IMPROVEMENTS IN THE METHOD OF PRODUCING WHITE PIGMENTS FROM LEAD
Year: 1872

page_text: LETTERS PATENT to Edward Milner, of Springfield, Warrington, in
the County of Lancaster, Salt Manufacturer, for the Invention of
"IMPROVEMENTS IN THE METHOD OF PRODUCING WHITE PIGMENTS FROM
LEAD."
Sealed the 13th August 1872, and dated the 22nd June 1872.
PROVISIONAL SPECIFICATION left by the said Edward Milner at the
Office of the Commissioners of Patents, with his Petition, on the
22nd June 1872.
I, EDWARD MILNER, of Springfield, Warrington, in the County of
Lancaster, Salt Manufacturer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE METHOD OF PRODUCING WHITE PIGMENTS
FROM LEAD," to be as follows:-
My Invention relates to an improved method of manufacturing white
lead, "carbonate of lead" from litharge, and is a further improvement
based on the process described in the Specification of Letters Patent
granted to John Gallemore Dale and myself, the said Edward Milner,
dated August 16th, 1869.

page_text: 1. I take the oxide of lead (commonly known as litharge) in a finely
ground state, and mix it with a solution of the chlorides of sodium,
potassium, or ammonium, and put the mixture into constant agitation
for a few hours. The result is a liquid containing in suspension an
exceedingly white flocculent compound consisting of hydrated oxide and
chloride of lead, and when common salt is used a quantity of caustic
soda in solution.
.
2. Into the mixture so formed, and preferably in the same vessel,
I then pass a current of carbonic acid and violently agitate it. This I
continue until the solution no longer gives an alkaline reaction, and
the product is a nearly pure carbonate of lead of great body and opacity,
which only needs washing to free it from salts, and is then ready to
be dried and used for all the purposes to which white lead is applied.
I find that 30 to 40 parts of water to 10 parts of litharge and 1 of
common salt answer, well, but I do not consider those precise proportions
essential.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Edward Milner in the Great Seal Patent Office
on the 17th December 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
MILNER, of Springfield, Warrington, in the County of Lancaster, Salt
Manufacturer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-second day of June, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Edward Milner, Her special licence that
I, the said Edward Milner, my executors, administrators, and assigns, or
:such others as I, the said Edward Milner,, my 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, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN THE METHOD OF
PRODUCING WHITE PIGMENTS FROM LEAD," upon the condition. (amongst

page_text: others) that I, the said Edward Milner, my executors or administrators,
by an instrument in writing under my, 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.
i
NOW KNOW YE, that I, the said Edward Milner, do hereby declare
the nature of my 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 :-
My Invention relates to an improved method of manufacturing white
lead, "carbonate of lead" from litharge, and is a further improvement
based on the process described in the Specification of Letters Patent
granted to John Gallemore Dale and myself, the said Edward Milner,
dated August 16th, 1869.
1. I take the oxide of lead (commonly known as litharge) in a finely
ground state, and mix it with a solution of the chlorides of sodium,
potassium, or ammonium, and put the mixture into a state of constant
agitation for a few hours. The result is a liquid containing in suspension
an exceedingly white flocculent compound consisting of hydrated oxide
and chloride of lead, and when common salt is used a quantity of caustic
soda in solution.
2. Into the mixture so formed, and in the same vessel, I then pass a
current of carbonic acid and violently agitate it. This I continue until
the solution no longer gives an alkaline reaction, and the product is a
nearly pure carbonate of lead of great body and opacity, which only
needs washing to free it from salts, and is then ready to be dried
and used for all the purposes to which white lcad is applied. I find
that 30 to 40 parts of water to 10 parts of litharge and 1 of common
salt answer well, but I do not consider those precise proportions
essential.
3. Or instead of using the same vessel in which the first part of the
process is carried out for the subsequent operation I run the mixture
into a vessel having an air-tight cover, and introduce the carbonic acid
gas into the mixture by means of a pump or other apparatus, the gas
being introduced into the mixture at the bottom or some low point. By

page_text: this means I obtain a gradually increasing pressure, and consequently a
more rapid and perfect absorption of the gas.
"
"
I claim the manufacture of "white lead" or carbonate of lead by
treating a mixture composed of lithargé and chloride of ammonium or
of potassium or of sodium with carbonic acid gas, either under pressure
or in an open vessel, substantially as described.
In witness whereof, I, the said Edward Milner, have hereunto set
my hand and seal, this Fourteenth day of December, in the year
of our Lord One thousand eight 'hundred and seventy-two.
Signed, sealed, and delivered by the
above-named Edward Milner, in
the presence of
G. A. F. BERTIE,
EDWARD MILNER. (L.S.)
Clerk to Messrs. Gregory, & Co.,
Solrs.,
1, Bedford Row,
London.