Improvements in or relating to the Manufacture of White Lead.
Year: 1888

page_text: Date of Application, 21st Dec., 1888
Complete Specification Left, 9th Sept., 1889-Accepted, 9th Nov., 1889
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Manufacture of White Lead.
I, HENRY BOLLMANN CONDY of Ford's Folly, Church Road Battersea in the
County of Surrey Manufacturing Chemist do hereby declare the nature of this inven-
tion to be as follows:-
This invention relates to the manufacture of white lead and more especially to the
process in which a basic acetate of lead is produced and converted into white
lead.
The object of the present invention is to so improve this process that a better result
may be obtained than heretofore and at less cost by reason of the special materials
employed and the by-products obtained by the use of the same and the recovery of
substantially all the material (which may not have been chemically or so to speak
usefully employed in the composition of the white lead itself) in a form suitable for
using again.
To this end the invention consists in the process hereinafter described that is to say
the consecutive employment of the various stages hereinafter enumerated by means
of which the said result is obtained.
In carrying out this improved process I at first proceed substantially as shown in
the specification of Letters Patent No. 1693 of 1884 namely, Metallic lead is care-
fully granulated by melting and pouring it into water, and a vat or vats is filled
therewith. Above the level of the said vat or vats is another vat in which dilute
acetic acid is placed, the proportion being about 55 lbs. of acetic acid containing 40%
of hydrated acetic acid to about 625 lbs. of water. This vat is connected to the
former vat or vats by pipes provided with cocks so that the liquor may be run onto
the metallic lead and turned on and off at will. After allowing the acid to run onto
the lead and remain in contact therewith for a period of from 4 to 6 hours the liquor
is run off into a vat placed at a lower level so that the lead is left exposed to the
atmospheric air which enters the vat, and the lead is oxidized thereby.
The liquor which has run through the lead is pumped up into another vat above the
level of the lead and after the lead has become sufficiently oxidized, which will
usually occur in from 4 to 6 hours, the same liquor is again run onto the lead,
and the coating of oxide or a great part thereof is dissolved therein and removed
thereby.
This operation of alternate oxidation of the lead by atmospheric air and solution of
the oxidized lead is repeated until the specific gravity of the liquor reaches 1·145 or
thereabouts. At this stage I pump the liquor into a closed tank or vat fitted with
an agitator driven by power which is kept constantly in action until the operation is
completed.
Carbonic acid gas is driven into this vat until it is found by testing a small sample
drawn from the bulk or otherwise that the contents of the vat have become neutral at
which stage the white lead must be separated by means of filtration, pressure or other-
wise from the liquor in which it has been precipitated. The liquor thus separated is
again treated with carbonic acid until it appears upon testing a small sample drawn
from the bulk to give no further precipitate or only a slight cloudiness with further
treatment by carbonic acid.
The precipitate resulting from the first operation treated as hereinafter described
that from the second operation is added to the next batch of basic acetate of lead made
and well agitated therein before the treatment of this next batch with carbonic acid
gas. By this treatment I obtain a better product because the white lead as made in
the second operation (without this treatment) is not so easy to spread when ground
into paint.

page_text: As a part of my improved process I prefer to make carbonic acid gas by heating
bicarbonate of soda in a closed retort by which proceeding I obtain the advantage
that the bye product namely carbonate of soda, which is the residue I obtain, has a
value equal or nearly equal to the original cost of the bicarbonate of soda.
Or I may obtain the necessary carbonic acid by or from the chimney smoke well
washed and cooled previously to being forced into the lead liquor, by which
method I may obtain carbonic acid gas practically free of expense from the factory
chimney.
After the second treatment with carbonic acid the liquor will be found to be dis-
tinctly acid and after being filtered, decanted or pressed out of the precipitated white
lead, it can be re-employed for dissolving fresh lead it being if necessary fortified by
the addition of more acetic acid to bring it up to the required strength.
The white lead from the first operation with the carbonic acid gas should be taken
out of the filters or presses, thrown slowly into a vat full of water which may be
kept heated and fitted with an agitator kept in motion. When the lead is well sus-
pended in the water an alkali or alkaline earth or carbonate of alkali is gradually
added until the liquid shows by testing a small sample that the small quantity of lead
contained in the solution is precipitated. The white lead is then separated (and to
effect this object I prefer to use a filter press) and dried in the usual way. The
separated liquor is evaporated and the acetate of the alkali or alkaline earth is
recovered in a form suitable for commerce or for reemployment in the manufacture
of acetic acid, for white lead making or for other purposes.
The alkali I prefer to use is soda or the alkaline earth lime. As a carbonate I prefer
to use that of soda.
1000
COMPLETE SPECIFICATION.
Improvements in or relating to the Manufacture of White Lead.
I HENRY BOLLMANN CONDY of Fords Folly, Battersea in the County of Surrey,
Manufacturing 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 :-
This invention relates to the manufacture of white lead and more especially to the
process in which a basic acetate of lead is produced and converted into white
lead.
The object of the present invention is to so improve this process that a better
result may be obtained than heretofore and at less cost by reason of the special
materials employed and the bye products obtained by the use of the same and the
recovery of substantially all the material (which may not have been chemically or so
to speak usefully employed in the composition of white lead itself) in a form suitable
for using again.
To this end the invention consists in the process hereinafter described, that is to say,
the consecutive employment of the various stages hereinafter enumerated by means of
which the said result is obtained.
In carrying out this improved process, I at first proceed substantially as shown in
the specification of Letters Patent No. 1693 of 1884 namely
Metallic lead is carefully granulated by melting and pouring it into water and a
vat or vats is filled therewith. Above the level of the said vat or vats is another vat
in which dilute acetic acid is placed, the proportion being about 55 lbs. of acetic acid,
containing 40% of hydrated acetic acid to about 625 lbs. of water.
This vat is connected to the former vat or vats by pipes provided with cocks so
that the liquor may be run onto the metallic lead and turned on and off at will. After
allowing the acid to run onto the lead and remain in contact therewith for a period
of from 4 to 6 hours the liquor is run off into a vat placed at a lower level so that

page_text: the lead is left exposed to the atmospheric air which enters the vat and the lead is
oxydised thereby.
The liquor which has run through the lead is pumped up into another vat above the
level of the lead and after the lead has become sufficiently oxidised which will usually
occur in from 4 to 6 hours the same liquor is again run onto the lead and the coating
of oxide or a great part thereof is dissolved therein and removed thereby. This
operation of alternate oxidisation of the lead by atmospheric air and solution of the
oxydised lead is repeated until the specific gravity of the liquor reaches 1-145 or there-
abouts. At this stage I pump the liquor into a closed tank or vat, fitted with an
agitator driven by power which is kept constantly in action until the operation is
completed.
Carbonic acid gas is driven into this vat until it is found by testing a small sample
drawn from the bulk or otherwise, that the contents of the vat have become neutral, at
which stage, the white lead must be separated by means of filtration pressure or other-
wise from the liquor in which it has been precipitated. The liquor thus separated is
again treated with carbonic acid until it appears upon testing a small sample drawn
from the bulk to give no further precipitate or only a slight cloudiness with further
treatment by carbonic acid.
The precipitate resulting from the first operation is treated as hereinafter described,
that from the second operation is added to the next batch of basic acetate of lead
made and well agitated therein before the treatment of this next batch with carbonic
acid gas.
By this treatment I obtain a better product because. the white lead as made in
the second operation (without this treatment is not so easy to spread when ground
into paint.
As a part of my improved process I prefer to make carbonic acid gas by heating
bicarbonate of soda in a closed retort, by which proceeding I obtain the advantage
that the bye product namely carbonate of soda which is the residue I obtain has
a value equal or nearly equal to the original cost of the bicarbonate of soda.
Or I may obtain the necessary carbonic acid by or from the chimney smoke, well
washed and cooled previously to being forced into the lead liquor by which
method I may obtain carbonic acid gas practically free of expense from the factory
chimney.
After the second treatment with carbonic acid the liquor will be found to be dis-
tinctly acid and after being filtered decanted or pressed out of the precipitated white
lead, it can be re-employed for dissolving fresh lead, it being if necessary fortified by
the addition of more acetic acid to bring it up to the required strength.
•
The white lead from the first operation with carbonic acid gas, should be taken out
of the filters or presses, thrown slowly into a vat full of water, which may be kept
heated and fitted with an agitator kept in motion. When the lead is well suspended
in the water an alkali or alkaline earth or carbonate of alkali is gradually added until
the liquid shows, by testing a small sample, that the small quantity of lead contained
in the solution is precipitated.
or for
The white lead is then separated (and to effect this is prefer to use a filter press)
and dried in the usual way. The separated liquor is evaporated and the acetate of the
alkali or alkaline earth is recovered in a form suitable for commerce
re-employment in the manufacture of acetic acid for white lead making or for
other purposes.
The alkali I prefer to use is soda, and the alkaline earth lime. As a carbonate 1
prefer to use that of soda.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is
In the manufacture of white lead.
1. The method consisting in alternately oxidising metallic lead by atmospheric air
11
1
1

page_text: by carbonic acid gas until the solution is rendered neutral and removing the pre-
cipitated white lead therefrom at this stage.
2. The method consisting in forming tribasic acetate of lead in solution, treating
the same, with carbonic acid gas until the solution is rendered neutral and removing
the precipitated white lead at this stage.
3. The method consisting in forming tribasic acetate of lead in solution, treating
the same with carbonic acid gas until the solution is rendered neutral, removing the
precipitated white lead at this stage, continuing the treatment with carbonic acid gas,
removing the second batch of precipitated white lead and adding the latter to the
next batch of acetate of lead in solution before treatment of the same with carbonic
acid gas.
4. The method consisting in forming tribasic acetate of lead in solution, treating
the same with carbonic acid gas, until the solution is rendered neutral, removing the
white lead precipitated at this stage, and washing the same in water containing an
alkaline matter.
DATOR U way
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.