Improvements in the Manufacture of Cyanides and Ferro-cyanides from Sulpho-cyanides, and the Recovery of Bye-products.
Year: 1895

page_text: Date of Application, 1st June, 1895
Complete Specification Left, 25th Mar., 1896-Accepted, 16th May, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Cyanides and Ferro-cyanides
from Sulpho-cyanides, and the Recovery of Bye-products.
We, JULIUS RASCHEN, Ph.D. Analytical Chemist and JOHN BROCK, Director
of The United Alkali Company Limited both of G Exchange Buildings
Liverpool in the County of Lancaster, do hereby declare the nature of this
invention to be as follows:-
The manufacture of cyanides and ferro-cyanides from sulpho cyanides has hitherto
been attended with great difficulties. The separation of the sulphur contained in
the sulpho-cyanides has generally been attempted by treating the fused sulpho-
cyanide with a metal such as iron, zinc or lead. All these processes demand a high
temperature at which a considerable loss of cyanide is incurred owing to various
well known causes.
By our present invention we treat a sulphocyanide such a calcium sulpho-
cyanide with a mixture of an oxidising agent such as a nitrate, chromate, lead
peroxide, manganese peroxide or the like with water and an acid such as sulphuric
acid. We thus oxidise the sulphur contained in the sulphocyanide into sulphuric
acid and at the same time liberate the cyanogen in the form of hydrocyanic acid.
It is advisable that all the raw materials should be as free from chlorides as
possible.
We may proceed according to this invention as follows:
We mix the oxidising agent (such as sodium nitrate) with water and sulphuric
acid and add thereto a sulphocyanide such as calcium sulphocyanide the mixture
being contained in a vessel capable of being closed airtightly, and provided with an
agitator and an exit pipe or passage conducting the gases evolved during the
reaction to a suitable absorbing apparatus.
We gradually beat the mixture nearly to the boiling point of water when
decomposition takes place, the sulphur of the sulphocyanide being converted into
sulphuric acid which remains in the vessel together with the sulphates of the base of
the sulpho-cyanide and that of the oxidising agent, whilst hydrocyanic acid is liberated
and passes through the exit pipe or passage together with any other gases that may
be liberated.
As the reaction is rather violent we prefer to heat by itself the mixture of
the oxidising agent, water and sulphuric acid and then to add gradually to this
heated mixture the sulphocyanide either in solution or in suspension in water.
Towards the end of either operation the mixture is heated to boiling, in order
to expel the bydrocyanic acid. The residual liquor is then withdrawn and may be
treated in a suitable manner for the recovery of any base or acid or both which it
may contain.
The gaseous mixture of hydrocyanic acid, steam, and other gas is passed through,
or over, a solution of a caustic alkali or alkaline earth contained in a suitable
vessel or series of vessels which may be provided with agitators. The hydro-
cyanic acid combines with the caustic alkali or alkaline earth forms the
corresponding cyanide whereas the other gases, if any be present, pass through.
the vessel unabsorbed.
The solution of cyanide so obtained may be evaporated to dryness, which may
best be done in a vacuum pan whereby the cyanide is obtained in the solid state
or the solution of the cyanide may be treated with a salt or an oxide of iron and

page_text: converted into the corresponding ferrocyanide, which may be dealt with in the usual
way, so as to obtain the ferrocyanide in the crystalline form.
If a nitrate be the oxidising agent employed in the above process the hydro-
cyanic acid will be mixed with nitric oxide gas, which will pass unabsorbed through
the caustic alkali or alkaline earth, if care have been taken to. exclude air from
the apparatus. This nitric oxide can be recovered in the form of nitric acid, by
passing the gas issuing from the vessels in which the absorption of the hydrocyanic
acid has been completed, into another apparatus, where it is mixed with air and
steam as is well understood.
A tower containing coke, plates, or the like is
suitable for this purpose.
In carrying out this invention great care must be taken not to allow any of the
gases to escape into the air before they have been freed from the hydrocyanic acid
they contain. Owing to the poisonous properties of this substance it is necessary
to have all the vessels perfectly tight and it is advisable to maintain a slight
vacuum in all the vessels so as to prevent the possibility of any escape of
hydrocyanic acid.
Dated this 1st day of June 1895
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture of Cyanides and Ferro-cyanides
from Sulpho-cyanides, and the Recovery of Bye-products.
We, JULIUS RASCHEN Ph.D. Analytical Chemist and JOHN BROCK Director
of The United Alkali Company Limited both of G₁ Exchange Buildings,
Liverpool in the County of Lancaster 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:-
The manufacture of cyanides and ferrocyanides from sulphocyanides has hitherto
been attended with great difficulties. The separation of the sulphur contained in
the sulpho cyanides has generally been attempted by treating the fused sulpho-
cyanide with a metal such as iron, zinc, or lead. All these processes demand a high
temperature, at which a considerable loss of cyanide is incurred, owing to various
well known causes.
According to the present invention a sulpho-cyanide, such as calcium sulpho-
cyanide is treated with a mixture of an oxidizing agent, such as a nitrate,
chromate, lead peroxide, inanganese peroxide, or the like, with water, and an acid,
such as sulphuric acid. We thus oxidize the sulphur contained in the sulpho
cyanide into sulphuric acid and, at the same time, liberate the cyanogen in the form
of hydrocyanic acid. It is advisable that all the raw materials used should be as
free from chlorides as possible.
We may proceed according to this invention as follows:-
We mix the oxidizing agent (such as manganese peroxide for example) with
water and sulphuric acid and add thereto a sulpho cyanide, such as calcium sulpho
cyanide, the mixture being contained in a vessel capable of being closed air-
tightly, and provided with an agitator and an exit pipe, or passage, conducting
the gases, evolved during the reaction, to a suitable absorbing apparatus.
We gradually heat the mixture nearly to the boiling point of water, when
decomposition takes place, the sulphur of the sulpho cyanide being converted into
sulphuric acid, which remains in the vessel together with the sulphates of the base
of the sulpho cyanide and that of the oxidising agent whilst hydrocyanic acid is
liberated and passes through the exit pipe, or passage, together with any other gases
that may be liberated.

page_text: As the reaction is rather violent we prefer to heat by itself the mixture of the
oxidizing agent, water and sulphuric acid, and then to add gradually to this beated
mixture the sulpho cyanide either in solution or in suspension in water, taking care-
to have more of the oxidizing agent and acid present than is indicated by the
following equation
:-
mixture the sulpho cyanide either in solution or in suspension in water, taking care
to have more of the oxidizing agent and acid present than is indicated by the
following equation
NaCNS + 3 H₂SO, + 3 MnO2 = HCN + NaHSO, + 3 MnSO, + 2 H₂O
(choosing sodium sulpho-cyanide and manganese peroxide as examples).
Towards the end of this operation the mixture is heated to boiling in order to
expel the hydrocyanic acid. The residual liquor is then withdrawn, and may be
treated in a suitable manner for the recovery of any base, or acid, or both, which it
may contain.
The gaseous mixture of hydrocyanic acid steam and other gas is passed through,
or over, a solution of a caustic alkali, or alkaline earth, contained in a suitable
vessel, or series of vessels, which may be provided with agitators. The hydro-
cyanic acid combines with the caustic alkali, or alkaline earth, and forms the
corresponding cyanide.
-
The solution of cyanide so obtained may be evaporated to dryness, which may
best be done in a vacuum pan, whereby the cyanide is obtained in the solid state,
or the solution of the cyanide may be treated with a salt of iron, or an oxide of
iron, and converted into the corresponding ferrocyanide, which may be dealt with
in the usual way, so as to obtain the ferrocyanide in the crystalline form.
If a nitrate be the oxidizing agent employed in the above process the hydro-
cyanic acid will be mixed with nitric oxide gas, which will pass unabsorbed through
the caustic alkali, or alkaline earth, if care have been taken to exclude air from the
apparatus. This nitric oxide can be recovered in the form of nitric acid by passing
the gas, issuing from the vessels in which the absorption of the hydro cyanic acid
has been completed, into another apparatus where it is mixed with air and steam as
is well understood.
In carrying out this invention great care must be taken not to allow any of the
gases to escape into the air before they have been freed from the hydrocyanic
acid they contain. Owing to the poisonous properties of this substance it is
necessary to have all the vessels perfectly tight and it is advisable to maintain a
slight vacuum in all the vessels so as to prevent the possibility of any escape of
hydrocyanic acid.
We have found that when a nitrate is used as the oxidizing agent small amounts
of the higher oxides of nitrogen are present in the gases which pass into the
absorber and these higher oxides of nitrogen are absorbed together with the hydro-
cyanic acid, by the caustic alkali, or alkaline earth. In this case the solution of
the cyanide may, if desired, be evaporated to dryness, but should not be fused,
since on fusion, a mixture of nitrates, nitrites, and cyanides reacts violently. IE
fusion is to be resorted to removal of the higher oxides of nitrogen should be
effected by passing the gases into contact with hot water, by which the nitrous fumes
are retained. This treatment of the gases however we do not claim under the
present application as it is the subject of our application for Letters Patent
No. 21678 of the 14th November 1895.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is.
1. In the manufacture of cyanides, or ferrocyauides, from sulphocyanides; the
treatment of sulphocyanides with a mixture of an oxidizing agent, such as a
nitrate, a chromate, lead-peroxide, manganese-peroxide, or the like, and water, and
an acid, such as sulphuric acid; substantially as herein before described.
2. In the manufacture of cyanides, or ferrocyanides from sulphocyanides; the
treatment of sulphocyanides with a mixture of an oxidizing agent, such as a

page_text: nitrate, a chromate lead-peroxide, manganese-peroxide, or the like, and water, and
an acid, such as sulphuric acid, the mixture of the oxidising agent, water, and
acid, being first heated and then the sulphocyanide in solution or suspension, in
water, being gradually added; substantially as herein before described.
3. In the manufacture of cyanides or ferrocyanides, from sulphocyanides ;
treating sulpho cyanide with a mixture of an oxidizing agent, such as a nitrate,
a chromate, lead-peroxide, manganese-peroxide, or the like, and water, and an acid,
such as sulphuric acid, and passing the evolved gaseous mixture in contact with a
solution of a caustic alkali, or alkaline earth, so as to absorb the hydrocyanic acid;
substantially as herein before described.
4. In the manufacture of cyanides or ferrocyanides, from sulphocyanides;
treating sulphocyanides with a mixture of a nitrate, and water, and an acid, such as
sulphuric acid, and passing the evolved gaseous mixture in contact with a solution
of caustic alkali, or alkaline earth, so that the hydrocyanic acid is absorbed thereby,
and treating the nitric oxide, evolved with air, and steam, for converting it into
nitric acid; all substantially as herein before described.
Dated this 25th day of March 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.