IMPROVEMENTS IN PIGMENTS CONTAINING ZINC COMPOUNDS, AND IN THE MANUFACTURE THEREOF
Year: 1884

page_text: COMPLETE SPECIFICATION.
I, HENRY KNIGHT, at the Office for Patents, 6 Lord Street, Liverpool, in the
County of Lancaster, Paint Manufacturer, do hereby declare the nature of my said
Invention for "IMPROVEMENTS IN PIGMENTS CONTAINING ZINC COMPOUNDS, AND
IN THE MANUFACTURE THEREOF," and in what manner the same is to bo
performed, to be particularly described and ascertained in and by the following
statement:-
This improved pigment consists of an intimate mixture of sulphide and oxide of
zinc with or without other mineral matter, such as sulphate of barium, or oxide of
magnesium. One object of using oxide with the sulphide is to improve the color
and prevent that peculiar darkening tendency that sulphide alone or sulphide of
zinc and sulphate of barium precipitated together are apt to have. A pigment has
for some time been manufactured from a mixed precipitate of sulphide of zinc and
sulphate of barium, of which the sulphate of barium forms nearly two thirds by
weight; such a precipitate is liable to become more or less discoloured in the process
of calcination to which it is subjected in order to give it body, and the large
quantity of sulphate of barium present is unsatisfactory since this salt possesses no
body in itself and has but little absorptive power for oil.
The object of using oxide of zinc with the sulphide is to produce a pigment
consisting wholly or in greater part of these two zinc compounds, by which a
pigment is secured of superior quality in every respect to that hitherto made, and
to improve the color by preventing or rendering inappreciable the discoloration to
which sulphide of zinc is liable during calcination. In calcining sulphide of zinc
with more or less access of air some of the sulphide may be oxidised, into an
oxysulphide, but any such compound is inferior in colour and body and forms but a
very small proportion of the calcined precipitate.
Now by my Invention I secure the benefits of a large addition of oxide of zinc
without any loss of body by oxidising the sulphide, and it consists in adding
ordinary oxide of zinc to precipitated sulphide of zinc or a mixed precipitate of
sulphide of zinc and sulphate of barium previous to the calcination, and calcining
preferably out of contact of air (so as to prevent the oxidation of the sulphide) at
a degree of heat below that at which the oxide volatizes, or I add dry oxide of zinc
to the calcined or uncalcined sulphide of zinc or mixed precipitate of sulphide of
מ.

page_text: zinc and sulphate of barium and grind them together, thereby forming an intimate
mixture of sulphide and oxide of zinc, or of sulphide of zinc, oxide of zinc and
sulphate of barium and not an oxysulphide such as may be formed in small
quantity in the ordinary process. To this before or after grinding, but preferably
before, I sometimes add a little magnesia. The proportions I have found best in
practice are from two to three parts by weight of oxide of zinc to one of pure
sulphide of zinc, or one part by weight of oxide of zinc to from one to two of the
mixed precipitate of sulphide of zinc and sulphate of barium, thus producing a
pigment consisting wholly or in greater part of sulphide and oxide of zinc.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
1 claim is :-
1 A pigment formed of sulphide of zinc and oxide of zinc in intimato
mechanical mixture with or without other ingredients, substantially as described.
2nd The method of forming an intimate mechanical mixture of sulphide of zine
and oxide of zinc composed of true oxide and true sulphide, (not oxysulphide)
with or without other ingredients such as sulphate of barium or oxide of
magnesium, substantially as described.
W. P. THOMPSON & Co.,
Dated this 4th day of Annil 100