Improvements in or relating to the Treatment of White Lead.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to the Treatment of White Lead.
I, THOMAS CRISP SANDERSON, of Brooklyn, Humber Road, Westcombe Park,
London, S.E., Manufacturing Chemist, do hereby declare the nature of this inven-
tion to be as follows:-
:-
My invention consists of an improved method of dealing with white lead,
especially that which has undergone the process set forth in my application for
Letters Patent No. 6324 of 1897.
My present invention is devised to save the need for filtering, washing and dry-
ing the material before grinding with oil, whereby I not only economise time and
labour, but also avoid the risk of injury to the workpeople in these operations.
The precipitate is withdrawn from the vessel in which it is produced, together
with a quantity of the mother liquid, which consists of normal acetate of lead
solution, the whole is then passed through a settling tank so placed that whilst the
super-natant liquid can flow constantly away at the top, the precipitate pulpy white
lead can be also continuously removed at the bottom. In place of this, however,
I may run the whole into a settler and allow it to stand until the supernatant
liquid is clear; the clear liquid is then drawn off, and the pulpy precipitate can
then be removed. It is, however, preferable on a manufacturing scale, to separate
the pulp from the liquor in a centrifugal machine, through which a constant stream
of solution and precipitate is passed, and from which the clear mother liquor flows
away, whilst the pulpy white lead remains behind. The precipitate may then
be mixed without washing to rid it of remaining normal acetate of lead solution,
and treated in the manner described in my application for Letters Patent No. 11447
of 1898, directly with the necessary quantity of oil and be agitated until the white
lead and oil form into a mass leaving the acetate of lead solution separate and clear,
A small
This clear liquid can then be run off and return to the precipitation tank.
amount of solution may still remain inter-mixed throughout the mass, and may be
removed by continuing the agitation thereof with water.
I have found that about fifty gallons of water added in successive small quantities
is amply sufficient to wash one ton of the mixture, whereas, in treating the same
quantity of white lead which has been similarly filtered or deposited from the
mother liquor, from one thousand to fifteen hundred gallons of water is required
to wash it to the same degree of purity. After the washing water is run off from
the mass of oil and white lead, the latter may be at once ground through a mill in
the usual way.
It is better, however, to remove any small amount of water which
still remains therein before grinding, and this may be done in any convenient way,
as for instance, by warming the material in a vacuum pan with constant stirring
until the moisture is driven off. I prefer, however, to separate this moisture by
means of a centrifugal machine in the manner set forth in my Application
No. 11447 of 1898 above referred to, in which case special washing becomes unneces-
sary, as the small quantity of normal acetate solution which may remain is thus

page_text: practically completely removed, and the mixed mass remains ready to be ground
in a mill as usual.
By my improved method of operating, the cost of filtering and washing, handling
filter presses, and drying and handling the dry material is done away with, and
the white lead ready ground in oil is produced at a less cost than ordinary dry white
lead, and further all injury to workmen is prevented, there being no need to handle
wet material, and no production of dust.
Dated the 20th day of May 1800
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.
Improvements in or relating to the Treatment of White Lead,
I, THOMAS CRISP SANDERSON, of Brooklyn, Humber Road, Westcombe Park,
London, S.E., Manufacturing Chemist, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement-
My application for Letters l'atent relates to an improved method of dealing with
white lead in the manufacture of paints and the like.
Precipitated white lead which has undergone the process set forth in my previous
application for Letters Patent No. 6324 of 1897 is especially suitable for treatment
by this present process. The special object of my present invention is the saving
of the necessity for filtering, washing, and drying the material before grinding with
oil, by which means I attain considerable economy of time and of labour; beside
this I avoid the danger of injury to the health of the workmen involved in dealing
with the material in a condition in which it can evolve dust.
The precipitate is withdrawn from the vessel in which it is produced, together
with a quantity of the mother liquid, which consists of normal or even slightly
acid acetate of lead solution; the whole is then passed through a settling tank so
placed that whilst the super-natant liquid can flow constantly away at the top, the
precipitated pulpy white lead can be also continuously removed at the bottom. In
place of this, however, I may run the whole into a settler and allow it to stand until
the supernatant liquid is clear; the clear liquid is then drawn off, and the pulpy
precipitate can then be removed. It is, however, preferable on a manufacturing
scale to separate the pulp from the liquor in a centrifugal machine, through which
a constant stream of solution and precipitate is passed, and from which the clear
mother liquor flows away, whilst the pulpy white lead remains behind. The
precipitate may then, without washing to rid it of remaining normal acetate of lead
solution, be treated in the manner described in my application for Letters Patent
No. 11447 of 1898, directly with the necessary quantity of oil and be agitated until
the white lead and oil form into a mass leaving the acetate of lead solution separated
and clear. This clear liquid can then be run off and returned to the precipitation
tank. A small amount of solution may still remain intermixed throughout the
mass, and may be removed by continuing the agitation thereof with water.
I have found that about fifty gallons of water added in successive small quantities
is amply sufficient to wash one ton of the mixture, whereas, in treating the same
quantity of white lead which has been similarly filtered or deposited from the
mother liquor, from one thousand to fifteen hundred gallons of water is required
to wash it to the same degree of purity. After the washing water is run off from
the mass of oil and white lead, the latter may be at once ground through a mill

page_text: in the usual way. It is better, however, to remove any small amount of water
which still remains therein before grinding, and this may be done in any convenient
way, as for instance, by warming the material in a vacuum pan with constant
stirring until the moisture is driven off, or by enclosing the material in a bag or
cloth and pressing in the well-known manner used for expressing oils from seeds
and the like. I prefer, however, to separate this moisture by means of a centrifugal
machine in the manner set forth in my Application No. 11447 of 1898 above
referred to, in which case special washing becomes unnecessary, as the small
quantity of normal or even slightly acid acetate solution which may remain is thus
practically completely removed, and the mixed mass remains ready to be ground
in a mill as usual. "Or the mass may be subjected to mechanical pressure in a
suitable apparatus of any kind, until the excess of moisture is expelled.
By my improved method of operating, the cost of filtering and washing, handling
filter presses, and drying and handling the dry material is mostly done away with,
and the white lead ready ground in oil is produced at less cost than ordinary dry
white lead, and further all injury to workmen is prevented, there being no need
to handle wet material, and no production of dust.
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:-
1. The improvement in treating precipitated white lead consisting in separating
by gravity or by mechanical means the precipitate from the bulk of the mother
liquor, compounding the said precipitate with oil, and separating the expelled
solution and any excess of oil from the said compound substantially as described.
Dated the 23rd day of December 1898.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.