A NEW OR IMPROVED MANUFACTURE OF A YELLOW PIGMENT
Year: 1858

page_text: LETTERS PATENT to Allan Dick, of Holywell, in the County of Flint,
Metallurgist, for the Invention of "A NEW OR IMPROVED MANUFACTURE
OF A YELLOW PIGMENT."
PROVISIONAL SPECIFICATION left by the said Allan Dick at the
Office of the Commissioners of Patents, with his Petition, on the
15th November '1858.
I, ALLAN DICK, of Holywell, in the County of Flint, Metallurgist, do hereby
declare the nature of the said Invention for "A NEW OR IMPROVED MANUFACTURE
OF A YELLOW PIGMENT," to be as follows:-
My Invention consists in manufacturing a yellow pigment from the dross
or oxide formed in the process of softening lead, as herein-after described.
In the softening of lead the said lead is exposed to the action of heat and air
by preference in a reverberatory furnace; the antimony and other impurities
contained in the lead are oxidized, and the dross formed on the surface of the
melted lead consists essentially of oxide of lead and oxide of antimony. I
reduce the said dross or mixed oxides to a fine powder by grinding and calcine
the said powder, beginning at a low heat and raising the temperature to a red
heat. I prefer to add to and mix with the powder during the latter part of
the calcining process a quantity of common salt; the exact quantity is not
material, but a quantity not exceeding one-half the weight of the powdered
oxide I have found to answer very well. Although I prefer to add salt as

page_text: described, yet I do confine myself thereto, as the yellow color is produced in
the dross or mixed oxides by the action of heat alone, but the quality of the
pigment is improved when salt is employed. After the full effect of the heat,
or of the heat combined with the action of salt has been produced, the powder
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Allan Dick in the Great Seal Patent Office on the
29th April 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALLAN
DICK, of Holywell, in the County of Flint, Metallurgist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters.
Patent, bearing date the Fifteenth day of November, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Allan Dick, Her special licence that I, the said Allan Dick, my
executors, administrators, and assigns, or such others as I, the said Allan
Dick, 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 "A NEW OR IMPROVED MANU-
PACTURE OF A YELLOW PIGMENT," upon the condition (amongst others) that I,
the said Allan Dick, my executors or administrators, by an instrument in
writing under my, or their, or one of their hands and seals, should par-
ticularly 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 I, the said Allan Dick, do hereby declare the
nature of the said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement
thereof, that is to say:-
My Invention consists in manufacturing a yellow pigment in the manner
herein-after described from the dross or oxide formed in the process of
softening lead. In the said process of softening lead the lead to be softened is
exposed to the action of heat and air by being melted in a reverberatory or

page_text: other furnace, in which a large surface of the metal melted therein is
exposed to the action of the air. By this treatment the antimony and other
metals contained in the lead are oxidized, and the oxides of the said metals
form a dross or scum on the surface of the melted lead. The said dross,
scum, or oxide consists essentially of oxides of lead, antimony, and arsenic.
In manufacturing a yellow pigment from the said dross, scum, or oxide, I
reduce it to a fine powder by grinding, and I calcine the said powder in a
reverberatory furnace, or in any other manner by which the said powder may
be exposed to the joint action of heat and air. I begin the calcination at a
low heat or a heat below redness, and raise the heat to redness during the
process. The time during which the calcination must be prolonged depends
upon the quantity of material operated upon. I have found in practice, that
when operating upon thirty, hundredweight of the powdered dross, a calci-
nation of from one to three days is sufficient. I prefer to add and mix with
the powder during the latter part of the calcining process a quantity of chloride
of sodium or common salt. The exact relative quantity of the said salt is not
material, but a quantity not exceeding one-half the weight of the powdered
oxide I have found to answer well in practice. After calcining the said dross
or powder, I sometimes saturate it with sulphuric acid or with muriatic acid
or with acetic acid, or expose the said powdered dross or oxide to the vapour
of acetic acid in stacks of bark, after the manner practised in the manufacture
of white lead. I do not, however, confine myself to the manufacture of a
yellow pigment from the dross or oxide when treated with common salt, or
sulphuric acid, or muriatic acid, or acetic acid, or vapour of acetic acid, as a
yellow pigment may be produced by heating the said dross or oxide in contact
with air, but the quality of the pigment is improved by the use of common salt
or the acids herein-before described. After the full effect of the heat has been
produced, and the quality of the pigment no longer improves, the powder is
removed from the furnace and washed and ground, when its manufacture is
complete.
Having now described the nature of my said Invention, and the manner of
carrying the same into effect, I wish it to be understood that I do not limit
myself to the precise details herein described, as the same may be varied
without departing from the nature of my Invention, but I claim as my
Invention the new or improved manufacture of a yellow pigment herein-before
described, that is to say, manufacturing a yellow pigment from the dross or
oxide produced in the process of softening lead, by heating the said dross or
oxide in contact with air, whether the said dross or oxide be treated with
common salt or any of the acids herein-before enumerated, before, during, or

page_text: after the heating, or be heated without the use of common salt or any of the
said acids.
In witness whereof, I, the said Allan Dick, have hereunto set my hand
and seal, this Twenty-fifth day of April, in the year of our Lord One
thousand eight hundred and fifty-nine.
Witness,
ALFRED OSTEN WALKER.
ALLAN DICK. (L.S.)