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

page_text: 'Date of Application, 14th Nov., 1895
Complete Specification Left, 12th Aug., 1896-Accepted, 19th Sept., 1836
Improvements in the Manufacture of Cyanides and Ferrocyanides
from Sulphooyanides, and in the Recovery of Bye-products.
We JULIUS RASCHEN Ph.D. Analytical Chemist and JOHN BROCK a 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 has hitherto always been attended
with great difficulties and has involved losses of cyanide from various well known
Causes.
The removal of the sulphur from the sulphocyanide has usually been attempted
by heating the sulphocyauide either with a metal such as iron, zinc, or lear, or
with a mixture of an alkaline earth and carbon.
These processes demand a high temperature, are costly, and give unsatisfactory
results.
By the present invention we effect the separation of the sulphur contained in the
sulphocyanide by treating such sulphocyanide dissolved in water (or in case the
sulphocyanide should be an insoluble oue then suspended in water) by means of an
oxidising agent, which converts the sulphur in the sulphocyanide into sulphuric
acid and at the same time liberates the cyanogeu in the form of hydrocyanic acid.
We may use for example as oxidising agents eithor nitric acid, or a mixture of
sulphuric acid with a nitrate, chromate, lead peroxide, manganese peroxide, or the
like, but as the economical manufacture depends on the recovery of the oxidising
agent and this is most readily accomplished when nitric acid is used as the
oxidising agent we prefer to employ nitric acid.
This invention may be carried out as follows:-We mix nitric acid with water
or we employ a mixture of sodium nitrate, sulphuric acid, and water, in a suitable
vessel capable of withstanding the action of the oxidising agent, and we heat this
to a suitable temperature, preferably a little bolow the boiling point of water in
order to have as little steam as possible in the gas. To this we slowly add the
sulphocyanide, dissolved or suspended in water (according to whether the sulpho-
cyanide is soluble or not) when the sulphur of the sulphocyanide is oxidised to
sulphuric acid and the cyanogen liberated in the form of hydrocyanic acid.
During the whole operation care must be taken to exclude all air, and the raw
materials should be as free from chlorides as possible.
The liberated gases, vapours, or fumes, consisting of hydrocyanic acid, nitric
oxide, water vapour, and a small quantity of nitrous fumes and carbonic acid gas,
are first passed through a scrubber containing water heated to about 80° Centigrade
which retains the nitrous fumes, allowing hydrocyanic acid, steam, nitric oxide, and
carbonic acid gas, to pass on into the absorbing tapparatus. This mixture of
hydrocyanic acid, steam, nitric oxide, and carbonic acid, after cooling if necessary,
is passed into a vessel, or series of vessels, containing cold water, or into a tower
containing any suitable material presenting a large extent of surface down which
cold water is allowed to run. The cold water absorbs the bydrocyanic acid but
allows the nitric oxide and carbonic acid to pass off and as these may contain traces
of hydrocyanic acid they are passed through lime water, when carbonate of lime
is precipitated and cyanide of calcium remains in solution. The cyanide may be
treated with an alkaline carbonate to obtain the alkaline cyanide. The gas escaping

page_text: from this lime scrubber now only consists of nitric oxide which we mix with steam
and air and treat in the usual way for the recovery of nitric acid.
The solution of hydrocyanio acid is neutralised with a solution of a caustic base,
such as caustic soda or potash, to obtain the required cyanide and is evaporated to
dryness in a suitable vessel. This is advantageously done in a vacuum. The
solution of alkaline cyanide may, if desired, be converted into the corresponding.
ferrocyanide by treatment with iron salts, as is well understood, when, by concen-
tration and crystallisation, the ferrocyanide can be obtained.
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 uo gases may escape into the atmosphere should
the apparatus become leaky but air must be prevented from entering the
apparatus.
Dated this 14th day of November 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields,, London, W.C., Agents.
Improvements in the Manufacture of Cyanides and Ferrocyanides
from Sulphocyanides, and in the Recovery of Bye-products.
We, JULIUS RASCHEN Ph.D. Analytical Chemist and JOHN BROCK a 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 perforined to be particularly described and ascer-
tained in and by the following statement :-
The manufacture of cyanides and ferrocyanides as hitherto practised has always
been attended with great difficulties, and has involved losses of cyanide from various
well known causes.
The removal of the sulphur from the sulphocyanide bas usually been attempted
by beating the sulphocyanide either with a metal, such as iron, zinc, or lead, or
with a mixture of an alkaline earth and carbon.
These processes demand a high temperature are costly and give unsatisfactory
results.
In the Specifications of Letters Patent Nos. 10476 and 10956 of 1895 we
describe the separation of the sulphur contained in the sulphocyanide by treating
such sulphocyanide, dissolved in water, (or in case the sulphocyanide should be an
insoluble one then suspended in water) by means of an oxidising agent such as
nitric acid, which converts the sulphur in the sulphocyanide into sulphuric acid,
and at the same time liberates the cyanogen in the form of hydrocyanic acid, or we
use as the oxidising agent, a mixture of sulphuric acid with a nitrate, chromate,
lead peroxide, manganese-peroxide, or the like, but as the economical manufacture
depends on the recovery of the oxidizing agent, and this is most readily accom-
plished when nitric acid is used as the oxidizing agent we prefer to employ nitric
acid as stated in the aforesaid Specification of Letters Patent No. 10476 of 1895.
The main reaction which takes place when a sulpho cyanide is thus treated with
nitric acid, may be represented by the following equation choosing sodium sulpho-
cyanide as an example.

page_text: four, to five, times its weight of water, and allow this mixture to flow gradually
into a closed vessel or "still" containing some water, or mother liquor, from a
previous operation, which we maintain at or near, its boiling point (say 96° Centi-
grade). Simultaneously we admit nitric acid, or a solution of nitrate of soda mixed
with sulphuric acid, into the vessel through a separate pipe at such a rate that
there shall always be free nitrio aoid in the vessel. The vessel should be provided
with a stirrer or agitator. Excess of sulpho-cyanide should be avoided. By this
operation the sulphur of the sulphocyanide is oxidised to sulphuric acid, and the
cyanogen is liberated in the form of hydrocyanic acid.
During the whole operation care must be taken to exclude all air so as to avoid
oxidation of the nitric oxide and the raw materials should be as free from chlorides
as possible.
The liberated gases, vapours, or fumes, consisting of hydrocyanic acid, nitric
oxide, water vapour, and a small quantity of higher oxides of nitrogen (technically
called nitrous fumes) and carbonic acid gas, are first passed into contact with hot
water which is most conveniently done by passing them through a scrubber
containing water heated to about 80° Centigrade which retains the nitrous fumes.
The dilute solution of nitric acid formed by the absorption of the nitrous fumes
in the scrubber may be passed through the still in order to utilize the nitric acid,
and to avoid the loss of any hydrocyauic acid it may contain.
The mixture of hydrocyanic acid, water vapour, nitric oxide, and carbonic acid
gas, after cooling if necessary, is passed into a vessel or into vessels containing a
solution of alkali or alkaline earth as in the process of our aforesaid former
specifications but in order to avoid as much as possible the contamination of the
cyanides with carbonates we prefer to absorb the hydrocyanic acid, (whether
prepared as directed in this specification, or as directed in our said former specifi-
cations,) in cold water. For this purpose we pass the gas (either from the still or
from the scrubber as the case may be) into a vessel, or series of vessels containing
cold water, or into a tower containing any suitable material presenting a large
extent of surface, down which cold water is allowed to run: The cold water
absorbs the hydrocyanic acid but allows the nitric oxide and carbonic acid to pass
on, and, as these may contain traces of hydrocyanic acid, they can be passed
through lime water when the hydrocyanic and the carbonic acid are absorbed,
carbonate of lime being precipitated, and cyanide of calcium remaining in solution.
The solution of calcium cyanide, thus obtained may be treated with an alkaline
carbonate to obtain the alkaline cyanide.
The gas escaping from this lime scrubber now consists of nitric oxide, which
we mix with steam and air and treat in the usual way for the recovery of nitric
acid.
The
The solution of hydrocyanic acid is neutralised with a solution of a caustic base,
such as caustic soda, or potash, to obtain the required cyanide and is evaporated to
dryness in a suitable vessel. This is advantageously done in a vacuum.
solution of alkaline cyanide may, if desired, be converted into the corresponding
ferrocyanide by treatment with iron salts, as is well understood, when, by
concentration and crystallization, the ferrocyanide can be obtained.
Owing to the poisonous properties of hydrocyanic acid and of the cyanides it is
pecessary to operate with great care, and it is advisable to maintain a slight vacuum
in the apparatus so that no gases may escape into the atmosphere should the
apparatus become leaky, but air must be prevented from entering the apparatus.
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 sulpho-cyanide, dissolved or suspended, in water, with an oxidising
agent, such as nitric acid, or a mixture of sulphuric acid with a nitrate, and passing
the evolved gaseous mixture into contact with heated water by which the nitrous

page_text: fumes are retained, the remaining gases and vapours being then passed into, or in
'contact with, cold water, or other medium, by which the 'hydrocyanic acid ia
'absorbed for obtainment, or for subsequent obtainment, of the cyanide ; 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 an oxidising
"agent, such as nitric acid, or a mixture of sulphuric acid with a nitrate, and passing
the evolved gaseous mixture into contact with heated water, whereby the nitrous
fumes are retained, the remaining gases and vapour 'being then passed into, or in
"contact with, cold water or other medium, by which the hydrocyanic acid is absorbed
for obtainment, or for subsequent obtainment, of the cyanido, 'the nitric oxide and
carbonic acid, with traces of hydrocyanic acid, being passed through or in contact
with lime-water to obtain cyanide, the escaping nitric oxide being then treated
'with steam and air for the obtainment of nitric acid; substantially as hereinbefore.
'described.
3. In the manufacture of cyanides, or 'ferro-cyanides from sulpho-cyanides, the
-treatment of sulpho-cyanide 'dissolved, or suspended in water, with an oxidising
'agent, such as nitric adid, or a mixture of sulphuric acid with a nitrate, and passing
the evolved gaseous mixture into contact with heated water whereby the nitrous
fumes are retained, the remaining gases and vapour being passed into, or in contact
with cold water, or other medium by which the hydrocyanic acid is absorbed for
obtainment, or 'for subsequent obtainment, of the cyanide; the escaping nitric
'oxide being then treated with steam and air for the obtainment of nitric acid
substantially as herein before described.
4. In the manufacture of cyanides or ferro-cyanides from sulpho-cyanides, treating
sulpho-cyanides with an 'oxidizing agent and passing the evolved gaseous mixture
in contact with 'or into cold water by which the hydrocyanic acid is absorbed for
subsequent obtainment of the cyanide; substantially as hereinbefore described.
Dated this 12th day of August 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.