A NEW AND IMPROVED PROCESS FOR PRODUCING A FIXED WHITE PIGMENT FOR PAINTING AND DISTEMPERING PURPOSES
Year: 1882

page_text: LETTERS PATENT to Henry Knight, of Liverpool, in the County of Lancaster,
Paint Manufacturer, for an Invention of "A NEW AND IMPROVED PROCESS
FOR PRODUCING A FIXED WHITE PIGMENT FOR PAINTING AND DISTEMPERING
PURPOSES,"
PROVISIONAL SPECIFICATION left by the said Henry Knight at the Office
of the Commissioners of Patents on the 18th February 1882.
HENRY KNIGHT of Liverpool in the County of Lancaster, Paint Manufacturer.
"A NEW AND IMPROVED PROCESS FOR PRODUCING A FIXED WHITE PIGMENT FOR
PAINTING AND DISTEMPERING PURPOSES."
The object of this invention is to produce a pure white pigment, suitable for
painting in oil or in water, fast in colour, unaffected by sulphuretted hydrogen or
other gases, and not darkened by action of the sun's rays thereon.
In carrying my said invention into practice, I proceed as follows:-No. 1-
I take sulphide of soda, made by any of the ordinary methods, or by dissolving
three parts, by weight of caustic soda with one part, by weight, of sulphur, or
thereabouts.
No. 2 Sulphate of zinc, made either by roasting sine-blende (Zn S, the sulphuret
of zinc); or by dissolving 112 parts, by weight, of metallic zine in 172 parta, by
weight, of sulphuric acid, adding thereto such proportion of water as may be found
requisite. Or I may use the chloride in place of the sulphate of zinc, or a mixture
of chloride and sulphate of zinc.
No. 8-Chloride of strontia, made by any of the usual methods, or by dissolving
20 parts, by weight, of carbonate of strontia in 24 parts, by weight, of
bydrochloric acid (more or less), adding thereto such proportion of water as may be
found requisite.
Any impurities, in the said chemical compounds, may be removed by any
suitable and efficient means.

page_text: Total
I first mix Nos. 1 and 2 together and then add the No. 3. Or I may first mix
Nos. 2 and three together and then add No. 1. The proportions of the said parts
may be varied for producing different qualities of my improved pigment. The
resulting precipitate is then filtered and dried upon an ordinary drying kiln, or
otherwise.
As the said dried precipitate contains chloride of sodium, it may be calcined at a
high temperature without danger of the zinc turning yellow, as it would do if so
calcined without the protection of such chloride.
The said calcined precipitate is then levigated, washed, and dried, when it is
ready for use.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Knight in the Great Seal Patent Office on the 18th August
1882.
HENRY KNIGHT of Liverpool in the County of Lancaster, Paint Manufacturer.
" A NEW AND IMPROVED PROCESS FOR PRODUCING A FIXED WHITE PIGMENT FOR
PAINTING AND DISTEMPERING PURPOSES,
"
The object of this invention is to produce a pure white pigment, suitable for
painting, in oil or in water, fast in color, unaffected by sulphuretted hydrogen or
other gases, and not darkened by action of the sun's rays thereon.
In carrying my
All the parts of the materials named herein are parts by weight..
said invention into practice, I proceed as follows:-
No. 1 compound-I take sulphide of soda, made by any of the ordinary
methods, or by dissolving three parts of caustic soda with one part of sulphur, or
thereabouts.
No. 2 compound-I take sulphate of zinc, made either by roasting zinc-blende
(Zns, the sulphuret of zinc), or by dissolving 112 parts of metallic zinc in 172 parts
of sulphuric acid, adding thereto such proportion of water as may be found requisite.
Or I use the chloride in place of the sulphate of zinc, or a mixture of chloride and
sulphate of zina.
No. 3 compound-I take chloride of strontium, made by any of the usual
methods, or by dissolving 20 parts of carbonate of strontia in 24 parts of
hydrochloric acid (more or less); adding thereto such proportion of water as may
be found requisite. Or I use a mixture of carbonate and sulphide or chloride of
strontium.
Any impurities in the said three chemical compounds, may be removed by any
suitable and efficient means.
I then first mix together about equal parts of Nos, 1 and 2 thus forming sulphide
of zinc and sulphate of soda; and then add thereto another such equal part of the
No. 8; when sulphate of strontia is thereby formed, and chloride of sodium remains
in solution. Fifty per cent. of this solution remains in the pigment after pressing.
Or I may first mix Nos. 2 and 3 together, and then add the No. 1; which gives the
same result.
This compound is then precipitated, and the precipitate filtered and then dried
upon an ordinary drying kiln, or otherwise.
As the said compound contains chloride of sodium, it may be calcined at a high
temperature without any fear of the zinc turning yellow, as it would do if calcined
at a similar temperature without such protection
This calcined precipitate is then levigated, washed and dried, and is then fit for
use as a pigment in oil for painting, or in water for distempering.
For producing a cheaper pigment of the same character, I take sulphide of
strontia, and add thereto about an equal quantity of sulphate of soda. The
precipitate formed from these ingredients is composed of sulphate of strontia and
sulphide of soda chemically combined. I then add chloride of zinc thereto gradually,

page_text: as long as any precipitate is formed; such precipitate being sulphide of zinc and
chloride of sodium. By this process, I produce a fixed white pigment, which is not
discolored by calcination.
The proportion of the chloride of zinc used may be an equal part, or be a little
more or less according to the quality of pigment required.
Having thus fully described and ascertained the nature of my said invention,
and the method of performing the same, I desire it to be understood that I do not
restrict myself to the precise number of parts herein stated for making the said
compound, as they may be somewhat varied, for producing different qualities of my
improved pigment, without departing from the main characteristics of the
invention but I claim as new and desire to secure by the hereinbefore mentioned
in part recited Letters Patent:-
Firstly The use of carbonate of strontia or chloride of strontium in combination
with salts of zinc and sulphide of soda, for producing a pure white pigment for
painting or distempering.
Secondly The use of sulphide of strontia, in combination with sulphate of soda
and chloride of zinc, for producing a fixed white pigment, which is not discolored
by calcination.
Thirdly The production and application of chloride of sodium, as a protective
Agent against the discoloration of the said pure or fixed white pigment during its
calcination.
In witness whereof I, the said Henry Knight, have hereunto set my hand
and seal this sixteenth day of August in the year of our Lord one thousand
eight hundred and eighty-two.