IMPROVEMENTS IN THE MANUFACTURE OF PIGMENTS
Year: 1877

page_text: LETTERS PATENT to Thomas Griffiths, of Liverpool, in the County of Lancaster,
Manufacturer, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
PIGMENTS."
Sealed the 26th March 1878, and dated the 18th October 1877.
PROVISIONAL SPECIFICATION left by the said Thomas Griffiths at the Office
of the Commissioners of Patents on the 18th October 1877.
THOMAS GRIFFITHS, of Liverpool, in the County of Lancaster, Manufacturer.
"IMPROVEMENTS IN THE MANUFACTURE OF PIGMENTS."
This Invention relates to the manufacture of white paints, and consists of an
admixture of native sulphate of baryta with sulphide of zinc, and with or without
the addition of magnesia or carbonate of magnesia.
In carrying out this process I mix native sulphate of baryta and sulphide of
zinc in about equivalent proportions; I prefer to mix them in the moist state, so that
the two ingredients may be thoroughly incorporated together, and I then heat the
admixture to a sufficiently high temperature; or I heat together coal.or other car-
bonaceous matters with the native sulphate of baryta or pass over it coal gas when
at a high temperature, so as to reduce it to sulphide. I then dissolve the said
sulphide, and add to it a solution of sulphate of zinc in equivalent proportions
represented by the formula,-
Zn SO, + Ba S = Ba SO, + Zn S.
The precipitate formed I wash, dry, and heat. In either case I heat out of contact
with atmospheric air, so as to prevent the conversion of the sulphide of zinc into
oxide. This part of my Invention is also applicable to other white paints in which
ulphide of zinc is a constituent

page_text: When the material obtained, according to this Invention, is to be used as a pig-
ment ground in oil I add about 1/4th of its weight of magnesia or carbonate of
magnesia, which causes the oil to saponify, giving the pigment coloring properties
analogous to those of white lead.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Griffiths in the Great Seal Patent Office on the 16th April
1878.
THOMAS GRIFFITHS, of Liverpool, in the County of Lancaster, Manufacturer.
"IMPROVEMENTS IN THE MANUFACTURE OF PIGMENTS."
This Invention relates to the manufacture of white paints, and consists, firstly, of
an admixture of native sulphate of baryta with sulphide of zinc, and with or without
the addition of magnesia or carbonate of magnesia.
In carrying out this process I mix native sulphate of baryta and sulphide of zinc
in about equivalent proportions. I prefer to mix them in the moist state, so that
the two ingredients may be thoroughly incorporated together, and I then heat the
admixture to a sufficiently high temperature, in order that by suddenly cooling the
same increased density may be obtained. Or, I heat together coal or other car-
bonaceous matters with the native sulphate of baryta, or pass over it coal gas at a high
temperature, so as to reduce the sulphate to sulphide. I then dissolve the said
sulphide of barium in water, and by preference I add, at an elevated temperature,
sulphur in a fine state of division, so as to ensure the formation of sulphide of barium,
and I then add to the solution thus resulting a solution of sulphate of zinc in about
equivalent proportions, represented by the formula,—-
Zn SO + Ba S = Ba SO₁ + Zn S.
The precipitate thus formed I wash, dry, and submit the same to an elevated
temperature without access of air. In every case I submit the sulphide of zinc to
an elevated temperature out of contact with atmospheric air, so as to prevent the
conversion of the sulphide of zinc into oxide.
I may mention that hitherto, when sulphide of zinc has been submitted to the
action of an elevated temperature for the production of a pigment or pigments, it
has been customary to submit the same to an elevated temperature in contact with
air.
Now, my Invention differs therefrom in that I submit the sulphide of zinc to an
elevated temperature, taking especial care that air is excluded therefrom, thus
obtaining a uniform product and increasing the density of the pigment, and giving
to it what is technically known as increased body.
Although I have mentioned sulphate of zinc, it will be understood that the
chlorides or other soluble salts of zinc may be employed.
When the material or products obtained according to this Invention are to be
used as pigments they may be ground with oil, and I add thereto about 1/th of their
weight of magnesia or of carbonate of magnesia, which will cause the oil to saponify,
and thus giving the pigment covering properties similar to those possessed by white
lead.

page_text: Having now described and particularly ascertained the nature of my said Inven-
tion, and the manner in which the same is or may be used or carried into effect, I
would observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before in part recited
Letters Patent is, the treatment of precipitated sulphide of zinc by submitting the
same to an elevated temperature without access of air, in order that an improved
product may be obtained, in the manner and for the pusposes herein-before
described.
In witness whereof, I, the said
set my hand and seal, this
hundred and seventy-eight,
Thomas Griffiths, have to this my Specification
Eighth day of April, One thousand eight
THOMAS GRIFFITHS. (L.S.)