IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF SULPHIDE OF ZINC
Year: 1879

page_text: LETTERS PATENT to Thomas Griffiths, of Birkenhead, in the County of
Chester, and John Cawley, of Deptford, in the County of Kent, Chemist, for
the Invention of "IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF
SULPHIDE OF ZINC."
Sealed the 2nd September 1879, and dated the 21st March 1879.
PROVISIONAL SPECIFICATION left by the said Thomas Griffiths and John
Cawley at the Office of the Commissioners of Patents on the 21st March
1879.
THOMAS GRIFFITHS, of Birkenhead, in the County of Chester, and JOHN CAWLEY,
of Deptford, in the County of Kent, Chemist. " IMPROVEMENTS IN THE MANU-
FACTURE OR PRODUCTION OF SULPHIDE OF ZINC."
This Invention relates to the production of sulphide of zinc.
In carrying out this Invention we take zinc, either in a metallic state or a
mixture of oxidized compounds of zinc, and carbonaceous matter, which, by the
action of heat, will produce metallic zinc. The zinc is volatilized in any convenient
manner and the vapor passed into a chamber the temperature of which is a little
higher than the boiling point of sulphur. This zinc vapor is met in this chamber
by a current of sulphur vapor in excess of that required to form sulphide of zinc.
The zinc and sulphur combine and form definite sulphide of zinc equivalent to
equivalent. The excess of sulphur causes no deterioration of the product on
account of the high temperature of the chamber in which the vapors meet, but
such excess is passed away to a condenser provided for that purpose, and may be
again utilized,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas Griffiths and John Cawley in the Great Seal Patent
Office on the 20th September 1879.
THOMAS GRIFFITHS, of Birkenhead, in the County of Chester, and JOHN CAWLEY,
"IMPROVEMENTS IN THE MANU-
of Deptford, in the County of Kent, Chemist.
FACTURE OR PRODUCTION OF SULPHIDE OF ZINC."
The said Invention relates to the manufacture or production of sulphide of zinc
to be employed in the manufacture of pigments or for other useful purposes in the
arts.
In carrying out the said Invention the sulphur is melted in a jacket pan heated
preferably by high pressure steam. The melting vessel is connected with a cast
iron still by means of a jacketted pipe, and the connection is regulated by means
of a valve in the bottom of the melting pan. The latter should be at such a height
above the still that the pressure due to the column of sulphur in the conduit pipe
may be greater than the tension of the sulphur vapour in the still, so that when
the valve is opened the sulphur in the melting pans may descend into the still.
The still is kept during the process at a temperature of incipient redness, so that
when the sulphur reaches it the sulphur is immediately vapourised and the resulting
current of vapour passes to the chamber to be hereinafter described.
The zinc is melted in a retort or crucible heated preferably by means of a furnace
on the Siemens or upon a similar principle, and raised to such a temperature that
it begins to volatilize freely. When this takes place the resulting zinc vapour
met by a current of sulphur vapour obtained as above described, and in excess of
that required to form with the zinc sulphide of zinc. The reaction takes place
according to the chemical equation Zn + S Zn S.
The sulphide of zinc is in the form of white extremely light powder which is
carried along by the current of sulphur into the collecting chamber, such as is used
for the manufacture of oxide of zinc. This allows of the separation of the different
constituents of the products into different qualities; those parts that are carried
the farthest are the whitest and best generally. Those portions nearest to the part
of the apparatus where combination takes place may sometimes contain metallic
zinc if the sulphur supply has not been carefully attended to, but this may be
separated from the sulphide by levigation.
The collecting apparatus should be kept at a temperature slightly superior to
that of the boiling point of sulphur in order that sulphur, which is necessarily in
excess, may not be deposited with the sulphide of zinc, but may pass on in the
vapourous form to a suitable condenser where, after condensation, it may be
collected and used again.
Before the sulphur vapour reaches the condenser the last traces of sulphide
carried along with it are collected by the interposition of metallic screens or sieves
placed between the sulphur condenser and the apparatus.
In carrying out the process care must be taken to keep the collecting apparatus
as cool as possible consistently with the fulfilment of the conditions above men-
tioned, viz., that no sulphur be condensed therein. In practice this object can be
effected with little difficulty. Impurities in the zinc and sulphur are of little
consequence provided they are not volatile, and of such a nature that they would
not detract from the whiteness of the sulphide of zinc formed.
The accompanying diagram sectional elevation is given as an example of a plant
that may be employed with good results, but we do not restrict ourselves to the
use of any particular kind of apparatus for carrying out our Invention.
A is the sulphur melting pan with its steam jacket a and steam pipe b; B is a
cast iron still arranged within a gas furnace c; C is a crucible for melting and
volatilizing zinc, the said crucible being contained in a gas furnace d; D is an

page_text: automatic apparatus for freeing the mouth of the zinc vessel from deposited
sulphide of zinc; E is the collecting apparatus, and F the condensing apparatus.
Having now described and particularly ascertained the nature of our said
Invention, and the manner in which the same is or may be used or carried into
effect, we would observe in conclusion that what we consider to be novel and
original, and therefore claim as the Invention secured to us by the hereinbefore in
part recited Letters Patent is,―
The manufacture or production of sulphide of zinc for industrial purposes by
causing the vapour of zinc to be brought in contact with the vapour of sulphur in
order that sulphide of zinc may thereby be produced, substantially in the manner
herein before described.
In witness whereof, I, the said Thomas Griffiths, on behalf of myself and
the said John Cawley, have to this our Specification set my hand and seal,
this Twenty ninth day of August, One thousand eight hundred and seventy
nine
THOMAS GRIFFITHS. (L.S.)