Improvements in and connected with the Obtainment of Cyanides and Ferrocyanides.
Year: 1890

page_text: ate of Application, 19th May, 1890
Complete Specification Left, 17th Feb., 1891-Accepted, 21st Mar., 1891
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Obtainment of Cyanides
and Ferrocyanides.
I, DAVID JAMES PLAYFAIR, of 12, Woodside Terrace, Glasgow, in the
County of Lanark, North Britain, Manufacturing Chemist, do hereby declare
the nature of this invention to be as follows, that is to say :-
My said invention has for its object the obtainment of cyanides, and ferro-
cyanides in an improved and economical manner. I obtain the cyanides and
ferrocyanides from sulphocyanates or from bisulphide of carbon and ammonia
and I reconvert the bye products.
In carrying out the invention according to one modification, I form sulpho-
cyanate of potash, or of soda, or of an alkaline earth, by treating sulphocyanate
of ammonia with the hydrate or carbonate of the alkali or earth. This sulpho-
cyanate I mix with ground wood charcoal or other suitable carbon, and with a
metal such as lead or zinc having a strong affinity for sulphur and forming an
insoluble sulphide such metal being in a state of fine division. I heat the mixture
in a retort obtaining thereby sulphide of the metal and cyanide of the alkali
or earth.
After cooling the cyanide is separated from the insoluble sulphide by lixiviation,
and may be obtained in the solid form by evaporation. The metallic sulphide is
roasted, reduced to the metallic form, and used over again.
66
If ferrocyanides are required there is added to the mixture to be heated in the
retort, iron which may be in the form of scrap, turnings, borings or filings.
The sulphocyanate of ammonia employed may be obtained from " gas liquor" or
gas lime
or in any other convenient way; but I prefer to obtain it by heating
together in a closed vessel liquid ammonia and bisulphide of carbon; or by-mixing
in a common condenser or other suitable vessel the vapors of ammonia and
bisulphide of carbon, or by passing the vapor of one into the other in a liquid state.
The resulting solution of sulphocyanate of ammonia is heated in a still to drive off
any free ammonia and sulphide of ammonium, which are collected in suitable
condensers or absorbers for further use in the process. The solution of sulpho-
cyanate of ammonia, is next separated from precipitated sulphur by settling and
decanting or filtering, and is treated as herein before described to obtain cyanides or
ferro cyanides. The ammonia separated in forming the sulphocyanate of an alkali
or earth is collected and used over again.
Dated this Seventeenth day of May 1890.
EDMUND HUNT,
Applicant's Agent.
COMPLETE SPECIFICATION.
Improvements in and connected with the Obtainment of Cyanides
and Ferrocyanides.
I, DAVID JAMES PLAYFAIR, of 12, Woodside Terrace, Glasgow, in the
County of Lanark, North Britain, Manufacturing Chemist, 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,
that is to say :-
My said invention has for its object the obtainment of cyanides, and ferro-
cyanides in an improved and economical manner. I obtain the cyanides and

page_text: ferroycanides from sulphocyanates or from bisulphide of carbon and ammonia, and
I reconvert or utilise the bye products.
In carrying out my invention I obtain cyanides by heating together in a retort
or crucible the sulphocyanate of an alkali or alkaline earth with lead or zine or a
mixture thereof, these metals having a strong affinity for sulphur and forming
insoluble sulphides. Ground wood charcoal or other suitable carbon may be mixed
with the charge of sulphocyanate and lead or zinc, or may be merely spread over so
as to cover the top of the charge, or it may be dispensed with altogether. The
carbon is not essential and takes no part in the reaction between the metal and the
sulphocyanate, its function being merely to maintain a reducing temperature within
the retort or crucible, to prevent oxidation of the cyanide formed to cyanate,
and to reduce to cyanide any cyanate accidentally formed by access of air to
the charge or in consequence of any oxygen compounds of the lead or zinc
being present.
The lead or zinc may, in a state of fine division produced by granulation or
other mechanical means, be thoroughly incorporated with an equivalent weight
of the dry alkaline sulphocyanate, so as to produce an intimate mixture before
being charged into the crucible or retort; or the materials may be put into the
retort or crucible in any convenient form and be sufficiently mixed by stirring
when they have reached a state of fusion.
The charge is heated to a temperature somewhat above the melting point of zine,
whereupon a reaction takes place resulting, when sulphocyanate of sodium is used
in the production of cyanide of sodium and sulphide of zinc. When zinc is used
the reaction which proceeds slowly at first, subsequently becomes violent and stops
suddenly on completion; and the charge must then be withdrawn from the retort or
cruicble or the latter be removed from the source of heat. Otherwise on pro-
longing the heating, another reaction supervenes, producing undesirable results.
When lead is used the reaction is much less violent; and the fused mass of
alkaline cyanide and lead sulphide may be allowed to settle and some of the cyanide
be poured off. Some cyanide however remains in contact with the lead sulphide
and must be separated from it by solution.
When zinc has been used no settling of the fused mass is practicable, and the
cyanide must be separated by lixiviation after the materials have become cool.
When the fusing operation has been carefully performed the resulting solution of
alkaline cyanide will be found practically free from sulphide. If however any
sulphide is present it may be removed by agitating the solution after adding a
suitable quantity of freshly precipitated cyanide of lead which may be formed by
adding to a small quantity of the solution a solution of chloride or other soluble salt
of lead. The sulphur will be precipitated as sulphide of lead which after settling
may be separated by decantation and filtering.
The solution of alkaline cyanide may be used for many technical purposes without
further treatment, or it may be evaporated to dryness, the evaporation being by
preference effected in a vacuum pan to avoid decomposition of the cyanide.
When lead is used in the process the resulting sulphide of lead may be roasted
and reduced to the metallic state to be used over again.
When zinc is used, the resulting sulphide of zinc, may be reconverted like the
lead, or it may be applied as a pigment after or without being roasted, or it may be
dissolved in acid for the production of salts of zinc, sulphuretted hydrogen being at
the same time formed and available for the production of sulphur by known means.
When ferro-cyanides are required I modify the process herein before described
by replacing part of the lead or zinc with iron, in the form of borings, turnings, or
other porous form. In the fusing process the iron is converted into sulphide along
with the lead or zinc, but on subsequent lixiviation reacts with the alkaline cyanide
forming a ferrocyanide of the alkali which may be crystallised.
The sulphocyanates employed may be obtained from the sulphocyanate of
ammonia met with in “ gas liquor" or "
or obtained from any other
gas lime"
I however prefer to obtain the sulphocyanate by heating
convenient source.

page_text: together in a closed vessel liquid ammonia and bisulphide of carbon along with a
solution of a fixed alkali or alkaline earth (preferably as a hydrate, although either
a carbonate or a sulphide may be used) or by mixing in a condenser or other suitable
vessel the vapors of ammonia and bisulphide of carbon, or by passing the vapor of
one into the other in a liquid state, and adding a solution of the fixed alkali.
The resulting solution is heated in a still to drive off any free ammonia and
sulphide of ammonia and any other ammoniacal compounds that may be present,
the products so volatilised being collected in condensers or absorbers for further
use. The solution of sulphocyanate of the fixed alkali remaining in the still is
separated from precipitated sulphur by settling, decanting, and filtering; and is
then evaporated to dryness and treated as hereinbefore described to obtain cyanides
and ferrocyanides.
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 :-
1. The process for obtaining cyanides by fusing a sulphocyanate of a fixed alkali
or alkaline earth with lead or zinc or a mixture thereof and subsequently separating
the metallic sulphide formed, substantially as hereinbefore described.
2. The process for obtaining ferro-cyanides by fusing a sulphocyanate of a fixed
alkali or alkaline earth with lead or zinc in the presence of iron, subsequently
lixiviating the mass and crystallising the ferrocyanide substantially as hereinbefore
described.
3. In combination with either of the processes claimed in the first and second
claims, forming the sulphocyanate employed in any of the modes hereinbefore
described and reconverting or utilising the metallic sulphides, substantially as
hereinbefore described.
Dated this Sixteenth day of February 1891.
EDMUND HUNT,
Applicant's Agent.