MENTS IN THE MANUFACTURE OF SULPHIDE OF ZINC
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I THOMAS MACFARLANE of Montreal in the Province of Quebec and Dominion
of Canada at present residing at Coatbridge in the County of Lanark North
Britain Chemist do hereby declare the nature of my said Invention for IMPROVE-
MENTS IN THE MANUFACTURE OF SULPHIDE OF ZINC" to be as follows:-
I take ordinary Sulphate of Soda or Salt Cake mix it with say half its weight or
thereabouts (it should not be less than 30 per cent) of Bituminous Coal and flux it
in an ordinary reverberatory furnace such as is used for making black Ash. The
newer revolving furnaces can also be used. The mixture fuses at a much lower
temperature and in much less time than ordinary black Ash and is withdrawn
from the furnace as soon as the yellow flames are developed. The resulting Cakes
of black Sulphide of Sodium being porous are easily lixiviated in tanks of the same
description as those used for black ash but they are supplied with steam pipes at
the bottom so that the liquors may be raised to a boiling temperature-When the
lixiviation is thus carried on by means of hot water and the liquors brought up to
a strength of 25° Twaddell a clear yellow Solution is obtained of Sulphide of
Sodium containing also Bisulphide and some Carbonate of Soda but free from iron.
This clear solution is then brought into iron tanks or wooden Vats and mixed with
a solution of of Sulphate or Chloride of Zinc until the mixture possesses a slightly
Acid reaction. At first Sulphide of Zinc hydrate is precipitated mixed with free
Sulphur from the Bisulphide of Sodium and towards the end of the operation Zinc
Carbonate falls down from the action of the Alkaline Carbonate. This mixed
precipitate of free Sulphur hydrated Zinc Sulphide and Zinc Carbonate is separated
by filtration or otherwise from the Supernatant solution dried and ignited at a low
red heat in Gas Retorts or muffle furnaces until the free Sulphur is expelled when
it is at once drawn out of the furnace and into water where it disintegrates and
forms a white pigment of great covering power.
Or I take a solution of Bisulphide of barium or of Calcium prepared by any of
the means or ways known to Chemists or a solution containing polysulphides of
these bases and mix it with a solution of pure Chloride of Zinc and thus produce a
mixture of Hydrated Zinc Sulphide and free Sulphur which I treat in the manner
above described. It is of great importance that the ignition of this mixture should
not be continued longer than is necessary for the expulsion of the free Sulphur
otherwise the pigment becomes yellow and loses its body. The Sulphur in

page_text: subliming and burning forms an atmosphere of itself or of Sulphurous Acid round
the pigment and prevents its oxidation The time for the withdrawal of the charge
from the furnace is indicated by the disappearance of the bluish or yellowish flame
from the burning Sulphur. When it is no longer visible and the charge is
thoroughly mixed it is withdrawn.
Or I take hydrated Sulphide of Zinc prepared by any of the methods known to
Chemists and mix it with from five to ten per cent of Sublimed Sulphur and ignite
the mixture in the manner above described.

page_text: I, THOMAS MACFARLANE of Montreal in the province of Quebec and Dominion
of Canada at present residing at Coatbridge in the County of Lanark North
Britain do hereby declare the nature of my invention for "IMPROVEMENTS IN THE
MANUFACTURE OF SULPHIDE OF ZINC" and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
I take ordinary sulphate of Soda or salt cake and mix it with say about half its
weight or thereabouts (it should not be less than 30 per cent of its weight) of
bituminous Coal and flux it in a suitable furnace such for example as an ordinary
reverberatory furnace or the revolving furnaces used for making black ash The
mixture fuses at a much lower temperature and in much less time than ordinary
black ash and is withdrawn from the furnace as soon as the yellow flames are
developed. The resulting cakes of black sulphide of Sodium being porous are
easily liviviated which may conveniently be effected in tanks of the same
description as those used for black ash but they are supplied with steam pipes
at the bottom so that the liquors may be raised to a boiling temperature When
the lixiviation is thus carried on by. means of hot water and the liquors brought up
to a strength of 25° Twaddell, a clear yellow solution is obtained of sulphide of
Sodium containing also bisulphide and some carbonate of Soda, but free from iron.
This clear solution is then brought into iron tanks or wooden vats or other suitable
vessels and mixed with a solution of sulphate or chloride of zinc until the mixture
possesses a slightly acid reaction. At first sulphide of zinc hydrate is precipitated
mixed with free sulphur from the bisulphide of sodium, and towards the end of the
operation zinc carbonate falls down from the action of the alkaline carbonate.
This mixed precipitate of free sulphur, bydrated zinc sulphide, and zinc carbonate,
is separated by filtration or otherwise from the supernatant solution, dried and
ignited at a low red heat in gas retorts or muffle furnaces, until the free sulphur is
expelled, when the remaining matter is at once drawn out of the furnace and into
water where it disintegrates and forms a white pigment of great covering power.
Or I take a solution of Bisulphide of barium or of Calcium prepared by any of
the means or ways known to chemists, or a solution containing polysulphides of
these bases, and mix it with a solution of pure chloride of zinc and thus produce a
mixture of hydrated zinc sulphide and free sulphur, which I treat in the manner
herein before described. It is of great importance that the ignition of this mixture
should not be continued longer than is necessary for the expulsion of the free
sulphur, otherwise the pigment becomes yellow and loses its body. The sulphur
in subliming and burning, forms an atmosphere of itself or of sulphurous acid
round the pigment and prevents its oxidation. The time for the withdrawal
of the charge from the furnace is indicated by the disappearance of the bluish or
yellowish flame from the burning sulphur. When this is no longer visible and the
charge is thoroughly mixed it is withdrawn.
Or I take hydrated sulphide of zinc prepared by any of the methods known
to chemists, and mix it with from about five to ten per cent of sublimed sulphur,
and ignite the mixture in the manner above described.

page_text: I am aware that it has been proposed to produce sulphide of Sodium by reducing
sulphate of Soda with coal; but the percentage of the latter material used was
small and the resulting cakes were dense and difficult to lixiviate, and the solutions
were always impure and black coloured from dissolved sulphide of iron. I am also
aware that it has been proposed to make sulphide of zinc by mixing solutions of
zinc salts with alkaline or earthy sulphides, but the latter being, unmixed with
bisulphides or polysulphides gave precipitates of zinc sulphide only unmixed with
free sulphur from the ignition of which, yellow coloured pigments resulted.
I desire therefore to state that I do not pretend to a broad claim to the manu-
facture of sodium sulphide or zinc sulphide as so proposed
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed 1 declare that what
I claim is
First As a step in the process of manufacturing sulphide of zinc, the use with
Bulphate of soda or salt cake, of a large percentage of Coal (equal to not less than
thirty per cent of the weight of the sulphate) for producing porous cakes of the
sulphide of sodium as hereinbefore described.
Second As a step in the process of manufacturing sulphide of zinc the pro-
duction of sulphide of sodium solutions free from iron; by lixiviating at a
temperature about 200° Fahrenheit and making strong solutions as herein before
described.
Third In the manufacture of Sulphide of zinc the use of the Bisulphides or
Polysulphides of the metals of the alkalies and alkaline earths for producing
mixtures of hydrated zinc sulphide and free sulphur and igniting the same so
as to obtain pigments of great body and whiteness substantially as herein before
described.
Fourth In the manufacture of Sulphide of zinc the use of an admixture of free
sulphur with hydrated sulphide of zinc, in order to produce while it is being
ignited an artificial atmosphere of Sulphur or sulphurous acid around the same
and so preserve its great body and white colour substantially as hereinbefore
described.