Improvements in and Apparatus for the Manufacture of Cyanides and Ferrocyanides from Sulphocyanides, and the Recovery of Bye- Products.
Year: 1898

page_text: Date of Application,
L
Sept.,
4000
Complete Specification Left, 5th June, 1899-Accepted, 15th July, 1899
Date of Applicatio
Complete Specification Lelt, 5th June, 1899-Accepted, 15th July, 1899
PROVISIONAL SPECIFICATION.
Improvements in and Apparatus for the Manufacture of Cyanides and
Ferrocyanides from Sulphocyanides, and the Recovery of Bye-
Products.
We, JULIUS RASCHEN, Ph.D., Analytical Chemist, and THE UNITED ALKALI
COMPANY LIMITED, both of G 11, Exchange Buildings, Liverpool, in the County
of Lancaster, do hereby declare the nature of this invention to be as follows:-
Letters Patent Nos. 10476, 10956 and 21678 all of 1895 relate to the manu-
facture of cyanides and ferrocyanides from sulpho cyanides by treating a sulpho-
cyanide (dissolved or suspended in water) by means of an oxidising agent, such
as nitric acid, or a mixture of sulphuric acid with a nitrate, chromate, lead
peroxide, manganese peroxide or the like. The decomposition in all cases is a
similar one, the sulphur in the sulphocyanide being converted into sulphuric
As the economical manufacture
acid and hydrocyanic acid being liberated.
depends on the easy recovery of the oxidising agent we prefer to employ nitric
acid, which by its action on sulphocyanides is reduced to nitric oxide which latter
is readily recovered as nitric acid.
The object of the present invention is to provide means by which this process
can be carried out in a better manner than heretofore.
A series of jars, or vessels, is used (hereinafter termed decomposers) made of
stoneware, cast iron lined with ebonite, or other suitable material. Into the first
of these decomposers which contains either water or mother liquor from a pre-
vious operation the sulphocyanide (in solution or in suspension in water) is
gradually introduced the whole being maintained at, or near the boiling point by
the introduction of steam. Simultaneously nitric acid or a mixture of sulphuric
acid and nitrate of soda, is admitted at such a rate that there shall always be an
When the reaction has commenced and the nitric acid is
excess of nitric acid.
being recovered, as hereinafter described the amount of nitric acid, or sulphuric
acid and nitrate of soda, to be added is reduced to an amount necessary to make
The decomposers
up for an unavoidable loss in the process of manufacture.
should be in such number that the liquor flowing off from the last of them (con-
sisting mainly of acid sulphate of soda, in case sodium sulphocyanide be the
sulphocyanide employed) is practically free from hydrocyanic acid. The liberated
gases consisting of hydrocyanic acid nitric oxide, a small quantity of the higher
oxides of nitrogen, and a little carbonic acid are next passed through a suitable
wash tower, or scrubber, constructed of stoneware, cast iron lined with ebonite,
or other suitable material, and containing broken bricks or equivalent material
down which water is caused to flow. The heat conveyed by the gases from the
decomposers is sufficient to maintain the wash tower or scrubber at such a tem-
perature that although complete removal of higher oxides of nitrogen is ensured
very little absorption of hydrocyanie acid takes place. The liquor from this wash
tower or scrubber, containing nitric acid and a little hydrocyanic acid, is con-
veyed through suitable pipes, into the first decomposer, to be used over again.

page_text: The gases issuing from the wash tower or scrubber, are next passed into a con-
denser (preferably made of cast iron) in which they are cooled. The condensed
water being saturated with hydrocyanic acid is conducted through pipes into the
second decomposer in order that the hydrocyanic acid may be recovered.
The cooled gases are passed into a cast iron absorbing vessel, or cast iron
absorbing vessels, containing a solution of caustic alkali or alkaline earth corre-
sponing to the cyanide required, which absorbs the hydrocyanic acid to form
the cyanide and allows the nitric oxide to pass on. The said absorber or
absorbers is or are preferably water jacketted to counteract the heat which is
given off by the absorption of hydrocyanic acid in caustic alkali and to thus
avoid any decomposition in the early part of the absorption process.
The nitric oxide which passes unabsorbed through the caustic alkali, or alka-
line earth, is next conducted through cast iron pipes into stoneware towers
packed with bricks or the like, down which water is caused to flow, sufficient air
being admitted to convert the nitric oxide into nitric acid. The recovered nitric
ac. is conducted through suitable pipes back to the leading decomposer to be
re-used or a further conversion of sulphocyanide into cyanide.
The solution of cyanide obtained by the absorption of hydrocyanic acid in
caustic athati is advantageously boiled down to dryness in a vacuum, to avoid the
decomposition of cyanide into ammonia.
The solution of alkaline cyanide may, if desired, be converted into the corre-
sponding 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 necessary 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.
Dated this 17th day of September 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
İmprovements in and Apparatus for the Manufacture of Cyanides and
Ferrocyanides from Sulphocyanides. and the Recovery of Bye-
products.
We, JULIUS RASCHEN, Ph.D., Analytical Chemist, and THE UNITED ALKALI
COMPANY LIMITED, both late of G. 11, Exchange Buildings, now of 30, James
Street, Liverpool, in the County of Lancaster, England, 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; -
Letters Patent Nos. 10476, 10956 and 21678 all of 1895 relate to the manu-
facture of cyanides and ferrocyanides from sulphocyanides, by treating a sulpho-
cyanide (dissolved or suspended in water) by means of an oxidising agent, such
as nitric acid, or a mixture of sulphuric acid with a nitrate, chromate, lead
peroxide, manganese peroxide, or the like. The decomposition in all cases is a
similar one; the sulphur in the sulphocyanide being converted into sulphuric
acid and hydrocyanic acid being liberated. As the economical manufacture
depends on the easy recovery of the oxidising agent, we prefer to employ nitric
acid, which by its action on sulphocyanides is reduced to nitric oxide which latter
is readily recovered as nitric acid.

page_text: The object of the present invention is to provide means by which this process
can be carried out in a better manner than heretofore.
We will explain this invention with reference to the accompanying diagram-
matic elevation (Figure 1) and plan (Figure 2) of a plant arranged in accordance
therewith.
A series of jars, or vessels A to A is used (hereinafter termed decomposers)
made of stoneware, cast iron lined with ebonite, or other suitable material and
in communication with each other by the overflow pipes a. In starting the
process the decomposers contain water to the level of the overflow pipes and into
the first of these the sulphocyanide (in solution, or in suspension, in water)
together with nitrate of soda is gradually introduced by the syphon the whole
being maintained at, or near, the boiling point (say about 96 to 97 degrees Centi-
grade) by the introduction of steam by the pipes c. Simultaneously sulphuric
acid is admitted by the syphon d. Care must be taken that there shall always
be an excess of nitric acid. When the reaction has commenced and the nitric
acid is being recovered, as hereinafter described, the amount of sulphuric acid
and nitrate of soda (or nitric acid) to be added is reduced to an amount necessary
to make up for an unavoidable loss in the process of manufacture. The decom-
posers should be in such number that the liquor flowing off from the last of
them (A) (consisting mainly of acid sulphate of soda, in case sodium sulpho-
cyanide be the sulphocyanide employed) is practically free from hydrocyanie
acid. We have shown nine decomposers as being a suitable number for example.
The liberated gases consisting of hydrocyanic acid, nitric oxide, a small quantity
of the higher oxides of nitrogen, and a little carbonic acid, are next passed with
the steam which is also given off through a wash tower, or scrubber, E con-
structed of stoneware, cast iron lined with ebonite, or other suitable material,
and containing broken bricks, or equivalent material, down which water is caused
to flow. The heat conveyed by the gases from the decomposers is sufficient to
maintain the said wash tower, or scrubber, at such a temperature that although
complete removal of higher oxides of nitrogen is ensured, very little absorption
of hydrocyanic acid takes place. The liquor from this wash tower, or scrubber,
containing nitric acid, and a little hydrocyanic acid, is conveyed, through the
pipe f into the first decomposer, to be used over again.
The gases issuing from the wash tower, or scrubber, are next passed by the
pipe g through the coil of a condenser H (preferably made of cast iron) in which
the said gases are cooled. The liquid which condenses from the vapours, and
which is saturated with hydrocyanic acid, is conducted through the trap or box i
and pipe into the second decomposer A2 in order that the hydrocyanic acid
may be recovered. The cooled gases pass from the box i and by the pipes j into
an absorbing vessel or absorbing vessels, (we have shewn two at K) (preferably
of cast iron) containing caustic alkali, or alkaline earth, in solution or suspension
(admitted at ) corresponding to the cyanide required, which absorbs the hydro-
evanic acid to form the cyanide and allows the nitric oxide to pass on. The said
absorber, or absorbers, is, or are, preferably water jacketted to counteract the
heat which is given off by the absorption of hydrocyanic acid in caustic alkali,
and to thus avoid any decomposition in the early part of the absorption process.
The nitric oxide not being absorbed by the caustic alkali, or alkaline earth, is
conducted by the pipes 7 into a stoneware tower or stoneware towers (we have
shewn three at M) packed with bricks, or the like, down which cold water is
caused to flow, sufficient air being admitted to convert the nitric oxide into nitric
acid. The recovered nitric acid is conducted through the pipe back to the lead-
ing decomposer A¹ to be reused for a further conversion of sulpho cyanide into
cyanide.
The solution of cyanide obtained by the absorption of hydrocyanic acid in
caustic alkali is advantageously boiled down to dryness in a vacuum, to avoid the
decomposition of cyanide into ammonia.
The solution of alkaline cyanide may, if desired, be converted into the corre-

page_text: sponding 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 necessary 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 the said
invention and in what manner the same is to be performed, we declare that what
we claim is:
_
1. The manufacture of cyanides and ferrocyanides from sulphocyanides by
causing the sulphocyanide together with nitric acid, to pass through a series of
decomposers to which steam is admitted from which the gases and vapours
evolved are passed through a water wash-tower and thence to a condenser and
thence to absorbers containing caustic alkali, or alkaline earth, by which the
hydrocyanic acid is absorbed the nitric oxide passing through a tower, or towers,
in which it becomes converted to nitric acid, and is returned to the decomposers
for re-use in the process, the liquor from both the aforesaid water wash-tower and
condenser being conducted back to the decomposers; all substantially as here-
inbefore described.
2. Apparatus for the manufacture of cyanides and ferrocyanides from sulpho-
cyanides, the said apparatus consisting of the combination of decomposers, with
inlets for the sulpho cyanide and the nitric acid, or nitric acid-forming materials,
and for steam, and communications for the gases and vapours evolved to a water
wash tower, provided with communications for the gases to a condenser and for
liquid back to the decomposers, and the said condenser provided with communi-
cations for liquid back to the decomposers, and for gases to an absorber, or
absorbers, which absorbers are provided with a communication with a tower, or
towers, in which nitric acid is re-formed and which have communication with the
decomposers for the return of the nitric acid thereto; all substantially as herein-
before described and illustrated in the accompanying drawings.
Hated this 5th Jo of Luna 1800
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.