IMPROVEMENTS IN THE MANUFACTURE OF PIGMENTS FOR COATING SURFACES
Year: 1861

page_text: LETTERS PATENT to George Hallett, of 52, Broadwall, Lambeth, in the
County of Surrey, Antimony Refiner, and John Stenhouse, of 17, Rodney
Street, Pentonville, L.L.D., for the Invention of "IMPROVEMENTS IN THE
PROVISIONAL SPECIFICATION left by the said George Hallett and John
Stenhouse at the Office of the Commissioners of Patents, with their
Petition, on the 8th January 1861.
We, GEORGE HALLETT, of 52, Broadwall, Lambeth, in the County of Surrey,
Antimony Refiner, and JOHN STENHOUSE, of 17, Rodney Street, Pentonville,
L.L.D., do hereby declare the nature of the Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF PIGMENTS FOR COATING SURFACES," to be as follows:-
Our Invention has for its object improvements in the manufacture of
pigments for coating surfaces. For this purpose we employ native oxide of
antimony or such native oxide of antimony as may contain sulphide of
antimony, which is reduced to a fine powder, the impurities it contains,
derived from its matrix or gangue, are separated by picking and washing
as far as practicable. The finely powdered native oxide of antimony after
having been dried is calcined at a. red heat in open vessels or suitable
furnaces, with free access of air till any sulphur present has been expelled,

page_text: and the oxide has been converted into or chiefly into antimonious acid.
The calcined product consisting chiefly of antimonious acid is then ground
up with suitable oil or varnish, or other materials to admit of its being used
as a paint. When it is thought desirable other oxides, salts, or materials may
be combined with the calcined product, consisting chiefly of antimonious acid
thus prepared so as to form pigments suitable for the coating of surfaces. We
likewise employ the native oxide of antimony or such native oxide of antimony
as may contain sulphide of antimony, and the more or less pure antimonious
acid obtained from them by the process above described for the manufacture
of a yellow pigment. This we produce by taking eight parts of either native
oxide of antimony or such native oxide of antimony as may contain sulphide
of antimony or antimonious acid more or less pure, three parts of either red
lead or litharge (or two and a half parts of carbonate of lead) one part of
oxide of zinc and four parts of common salt. These are all intimately mixed
in a state of fine powder, and are then calcined at a red heat in suitable
vessels or furnaces till a combination is effected and the yellow pigment is
produced. When this has been accomplished the mass is reduced to fine
powder and washed with water till all the common salt is removed. When
dried a yellow powder is obtained. We do not confine ourselves to the
quantities of the different materials above described, but the proportions
mentioned are found to answer very well. Sometimes we increase the quantity
of oxide or carbonate of lead, and at others omit the oxide of zinc altogether,
and by varying the proportions of the ingredients, Naples yellow is obtained
of different shades of color.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Hallett and John Stenhouse in the Great Seal Patent
Office on the 8th July 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, GEORGE
HALLETT, of 52, Broadwall, Lambeth, in the County of Surrey, Antimony
Refiner, and JOHN STENHOUSE, of 17, Rodney Street, Pentonville, L.L.D.,
send greeting.
WHEREAS Her, most. Excellent Majesty Queen Victoria, by Her. Letters
Patent, bearing date the Eighth day of January, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto us, the

page_text: said George Hallett and John Stenhouse, Her special licence that we, the
said George Hallett and John Stenhouse, our executors, administrators, and
assigns, or such others as we, the said George Hallett and John Stenhouse,.
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, 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 MANU-
FACTURE OF PIGMENTS FOR COATING SURFACES," upon the condition (amongst
others) that we, the said George Hallett and John Stenhouse, our executors or
administrators, by an instrument in writing under our or their hands and
seals, or under the hand and seal of one of us or them, 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 George Hallett and John Stenhouse
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 :-
Our Invention has for its object improvements in the manufacture of pig-
ments for coating surfaces. For this purpose we employ native oxide of
antimony, or such native oxide of antimony as may contain sulphide of
antimony, which is reduced to a fine powder, the impurities it contains, derived
from its matrix or gangue, are separated by picking and washing as far as
practicable. The finely powdered native oxide of antimony after having been
dried is calcined at a red heat in open vessels or suitable furnaces, with free
access of air till any sulphur present has been expelled, and the oxide has
been converted into or chiefly into antimonious acid. The calcined product
consisting chiefly of antimonious acid is then ground up with suitable oil or
varnish, or other materials, to admit of its being used as a paint. When it is
thought desirable, other oxides, salts, or materials may be combined with the
calcined product consisting chiefly of antimonious acid thus prepared so as to
form pigments suitable for the coating of surfaces.
We likewise employ the native oxide of antimony, or such native oxide of
antimony as may contain sulphide of antimony, and the more or less pure
antimonious acid obtained from them by the process above described for the
manufacture of a yellow pigment. This we produce by taking eight parts of

page_text: either native oxide of antimony, or such native oxide of antimony as may
contain sulphide of antimony or 'antimonious acid more or less pure, three
parts of either red lead or litharge (or two and a half parts of carbonate of
lead) one part of oxide of zinc, and four parts of common salt. These are all
intimately mixed in a state of fine powder, and are then calcined at a red
heat in suitable vessels or furnaces till a combination is effected, and the
yellow pigment is produced. When this has been accomplished, the mass is
reduced to fine powder, and washed with water till all the common salt is
removed. When dried a yellow powder is obtained.
We do not confine ourselves to the quantities of the different materials
above described, but the proportions mentioned are found to answer very well.
Sometimes we increase the quantity of oxide or carbonate of lead, and at
others omit the oxide of zinc altogether, and by varying the proportions of
the ingredients, Naples yellow is obtained of different shades of color.
In carrying out our Invention we employ native oxide of antimony, or such
native oxide of antimony as may contain sulphide of antimony, which native
oxide is found in various localities, where it is usually associated with the
grey sulphide of antimony, from which according to the opinion of minera-
logists it has been produced by the process of oxidation, which as might be
expected is found to be more or less complete. Tbis native oxide of antimony s
whose color varies from light yellow to yellowish red occurs usually massive,
and is by no means very homogenous. It consists of antimony in combination
with oxygen, the amount of which varies, it also generally contains different
quantities of sulphide of antimony, of oxide of iron, of silica, and sometimes
also of arsenic and water. We take the native oxide of antimony, and having
freed it from its gangue as much as is requisite by picking and washing, we
reduce it to fine powder by grinding and sifting. The powdered oxide is
then introduced into large crucibles, muffles, ovens, or suitable furnaces, where
it is cautiously roasted at a low red heat with access of air. It is advisable
to stir the powder occasionally during the roasting with a rake or suitable
ntensil, and to prevent the temperature rising above a low red heat. During
the process of roasting, the powdered ore evolves the vapours of water,
sulphur, and sulphurous acid, together with antimonial and arsenical fumes,
and gradually becomes of a lighter color and less fusible. This process which
usually occupies from two to three hours is known to be completed when no
more sulphurous, antimonial, or arsenical vapours are given off, and the colour
of the powder does not become any lighter or paler. It is then found
that almost all the antimony in the roasted ore is in the state of anhydrous
antimonious acid.

page_text: The impure antimonious acid produced in this way is then reduced to an
almost impalpable powder by grinding and levigating with water. When dried
it constitutes a pigment, and when ground up with suitable quantities of oil or
varnish or other materials it forms a paint. When it is thought desirable other
oxides, salts, or materials, such as oxide of zinc, carbonate of lead, or chromate
of lead may be combined with the calcined product, consisting chiefly of
antimonious acid, thus prepared so as to form pigments suitable for the coating
of surfaces.
.
We likewise employ native oxide of antimony, or such native oxide of
antimony as may contain sulphide of antimony or antimonious acid, more or
Jess pure, or the crude antimonious acid obtained from them by the processes
above described for the manufacture of a yellow pigment. This we produce
by taking eight parts of either native oxide of antimony, or of such native
oxide of antimony as may contain sulphide of antimony or antimonious acid,
more or less pure; or of antimonious acid obtained from them by the process
above described, three parts of either red lead or litharge, and one part of
oxide of zinc. These are all intimately mixed in a state of fine powder, and
are then calcined at a red heat in crucibles, muffles, or other suitable vessels
or furnaces till a combination is effected, and the yellow pigment is produced.
When this has been accomplished, the masses reduced to fine powder, and
when ground up with oil or varnish constitutes a paint. We do not confine
ourselves to the quantities of the different materials above described, but the
Sometimes we
proportions mentioned above are found to answer well.
increase the quantity of oxide of lead, and at others omit the oxide of zinc
altogether. Common salt may also be used in proportion of about four parts,
in which case the calcined product will be washed. By varying the proportion
of the ingredients, as in the subjoined instances, Naples yellow is obtained of
different shades of colour.
1.
Antimonious acid
Oxide of lead
Oxide of zinc
2.
-
4 parts,
-
-
2 parts,
Antimonious acid
Oxide of lead
-
1 part,
- 2 parts,
Oxide of zinc
I part.
-
-
1 part.
-

page_text: In the preceding recipes we have named the employment of antimonious
acid only, because we prefer it, but we likewise employ native oxide of
antimony, or native oxide of antimony containing sulphide or antimonious
acid.
In witness whereof, we, the said George Hallett and John Stenhouse,
have hereunto set our hands and seals, this Fifth day of July, in the
year of our Lord One thousand eight hundred and sixty-one.
GEO. HALLETT.
(L.S.)
JOHN STENHOUSE. (L.S.)
GEO. HALLETT.
(L.S.)
JOHN STENHOUSE. (L.S.)