AN IMPROVED METHOD OF PRODUCING WHITE PIGMENTS FROM LEAD
Year: 1869

page_text: LETTERS PATENT to John Gallemore Dale and Edward Milner,, of
Warrington, in the County of Lancaster, for the Invention of
- D
T
Sealed the 11th February 1870, and dated the 16th August 1869.
PROVISIONAL SPECIFICATION left by the said John Gallemore Dale
and Edward Milner at the Office of the Commissioners of Patents,
with their Petition, on the 16th August 1869.
We, JOHN GALLEMORE DALE and EDWARD MILNER, of Warrington,,
in the County of Lancaster, do hereby declare the nature of the said:
Invention for "AN IMPROVED METHOD OF PRODUCING WHITE PIGMENTS FROM
LEAD," to be as follows:-
Our Invention relates to the production of carbonate of lead by the
action of soluble acid carbonates of the alkaline metals and alkaline
earths on the oxides of lead or basic salts of lead.
We propose to carry out our Invention in two ways,―
1. We mix litharge, hydrated oxides of lead, or basic salts of lead
with an equivalent of bi-carbonate of soda together with sufficient water

page_text: to form a stiffish paste; this is then ground in a suitable mill until the
change of the lead bodies into carbonate is complete. The supernatant
liquor, which consists of mono-carbonate of soda, may either be boiled
down to dryness and disposed of as soda ash, or heated with carbonic
acid to form a further quantity of bi-carbonate of soda, which may be
used to convert a further quantity of lead oxides as set forth.
2. We mix litharge, hydrated oxides of lead, or basic salts of lead
with caustic soda, mono-carbonate of soda, or acid carbonates of soda
with sufficient water to form a stiffish paste; the mixture is then
introduced into a suitably closed mill, and during the grinding a stream
of carbonic acid is passed into it. After conversion of the lead bodies
into carbonate the supernatant fluid may be heated as before described.
In carrying out the process by this secondly described method we do
not bind ourselves to any particular proportions of lead oxides and soda,
but may observe that equivalents of each answer very well, but the
quantities of soda salts may be reduced with success if desirable.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Gallemore Dale and Edward Milner in the
Great Seal Patent Office on the 16th February 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JOHN
GALLEMORE DALE and EDWARD MILNER, of Warrington, in the County.
of Lancaster, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of August, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty--
third year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said John Gallemore Dale and Edward
Milner, Her special licence that we, the said John Gallemore Dale and
Edward Milner, our executors, administrators, and assigns, or such
others as we, the said John Gallemore Dale and Edward Milner, our
executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use,
excrcise, and vend, within the United Kingdom of Great Britain and

page_text: Ireland, the Channel Islands, and Isle of Man, an Invention for "AN
IMPROVED METHOD OF PRODUCING WHITE PIGMENTS PROM LEAD," upon the con-
dition (amongst others) that we, the said John Gallemore Dale and
Edward Milner, our executors or administrators, by an instrument in
writing under our, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said John Gallemore Dale and Edward
Milner, do hereby declare the nature of our said Invention, and in what
manner the same is to be performed, to be particularly described and
ascertained in and by the following statement, that is to say: - .
Our Invention relates to an improved method of manufacturing white
lead, "carbonate of lead" by the action of the soluble acid carbonates
of the alkalies on litharge, hydrated oxides of lead, or insoluble basic
salts of lead.
We propose to carry out our Invention in two ways, and when soda
is the substance chosen we proceed,-
First., By mixing litharge, hydrated oxides of lead, or insoluble basic
salts of lead, with an equivalent of bi-carbonate of soda, together with
sufficient water to form a stiffish paste; this mixture is ground in a
suitable mill, small quantities of water being from time to time added
as may be found requisite until the change of the lead bodies into car-
bonates is complete. The paste is now well washed with water, and the
supernatant liquid which contains mono-carbonate of soda, is separated
from the white lead by filtration and boiled down to dryness and
disposed of as soda ash, or it may be crystallized or may be again
converted into bi-carbonate of soda by treatment with carbonic acid,
and used to convert further quantities of lead oxides or insoluble basic
salts of lead, into carbonates. Instead of grinding, the lead oxides or
insoluble basic salts of lead in a fine state of division may simply be
mixed with bi-carbonate of soda and water and left to themselves, wben
the conversion into carbonates goes on in the same manner only much
more slowly.
Secondly. We mix litharge, hydrated oxides of lead, or basic salts of
lead with caustic soda, mono-carbonate of soda, or acid carbonates of
soda and sufficient water to form a stiffish paste; the mixture is now

page_text: introduced into a suitable closed mill, and during the grinding a stream
of carbonic acid gas is passed into it. After conversion of the lead
bodies into carbonates they are washed with water and the supernatant
liquid treated as before described.
In carrying out our process by this secondly described method we
do not bind ourselves to any particular proportion of lead oxides and
soda but may say that equivalents of each answer very well. The
quantity of the soda salts may however be reduced with advantage if
found desirable. Grinding may also be dispensed with by mixing the
lead oxides or insoluble basic salts of lead in a fine state of division
with the caustic soda, mono-carbonate or acid carbonates of soda, as
described, and exposing the mixture in a suitable room to the action of
carbonic acid. We may say that artificial heat accelerates the con-
version both in the first and secondly described operations, but is not
essential to their success.
Having now described the nature and particulars of our said Invention
and the manner in which the same is to be performed, we desire it to be
understood that we claim, the manufacture of carbonate of lead by the
action of acid carbonates of the alkalies on litharge, hydrated oxides of
lead, and insoluble basic salts of lead, either by direct addition as de-
scribed in our first part or indirectly by the mixture of the lead oxides
with the caustic alkalies or their mono-carbonate or acid salts and
their conversion into bi-carbonates during the time they are in contact
with the litharge, hydrated oxides, or insoluble basic salts of lead.
In witness whereof, I, the said Edward Milner, for and on behalf
of myself, and the said John Gallemore Dale, have hereunto set
my hand and seal, this Tenth day of February, in the year of
our Lord One thousand eight hundred and seventy.
EDWARD MILNER. (L.S.)