IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS SULPHIDE OF ZINC
Year: 1883

page_text: LETTERS PATENT to Edward Hill of Upper Thames Street in the City of
London Merchant for an Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF ANHYDROUS SULPHIDE OF ZINC" communicated to him by Thomas
Macfarlane residing at Montreal Canada Chemist
"
PROVISIONAL SPECIFICATION left by the said Edward Hill at the Office
of the Commissioners of Patents on the 19th October 1883.
EDWARD HILL, of Upper Thames Street in the City of London, Merchant,
IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS SULPHIDE OF ZINC"
a communication to me by Thomas Macfarlane residing at Montreal, Canada,
Chemist,
I take a solution of pure sulphate of zinc and mix it with a solution of any
alkaline hydro-sulphide, thereby forming a precipitate of hydrated zinc sulphide,
which after washing filtering pressing and partial drying I saturate with a
solution of zinc chloride, again dry it, and ignite it in the manner hereinafter to
be described.
Or, I prepare a solution of pure zinc chloride of spec. gravity 1.35 by dissolving
zinc, oxide of zinc, or substances containing the latter in hydrochloric acid, and
mix it with a solution of barium sulphide of specific gravity 1.56 until nearly the
whole, but not all of the zinc is precipitated as sulphide. The latter is then
separated from the supernatant solution by subsidence or filtration, pressed but not
washed, so as to leave in it a small quantity of the undecomposed Chloride of Zinc.
This hydrated sulphide of zinc is ignited in the manner hereinafter to be described.
The solution separated from the precipitate, which contains principally chloride of
barium, is concentrated by evaporation to about one half its original bulk. Strong
sulphuric acid is then added to it in lead lined tanks until a precipitate of sulphate
of baryta is no longer produced. After the latter has subsided, the liquid, which
is a solution of bydrochloric acid, is drawn off and used for preparing fresh
quantities of zinc chloride. The precipitated sulphate of baryta is washed filtered
and sold as "permanent white" or blanc fixe

page_text: Or, I take hydrated sulphide of zinc prepared by any other process than those
described above, either alone or mixed with other substances, and moisten it with
a solution of chloride of zinc, and then dry and ignite it in the manner hereinafter
described.
The hydrated sulphide of zinc either alone or mixed with other substances and
prepared in any of the ways above indicated, and containing more or less chloride
of zinc is exposed on the hearth of a reverberatory or muffle furnace to a red heat,
such heat being equally distributed throughout the charge by constant stirring.
As soon as the charge is dull red throughout and fumes of zinc chloride begin to
be given off the charge is withdrawn from the furnace into water, when it is found
to consist of a soft, white pigment, possessing from three to four times the covering
power or body of white lead as before mentioned. During the operation of
heating, the zinc chloride, as it fuses or volatilises, prevents the access of air to the
sulphide of zinc and preserves it from oxidation.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edward Hill in the Patent Office on the 19th April 1884.
"
EDWARD HILL of Upper Thames Street in the City of London Merchant
"IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS SULPHIDE OF ZINC
a communication to me by Thomas Macfarlane residing at Montreal, Canada,
Chemist
This Invention relates to the manufacture of anhydrous, sulphide of zinc by
treating hydrated sulphide of zinc in the manner hereinafter described
The said Invention has for its object to prevent the oxidation hardening
decoloration and loss of body or covering power which have attended the manu-
facture of anhydrous sulphide of zinc as hitherto conducted-For the purposes of
this Invention the hydrated sulphide of zinc may be prepared by taking a solution
of pure sulphate of zinc and mixing it with a solution of any alkaline hydro
sulphide, thereby forming a precipitate of hydrated zinc sulphide-This precipitate
after washing filtering pressing and partial drying is saturated with a solution of
sinc chloride and is then again dried and is then ignited in the manner hereinafter
described.
Or a solution of pure zinc chloride of a specific gravity of 1.35 may be prepared
by dissolving zinc, oxide of zinc or substances containing the latter in hydrochloric
acid and this is mixed with a solution of barium sulphide of a specific gravity
of 106 until nearly the whole but not all of the zinc is precipitated as sulphide-
The latter is then separated from the supernatant solution by subsidence or
filtration and is pressed but not washed so as to leave in it a small quantity of the
undecomposed chloride of zinc-This hydrated sulphide of zinc is ignited in the
manner hereinafter described-The solution separated from the precipitate which
contains principally chloride of barium may be utilized by being concentrated by
evaporation to about one half its original bulk-Strong sulphuric acid is then
added to it in lead lined tanks until a precipitate of sulphate of baryta is no longer
produced After the latter has subsided, the liquid which is a solution of hydro-
chloric acid is drawn off and may be used for preparing fresh quantities of zinc
chloride-The precipitated sulphate of baryta may be washed filtered and sold as
permanent white or blanc fixé.
**
Hydrated sulphide of zinc prepared by any other process than those described
above may however be used for the purposes of this Invention (either alone or
mixed with other substances) it being moistened with a solution of chloride of
zinc and then dried and ignited in the manner hereinafter described.
The hydrated sulphide of zinc (either alone or mixed with other substances)
containing more or less chloride of zinc is exposed on the hearth of a reverberatory
or muffle furnace to a red heat such heat being caused to be equally distributed
throughout the charge which may be effected by constant stirring-As soon as the
charge has attained a dull red heat throughout and fumes of zinc chloride begin to
be given off, the charge is withdrawn from the furnace into water when it is found
to consist of a soft white pigment possessing from three to four times the covering
power or body of white lead as before mentioned-During the operation of heating
as hereinbefore mentioned the zinc chloride as it fuses or volatilises prevents the
access of air to the sulphide of zinc and preserves it from oxidation and consequent
hardening decoloration and loss of covering power.
I am aware that it has been proposed to produce sulphide of zinc for use as a
pigment by processes in some respects resembling those above described but great
difficulty has been experienced in igniting the sulphide without oxidizing and

page_text: hardening it, and causing discoloration and loss of body-I do not claim as the
present Invention the production of hydrated sulphide of zinc by the processes
above described but what I claim as secured to me by the herein before in part
recited Letters Patent is.
The manufacture of anhydrous sulphide of zinc by heating bydrated sulphide
of zinc in the presence of chloride of zinc in the manner and for the purpose
hereinbefore described.
In witness whereof I the said Edward Hill have to this my Specification set my
hand and seal this first day of April One thousand eight hundred and eighty four.
Witnessed
April 1/81
HUGH HILL
25/27 Cedar St
(4.8)