Improvements in the Manufacture of Cyanides and Ferrocyanides from Sulphocyanides, and the Recovery of Bye-products.
Year: 1895

page_text: Date of Application, 27th May, 1895
Complete Specification Left, 25th Mar., 1896-Accepted, 16th May, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Cyanides and Ferrocyanides
from Sulphocyanides, 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 ferrocyanides from sulphocyanides has
hitherto been attended with great difficulties. The separation of the sulphur
contained in the sulphocyanides has generally been attempted by treating the
All these processes
fused sulphocyanide with a metal such as iron or ziuc or lead.
however demand a high temperature at which a considerable loss of cyanide is
incurred owing to various well known causes.
According to the present invention the separation of the sulphur contained in
the sulphocyanide is effected by treating such sulphocyanide, mixed or dissolved
in water, with an oxidising agent (nitric acid for example) which converts the
sulphur into sulphuric acid and liberates the cyanogen in the form of hydro-cyanic
acid. We may proceed according to this invention as follows.
We mix a sulphocyanide (say for example calcium sulphocyanide) with water
and nitric acid in a closed vessel provided with an exit pipe or passage for the
escape of the gases liberated during the reaction, which pipe or passage conveys
these gases to a suitable absorbing apparatus.
Atmospheric air must be excluded from the vessel. We gradually heat the
mixture to boiling. By this operation the sulphur of the sulphocyanide is
converted into sulphuric acid which remains together with the base of the sulpho-
cyanide in the solution, whilst the hydrocyanic acid formed passes away through
the exit pipe or passage with the nitric oxide gas and with some steam.
prefer to add the sulpbocyanide (dissolved or suspended in water) gradually to
the boiling mixture of nitric acid and water. The vessel may be provided with
an agitator.
We
When the whole of the hydrocyanic acid has been driven off, which may be
ascertained by testing a sample from time to time, the solution may be run off and
the contained base or acid or both be recovered.
The gaseous mixture of hydrocyanic acid, nitric oxide and steam is passed
according to this invention through, or over, a solution of a caustic alkali or
alkaline earth, contained in a vessel or series of vessels, which may be provided
with agitators and be so arranged with inlet and outlet pipes that the gases pass
from vessel to vessel. The hydrocyanic acid is absorbed and combines with the
alkali, or alkaline earth to form a cyanide.
The nitric oxide, which if air has been excluded does not combine with the
alkali or alkaline earth, passes onto a suitable apparatus wherein it is mixed with
air and steam for the purpose of reconverting it into nitric acid which condenses
and may be used again for treating a further quantity of sulphocyanide.
The solution of cyanide formed by the absorption of the hydrocyanic acid in
the caustic alkali or alkaline earth may be evaporated to dryness if a cyanide be
If a
required the evaporation being advantageously performed in a vacuum pan.
ferrocyanide be required the solution of the cyanide may be treated with a salt, or

page_text: an oxide of iron or a salt, or oxide of iron may be added to the caustic alkali in
the absorbing vessel before, or during, the operation of absorption.
Owing to the poisonous properties of hydrocyanic acid and of the cyanides it is
necessary to operate with great care, and it is advisable to maintain a slight vacuum in
the apparatus so that no gases may leak out into the atmosphere, should the
apparatus become leaky. But no air should enter the apparatus as then the nitric
oxide would be oxidised to nitric peroxide and absorbed by the caustic alkali, and
the resulting cyanide would be contaminated with nitrites and nitrates, and
necessitate the conversion of the cyanide into the less valuable ferrocyanide for the
purpose of separation of the several salts by crystallisation.
Dated this 27th day of Now 1905
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture of Cyanides and Ferrocyanides
from Sulphocyanides, 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 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 ferro-cyanides from sulpho-cyanides has
hitherto been attended with great difficulties.
The separation of the sulphur contained in the sulpbo-cyanides has generally
been attempted by treating the fused sulpho-cyanide with a metal such as
iron, or zinc, or lead. All such processes however demand a high temperature
at which a considerable loss of cyanide is incurred owing to various well known
causes.
According to the present invention the separation of the sulphur contained in
the sulphocyanide is effected by treating such sulphocyanide (mixed or dissolved in
water) with nitric acid which converts the sulphur into sulphuric acid and liberates
the cyanogen in the form of hydrocyanic acid. It is advisable that all raw materials
used should be as free from chlorides as possible.
The main reaction which takes place when a sulphocyanide is thus treated with
nitric acid may be represented by the following equation in which sodium sulpho-
cyanide is taken as an example.
NaCNS +2 HN.O₁ = HCN + 2 NO + NaHSO
We may practically carry out this invention as follows:-
We mix a sulpho cyanide, such as sodium or calcium sulpho-cyanide, with about,
four to five times its weight of water and we allow this mixture to flow gradually
into a closed vessel containing some water (or mother liquor from a previous
operation) which we maintain at, or near, its boiling point say about 96° Centigrade.
Simultaneously we admit nitric acid into the vessel through a separate pipe at such
a rate that there shall always be fiee nitric acid in the vessel. Excess of sulpho-
cyanide should be avoided. The closed vessel is provided with an exit pipe, or
passage, for the escape of the gases liberated during the reaction which pipe
or passage conveys these gases to a suitable absorbing apparatus. A stirrer or
agitator should also be provided in the said vessel in order to stir up the contents
especially when the sulphocyanide is not a soluble one. Atmospheric air must be
excluded from the vessel so as to avoid oxidation of the nitric oxide. By this

page_text: operation the sulphur of the sulphocyanide is converted into sulphuric acid which
remains in the vessel together with the base of the sulphocyanide whilst the hydro-
cyanic acid formed passes away through the exit pipe, or passage, with the nitric
oxide gas, and with some steam.
When the whole of the hydrocyanic acid has been driven off (which may be
ascertained by testing a sample from time to time) the solution may be run off and
the base, or acid, or both, be recovered.
The gaseous mixture of hydrocyanic acid, nitric oxide and steam, is passed,
according to this invention, through or over, a solution of a caustic alkali, or
alkaline earth, contained in an absorbing vessel, or series of absorbing vessels, which
may be provided with agitators and be so arranged with inlet and outlet pipes, that
the gases pass from vessel to vessel.
The hydrocyanic acid is absorbed and combines with the alkali, or alkaline
earth, to form a cyanide. The nitric-oxide does not combine with the alkali or
alkaline earth, but passes on to a suitable apparatus wherein it is mixed with air
and steam, for the purpose of reconverting it into nitric acid, which condenses, and
may be used again for treating a further quantity of sulphocyanide.
The solution of cyanide formed by the absorption of the hydrocyanic acid in the
caustic alkali, or alkaline earth, may be evaporated to dryness if a cyanide be
required, the evaporation being advantageously performed in a vacuum pan as we
have found that small amounts of the higher oxides of nitrogen are present in the
gases which pass into the absorber and these are absorbed with the hydrocyanic
acid by the solution of caustic alkali, or alkaline earth, it will not be safe to heat
the solution to the fusion point of cyanide, and therefore, if the cyanide is to be
obtained in the dry, or anhydrous, state, the gases before passing into the absorber
should have such higher oxides of nitrogen removed therefrom 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 14th November 1895.
If a ferrocyanide be required the solution of the cyanide may be treated with a
salt of iron, or an oxide of iron, or a salt of iron, or an oxide of iron may be
added to the solution of caustic alkali, or alkaline earth, in the absorbing vessel or
vessels, before or during the operation of absorption.
Owing to the poisonous and dangerous properties of hydrocyanic acid, and of the
cyanides, it is necessary to operate with great care and it is advisable to maintain.
a slight vacuum in the apparatus, so that no gases may leak out into the atmosphere
should the apparatus become leaky. But no air should enter the apparatus as then
the nitric oxide would be oxidised to nitric peroxide and be absorbed by the
solution of caustic alkali or alkaline earth, and the resulting cyanide would
be contaminated with nitrites and nitrates and necessitate the conversion of the
cyanide into the less valuable ferrocyanide for the purpose of separation of the
several salts by crystallisation.
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 ferro-cyanides from sulpho-cyanides, the
treatment of sulphocyanide (dissolved or suspended in water) with nitric acid;
substantially as herein before described.
2. In the manufacture of cyanides, or ferro-cyanides from sulpho-cyanides, the
treatment of sulpho-cyanide, dissolved, or suspended, in water, with nitric 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 ;
substantially as herein before described.
3. In the manufacture of cyanides, or ferro-cyanides, from sulpho cyanides, the
treatment of sulpho-cyanide, dissolved or suspended, in water, with nitric acid and
passing the evolved gaseous mixture in contact with a solution of caustic alkali, or

page_text: alkaline earth so that the hydrocyanic acid is absorbed thereby, and treating the
nitric-oxide with air and steam for reconverting it into nitric acid substantially as
herein before described.
Dated the 25th day of March 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.