Improvement in the Manufacture of Paints and Pigments.
Year: 1895

page_text: Date of Application, 23rd July, 1895
Complete Specification Left, 23rd May, 1896-Accepted, 18th July, 1896
PROVISIONAL SPECIFICATION.
Improvement in the Manufacture of Paints and Pigments.
SAMUEL BARNETT SCHRYVER, 11 Taviton Street, Gordon Square, in the
County of Middlesex, Demonstrator of Chemistry at University College,
Liverpool, do hereby declare the nature of this invention to be as follows:-
The formation of a paint or pigment, consisting essentially of a mixture of
tersulphide of arsenic & sulphur, the said paint being precipitated by the addition
of an acid, preferably hydrochloric acid to a mixture of a solution of sulphur in
lime (the proportions being such that pentasulphide of calcium is formed), and a
dilute solution of white arsenic in an alkali (such a solution containing therefore
the arsenite of an alkali metal, or alkaline earth). Such a paint can be precipitated
together with other pigments such as Prussian blue.
Dated this 22nd day of July 1895.
I SAMUEL BARNETT SCHRYVER of 11 Taviton Street Gordon Square in the
County of Middlesex Demonstrator of Chemistry at University College Liverpool
do hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
The object of the invention is the manufacture of a pigment consisting essentially
of tersulphide of arsenic and sulphur the said paint being precipitated by the
addition of an acid preferably hydrochloric acid to a mixture of a solution of
sulphur in lime (the proportions being such that pentasulphide of calcium is
formed) and a dilute solution of white arsenic in an alkali such a solution containing
therefore the arsenite of an alkali or alkaline earth. It is not necessary however
to form the two solutions separately and subsequently mix them together before
adding the acid as the solution of sulphur in lime may be first formed and the
arsenic added thereto.
As an example of the latter method which is the more convenient in practice the
following may be quoted.
56 lbs. of quick lime are slaked and 100 gallons of water added. 160 lbs. of
flowers of sulphur are then added thereto and the mixture is then boiled in wooden
vats by wet steam until the liquid becomes nearly clear: the solution then has
a dark brown almost red colour and is decanted from the sediment and run into
another wooden vat.
198 lbs. of white arsenic are then added to the clear solution and the mixture
is then boiled by wet steam. The arsenic gradually dissolves with the separation
of part of the sulphur as a fine white precipitate. The boiling is continued and
gradually a bright yellow pigment separates out. The steam is passed through
the vat until the pigment reaches its maximum of brightness. The whole is

page_text: then allowed to cool and crude hydrochloric acid is then added until the liquid
in the vat has a faint acid reaction, the mixture being kept continually stirred
during the addition. The precipitated pigment is theu filtered off, washed with
water and dried at as low a temperature as possible.
If the solutions be formed separately and then mixed the boiling will be used
both for the formation of the solutions and for the mixed solutions as will be
readily understood.
In the above method a mixture of thio-sulphate of calcium and polysulphide
of calcium (obtained by the action of lime on sulphur) is first formed. On heating
such a mixture with white arsenic a double decomposition takes place, the
sulphur of the thio-sulphate and of the poly-sulphide replacing the oxygen of
the white. arsenic thus forming a sulphide of arsenic, and at the same time a
certain amount of free sulphur is deposited and by working with the proportions
as stated above a body is obtained corresponding by analysis nearly with the
chemical formula AS,S,.
It is not absolutely essential to have as much as 160 lbs. of sulphur present, but
under any circumstances the sulphur must not be in smaller quantities than
96 lbs., the proportions of the other bodies being kept as above. It can be mixed
with blue pigments such as Prussian blue to give green, the amount of Prussian
blue being varied according to the shade of green required. The pigments thus
prepared are well adapted for the manufacture of certain enamel paints and are
specially valuable (owing to the quality of the sulphide of arsenic as an anti-
fouling substance) for covering or protecting iron, metal, wood, and surfaces
generally exposed to the action of water, and especially the bottoms of ships,
in order to prevent the adherence of weeds barnacles and other like matters
thereto. For this purpose the pigment requires only to be mixed with materials
such as are ordinarily used as a basis in forming compositions for covering such
exposed surfaces. For instance 2 cwt. of the pigment added to a composition
consisting of 3 cwt. of oxide of iron, 3 cwt. of resin, 1 cwt. of oxide of zinc, 28 lbs. of
deodorized lime, 70 gallons of boiled oil and 180 gallons of deodorized benzoline
will give a composition possessing the necessary antifouling quality.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
a. The above described process for the manufacture of a substance suitable for
paint or antifouling compositions.
b. The application of the substance so produced to the formation of paints and
anti-fouling compositions.
Dated this 22nd day of May One thousand eight hundred and ninety-six.
SAMUEL BARNETT SCHRYVER.