Improvements in Obtaining Cyanides from Residuary Liquors Formed in Chemical Processes.
Year: 1889

page_text: Date of Application, 21st Feb., 1889
Complete Specification Left, 20th Nov., 1889-Accepted, 21st Dec., 1889
PROVISIONAL SPECIFICATION.
Improvements in Obtaining Cyanides from Residuary Liquors
Formed in Chemical Processes.
I. JOHN STEWART MACARTHUR, Analytical and Technical Chemist, of 15 Princes
Street, Pollokshields, in the County of Renfrew, North Britain, do hereby declare the
nature of this invention to be as follows:-
This Invention has for its object the economical treatment of residuary liquors
formed in chemical, processes in which cyanides have been used as active agents, in
order to obtain cyanides suitable for being used again.
In carrying out the Invention the residuary liquor to be treated may be taken in
an alkaline or neutral condition. Such liquor may contain in solution one or mora
of the following chemicals, namely, simple cyanides such as those of the alkalies or
the alkaline earths, compound cyanides such as ferrocyanides, or ferricyanides or
double cyanides such as those of zinc or other metals with alkalies.
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When the liquor contains much zinc and a compound cyanide most of the zine
should be removed at the outset by adding a solution of a sulphide, excess thereof
being avoided. After separating the liquor from a precipitate which is formed and
which contains the zinc, the liquor is run into stills, and there is added to it sufficient
acid (preferably sulphuric acid or an equivalent acid salt such as bisulphate of soda)
to render the liquor neutral. Or if found preferable alkalinity due to soluble car-
bonates may be neutralised before running the liquor into into the stills, by adding
chloride of calcium, the carbonate of calcium formed being removed along with or
separately from the precipitate containing zinc.
To the neutral liquor in the still there is next added sufficient acid, somewhat in
excess of that theoretically required, to liberate all the cyanogen of the simple and
double cyanides, and half the cyanogen of the compound cyanides, in the form of
hydrocyanic acid, on the application of heat. Heat is applied to the still, either
externally, or by an internal steam pipe, or by injecting steam; and the hydro-
cyanic acid volatilised is passed through suitable condensing apparatus, and is
absorbed by caustic alkaline solutions, the desired simple soluble cyanides being
thereby obtained. The solution obtained may be evaporated if desired; or the hydro-
cyanic acid may be absorbed by hydrates in the dry state.
When hydrocyanic acid ceases to come from the still, if compound cyanides have
been present, there will remain in the still along with the liquid, which will now be
free or nearly so from hydrocyanic acid, ansinsoluble compound containing about half
the cyanogen of the compound cyanides originally in the liquor. The insoluble
matter is separated as a sludge and is treated with an alkaline hydrate in solution or
with milk of lime in quantity a little more than enough to neutralise the acidity of
the sludge, and to decompose the sludge. Half of the iron or other metal is replaced
by the metal of the alkali or the alkaline carth, the iron being separated as hydrate,
whilst all the remaining cyanogen is again brought into solution as a soluble compound
cyanide. This solution after separation from the insoluble hydrate may be mixed
with a fresh charge of the original liquor or be treated in the same manner, or it may
be evaporated to yield crystalised salts.
When the original liquor contains only a small proportion of cyanogen com-
pounds, it may be convenient to concentrate them, which can be effected by adding
solutions of salts such as those of iron, and slightly acidifying. The whole of
the cyanogen is thereby brought down as an insoluble compound cyanide which
may be treated as hereinbefore described with reference to the sludge from the
still.

page_text: The substances freed from cyanogen by the processes hereinbefore described or
some of them may be made into useful products by well known means.
The apparatus used in carrying out the Invention comprises stills, condensers, and
receivers. The stills, when steam heat is to be used, may be of wood lined or not
lined with lead or other suitable material not materially acted on by the acid
liquors or they may be glass, earthenware or other inert material.
When heat
is applied externally the stills may be of iron lined with lead or other suitable
material. The condensers should be made of or lined with lead or other material
not materially acted on by the vapours or liquids. The receivers, which should be
gas-tight may be of wood or other suitable material not materially acted on by
The vapours and liquids. A number of receivers may be used being arranged in a
rotation series, or any other suitable arrangement may be adopted.
When dry
hydrates are used to absorb the hydrocyanic acid they may be placed on shelves
in a gas-tight box or chamber of wood or other suitable material, the chamber
having as exit a leaden or other suitable pipe dipping into a vessel containing a
solution of an alkaline bydrate to catch the last traces of hydrocyanic acid.
Dated this 21st day of February 1889.
ALLISON BRUS.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Obtaining Cyanides from Residuary Liquors
Formed in Chemical Processes.
I, JOHN STEWART MACARTHUR, Analytical and Technical Chemist, of 15 Princes
Street, Pollokshields, in the County of Renfrew, North Britain, 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:-
This Invention has for its object the economical treatment of residuary liquors
formed in chemical processes in which cyanides have been used as active agents,
in order to obtain cyanides suitable for being used again.
In carrying out the Invention the residuary liquor to be treated may be taken in
an alkaline or neutral condition. Such liquor may contain in solution one or more
of the following chemicals, namely, simple cyanides such as those of the alkalies or
the alkaline earths, compound cyanides such as ferrocyanides, or ferricyanides or
double cyanides such as those of zinc or other metals with alkalies.
When the liquor contains much zinc and a compound cyanide most of the zinc
should be removed at the outset by adding a solution of a sulphide, excess thereof
being avoided. The addition of the sulphide besides precipitating the zinc will
regenerate alkaline cyanide from any cyanide of zinc that may be present.
After separating the liquor from a precipitate which is formed and which contains
the zinc, the liquor is run into stills, and there is added to it sufficient acid (preferably
sulphuric acid or an equivalent acid salt such as bisulphate of soda) to render the
liquor neutral. Or if found preferable alkalinity due to soluble carbonates may be
neutralized before running the liquor into the stills, by adding chloride of calcium,
the carbonate of calcium formed being removed along with or separately from the
precipitate containing zinc.
To the neutral liquor in the still there next added sufficient acid, somewhat in
excess of that theoretically required, to liberate all the cyanogen of the simple and
double cyanides, and half the cyanogen of the compound cyanides in the form of
hydrocyanic acid on the application of heat. Heat is applied to the still, either
externally, or by an internal steam pipe, or by injecting steam; and the hydro-
cyanic acid volatilized is passed through suitable condensing apparatus, and is absorbed
by caustic alkaline solutions, the desired simple soluble cyanides being thereby obtained.
The solution obtained may be evaporated if desired; or the hydrocyanic acid may be
absorbed by hydrates in the dry state.

page_text: Previous to or during the distillation air may be caused to pass through the liquor
in the still, and will thereby assist the action.
When hydrocyanic acid ceases to come from the still, if compound cyanides have
been present, there will remain in the still along with the liquid, which will now be
free or nearly so from hydrocyanic acid, an insoluble compound containing about half
the cyanogen of the compound cyanides originally in the liquor. The insoluble
matter is separated as a sludge and is treated with an alkaline hydrate in solution or
with milk of lime in quantity a little more than enough to neutralize the acidity of
the sludge, and to decompose the sludge. Half of the iron or other metal is
replaced by the metal of the alkali or the alkaline earth, the iron being separated as
hydrate, whilst all the remaining cyanogen is again brought into solution as a soluble
compound cyanide, the reaction being greatly accelerated by heat. This solution
after separation from the insoluble hydrate may be mixed with a fresh charge of the
original liquor or be treated in the same manner; or it may be evaporated to yield
crystallized salts.
it
When the original liquor contains only a small proportion of cyanogen compounds,
may be convenient to concentrate then, which can be effected by adding solutions
of salts such as those of iron, and slightly acidifying. The whole of the cyanogen
is thereby brought down as an insoluble compound cyanide which may be treated as
hereinbefore described with reference to the sludge from the still.
The substances freed from cyanogen by the processes hereinbefore described or some
of them may be made into useful products by well known means.
The apparatus used in carrying out the Invention comprises stills, condensers, and
receivers. The stills, when steam heat is to be used, may be of wood, lined or not
lined with lead or other suitable material not materially acted on by the acid liquors;
or they may be glass, earthenware, or other inert material. When heat is applied
externally the stills may be of iron lined with lead or other suitable material. The
condensers should be made of or lined with lead or other material not materially
acted on by the vapors or liquids. The receivers, which should be gas-tight, may be
of wood or other suitable material not materially acted on by the vapors or liquids.
A number of receivers may be used being arranged in a rotation series, or any other
suitable arrangement may be adopted. When dry hydrates are used to absorb the
hydrocyanic acid they may be placed on shelves in a gas-tight box or chamber of wood
or other suitable material, the chamber having as exit a leaden or other suitable pipe
dipping into a vessel containing a solution of an alkaline hydrate to catch the last
traces of hydrocyanic acid.
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. In processes for obtaining cyanides from residuary liquors containing also zinc,
first separating all or a large portion of the zine by precipitation with a sulphide,
substantially as hereinbefore described.
2. Treating insoluble compound cyanides, present after distilling off the free
hydrocyanic acid, by decomposing them with an alkaline hydrate or with milk of
lime, substantially as and for the purposes herein before described.
3. Obtaining concentrated solutions of cyanogen compounds from residuary liquors
containing small quantities thereof, by precipitation with salts of iron or other
suitable salts, thereby forming insoluble compound cyanides, and by subsequent
decomposition of the separated precipitates with an alkaline hydrate or with milk of
lime, substantially as and for the purposes hereinbefore described.
4. The combination of processes for obtaining cyanides from residuary liquors, and
comprising the precipitation of zinc with a sulphide, the acidifying of the liquor and
distilling off freed hydrocyanic acid, the decomposition of insoluble compound
cyanides with an alkaline hydrate or with milk of lime and their conversion thereby

page_text: into soluble compounds, and the obtainment of concentrated solutions by precipitating,
separating, and reconverting into soluble compounds, all substantially as and for the
purposes hereinbefore described.
Dated this 13th day of November 1880
ALLISON BROS,
Agents for the Applicant.