IMPROVEMENTS IN THE MANUFACTURE OF PIGMENTS FOR OIL AND TEMPERA PAINTING
Year: 1881

page_text: LETTERS PATENT to John Bryson Orr, of Cannon Street, in the City of
London, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
PIGMENTS FOR OIL AND TEMPERA PAINTING."
PROVISIONAL SPECIFICATION left by the said John Bryson Orr at the
Office of the Commissioners of Patents on the 25th January 1881.
JOHN BRYSON ORR, of Cannon Street, in the City of London.
IN THE MANUFACTURE OF PIGMENTS FOR OIL AND TEMPERA PAINTING."
"IMPROVEMENTS
In the Specification of a former Patent granted to me, No. 5177, I described a
process for the production of a white pigment by treating solutions of sulphide of
barium with solutions of zinc salts, principally the sulphate, to obtain mixed
precipitates of sulphate of baryta and sulphide of zinc. The production of pigments
by this method has certain attendant disadvantages.
According to my present Invention I am able to produce a much better pigment
at a lower price.
Hitherto the zinc solutions used in the manufacture of pigments have been
obtained from spelter, scrap, or other form of zinc in a metallic state.
I take poor zinciferous ores containing blende or calamine in combination with
other metals, but too poor for or existing in a condition which unfits them for
ordinary metallurgical treatment.
These ores I pulverize to fineness and roast upon the bed of an ordinary
calciner until "sweet." The resulting mass is lixiviated with water to extract all
the zinc existing as sulphate, and thereafter the insoluble portion is treated with
dilute sulphuric acid to exhaust the remaining zinc.
These solutions are mixed together and purified from iron and other impurities
by any of the usual methods.
I next reduce sulphate of barium to the state of sulphide in the usual manner
adopted for the reduction of baryta and lixiviate the mass.
The lixiviated strontic salt is mixed with the purified zinc sulphate, so as to
give ultimately mixed precipitates of strontic sulphate and zincic sulphide corre-
sponding to the equation Sr S + Zn SO₁ = Zn S + Sr SO..

page_text: The precipitates are now collected, dried, calcined at a red heat, cooled, and
washed, and again dried, when they are in the form of a beautifully white powder,
equal to white lead in density and unaffected by sulphurous or other gases.
Strontium being absolutely non-poisonous frees it from an objection urged
against the baryta salts, and being of a density much more nearly approaching
that of the zinc with which it is combined renders the pigment more homogeneous
in character, and consequently more enduring as a paint.
Other proportions of the salts than those before mentioned may be used, and I
sometimes employ the chloride or the nitrate of zinc, but these are more expensive
than the sulphate which I prefer.
I also occasionally use hydrochloric acid for sulphuric in the before mentioned
treatment of the zinciferous ore and obtain solution of zinc chloride therefrom,
which are purified and treated in a similar manner, as described, for the sulphate.
The pigment made by this process is equally suitable for tempera as for oil
painting, and is as easily worked as white wash in the one case or white lead in
the other.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Bryson Orr in the Great Seal Patent Office on the 25th July
1881.
JOHN BRYSON ORR, of Cannon Street, in the City of London.
"IMPROVEMENTS
IN THE MANUFACTURE OF PIGMENTS FOR OIL AND TEMPERA PAINTING."
In the Specification of a former Patent granted to me, No. 517%, I described a
process for the production of a white pigment by treating solutions of sulphide of
barium with solutions of zinc salts, principally the sulphate, to obtain mixed
precipitates of sulphate of baryta and sulphide of zinc.
The production of pigments by this method has certain attendant disadvantages.
According to my present Invention I am able to produce a much better pigment
at a lower price.
Hitherto the zinc solutions used in the manufacture of pigments have been
obtained from spelter, scrap, or other form of zinc in a metallic state.
I take poor zinciferous ores containing blend or calamine in combination with
other metals, but too poor for or existing in a condition which unfits them for
ordinary metallurgical treatment. Common bluestone ore containing from 25 to
30 per cent. of zinc may advantageously be used for the purpose.
These ores I pulverize to fineness and roast upon the bed of an ordinary calciner
until "sweet." The resulting mass is lixiviated with water to extract all the zinc
existing as sulphate and thereafter the insoluble portion is treated with dilute
sulphuric acid to exhaust the remaining zinc. Any copper existing in the ore is
also extracted at the same time.
These solutions are mixed together and the copper is extracted in any well known
way, the solutions are also purified from iron and other impurities by any of the
usual methods.
After the zinc, copper, &c., have been extracted from the ores as above described,
the ores are left in such a state that the lead and other remaining metals can be
obtained by smelting the ore down.
I next reduce sulphate of strontium to the state of sulphide in the usual manner
adopted for the reduction of baryta and lixiviate the mass.
The lixiviated strontic salt is mixed with the purified zinc sulphate so as to give
intimately mixed precipitates of strontic sulphate and zincic sulphide corresponding
to the equation Sr S + Zn SO Zn S+ Sr SO₁.
Various strengths of these liquors may be used, but I prefer to work the strontic
salt at about 1·060 sp. gr. and the zinc at about 1.150 sp. gr.
The precipitates are now collected, dried, calcined at a red heat until all
sulphurous vapours have disappeared, cooled, and washed, and again dried, when
they are in the form of a beautifully white powder equal to white lead in body
and unaffected by sulphurous or other gases.
Strontium being absolutely non poisonous frees it from an objection urged against
the baryta salts, and being of a density much more nearly approaching that of the
zine with which it is combined renders the pigment more homogeneous in character,
and consequently more enduring as a paint. Practically it is difficult to obtain the
strontic salts in a pure state. Čelestine as found has ordinarily combined with it
from 5 to 10 per cent. of the isomorphous barytic salt, but I find that this small
percentage of barytic salt does not materially affect the result.
Other proportions of the salts than those before mentioned may be used, and I
sometimes employ the chloride or the nitrate of zinc before adding sulphate of zinc,
but these are more expensive than the sulphate which I prefer, the result always
being mixed precipitates of zinc sulphide and strontium sulphate.

page_text: I also occasionally substitute hydrochloric acid for sulphuric in the before-
mentioned treatment of the zinciferous ore and obtain solutions of zincic and
cupric chlorides therefrom which are purified and treated in a similar manner as
described for the sulphates.
The pigment made by this process is equally suitable for tempora as for oil
painting, and is as easily worked as white wash in the one case or white lead in
the other.
Having thus described the nature of my Invention and the manner of performing
the same, I would have it understood that I claim,-
First. The production of a white pigment from the precipitate obtained by
treating solutions of sulphide of strontium with solutions of zinc salts, usually the
sulphate.
Second. The production of a white pigment, substantially in the manner herein-
before described.
In witness whereof, I, the said John Bryson Orr, have hereunto set my
hand and seal, this Eighteenth day of July, in the year of our Lord One
thousand eight hundred and eighty one.