and open
condition, to facilitate the passage of the solution through it, and also to prevent

page_text: the entire weight from coming on the bottom A. The solution is distributed over
the lead by sparge pipes at the top of the chamber. and fresh lead is introduced
through openings at the top of the chamber from time to time as that in the
chamber is dissolved.
The carbonic acid gas and atmospheric air may be admitted through the pipe F
which may be furnished with a number of holes for their uniform distribution
throughout the chamber.
The solution may be withdrawn from the tank or tray C and returned to the
upper part of the chamber B by a pump or otherwise both during the operation of
making the lead carbonate and during that of treating the carbonate with heated
lead solution, suitable apparatus being provided for heating the said solution on its
way from the said tank or tray to the upper part of the chamber B.
If preferred the metallic lead or litharge may be submitted to corrosion in a
perforated case or cage revolving partly immersed in a vat containing the solution.
the revolving cage being closely covered in and provision made for carbonic acid
gas and atmospheric air to enter or to be forced in, but I make no claim to
apparatus of this latter kind as it is well known in the art of white lead
making.
The action of the carbonic acid gas is preferably continued, whether metallic
lead or litharge be used, until an excess of carbonic acid is produced in the white lead
deposited. I prefer to apply the carbonic acid gas in contact with the metallic
lead or litharge as described, as I obtain a more rapid corrosion; but the carbonate
or white lead may be precipitated from a basic lead solution by carbonic acid gas
applied in a separate vessel as is ordinarily practised, the white lead produced being
afterwards treated as above described with a heated basic solution of lead obtained
either from dissolved litharge or directly from the metal until the desired composi-
tion of the white lead is obtained.
Instead of a solution of acetic acid or of acetate of lead being employed, a
solution of nitric acid or of nitrate of lead may be used.
After drying, the white lead is crushed or condensed under edge runners or
other suitable crushing machinery in the usual way.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed I desire to have it
understood that I make no claim generally to the production of white lead by
treating a solution of lead with carbonic acid gas in presence of metallic lead or
litharge, but that what I do claim is :-
First. The improved manufacture of white lead substantially as hereinbefore
described.
Second. In the manufacture of white lead enriching the products by treating
white lead such as is produced by precipitation by means of carbonic acid gas,
with heated lead solution, substantially as hereinbefore described, and for the
purpose specified.
Third. In the manufacture of white lead, the use of apparatus consisting of a
closed chamber having a perforated sloping bottom with openings and shutters for
clearing out the lead, cross bars to assist in supporting the weight of the lead, and
to keep the same in a more or less separated and open condition, a tank or tray to
receive the solution and product and in which the apparatus stands, and suitable
pipes for the inlet of carbonic acid and air and solution, all combined, arranged,
and operating, substantially as hereinbefore described, and illustrated in the
drawings.
D
1938