Improvements in the Manufacture of Hydrogen Cyanide.
Year: 1899

page_text: Date of Application, 14th Sept., 1899
Complate Sonorification loft 14th June 1900-Accepted, 21st July, 1900
Date of Application, 14th Sept., 1899
Complate Specification Loft 11th June 1900-Accepted. 21st July, 1900
Improvements in the Manufacture of Hydrogen Cyanide.
I, EMIL BERINGER, Commerzienrath, of Sophienstrasse 1A, Charlottenburg,
Berlin, in the Empire of Germany, do hereby declare the nature of this invention
to be as follows:-
The known oxidising action of nitric acid on sulphocyanide, producing
hydrogen cyanide, may be expressed by the equation:-
Ba(CNS) + HNO₁ = BaSO4 + H₂SO, + HCN + 4NO
Various attempts have been made to render this reaction practically useful,
but all the processes devised suffer from the objection that in the course of the
reaction much of the hydrogen cyanide is oxidised to carbon dioxide, so that
the yield of hydrogen cyanide is too small, for profitable application of the
process.
I have found that the production of carbon dioxide in the process is due to the
action of free mineral acid, which in the case of the reaction expressed by the
above equation is sulphuric acid formed by the chemical change.
the re-
If, therefore, this production of carbon dioxide is to be suppressed
action must be carried out in such manner that no free acid is formed or can
become active, and it is to such manner of carrying out the process that my
invention relates.
For the purpose of avoiding the formation of free sulphuric acid I substitute
for the nitric acid requisite for the oxidation, an equivalent quantity of a nitrate
such as barium nitrate, calcium nitrate, or the like. If now an acid capable of
liberating nitric acid be allowed to act upon this nitrate, the nitric acid thus set
free will oxidise some of the sulphocyanide producing free sulphuric acid; the
latter, however, will react with the nitrate present to form a sulphate and to
In this
liberate more nitric acid which in its turn oxidises sulphocyanide.
manner the sulphocyanide may be oxidised without formation of free acid, as is
expressed by the following equation, in which the barium salts are used as
The production of carbon dioxide is reduced to a minimum when the oxidation
of a sulphocyanide is effected in this manner, and as a consequence the yield of
hydrogen cyanide is nearly that indicated by theory.
The following example serves to illustrate the process.
82 kilos. of barium nitrate are dissolved in 700 litres of water contained in a
retort provided with a stirrer. Into the boiling hot solution are poured either
separately, in small portions, or mixed together and gradually a solution of

page_text: 37.2 kilos. of barium sulphocyanide in 100 litres of water and a solution of
31.6 kilos of sulphuric acid, of specific gravity 1.84, in 100 litres of water. If
barium sulphocyanide or calcium sulphocyanide is used it is advantageous to
mix the solution of this salt with that of the sulphuric acid and to allow the
barium sulphate or calcium sulphate to settle before pouring the liquid into the
barium nitrate solution. The hydrogen cyanide liberated by the reaction distils
over with the steam and is worked up in the usual manner.
ABEL & IMRAY,
Agents for the Applicant.
hydrogen cyanide, may be expressed by the equation:
Ba (CNS), + HNO,
=
BaSO+H,CO, +. HCN + INO
Various attempts have been made to render this reaction practically useful,
but all the processes devised suffer from the objection that in the course of the
reaction much of the hydrogen cyanide is oxidised to carbon dioxide, so that
the yield of hydrogen evanide is too small for profitable application of the
process.
I have found that the production of carbon dioxide in the process is due to the
action of free mineral acid, which in the case of the reaction expressed by the
above equation is sulphuric acid formed by the chemical change.
If, therefore, this production of carbon dioxide is to be suppressed, the re-
action must be carried out in such manner that no free acid is formed or can
become active, and it is to such manner of carrying out the process that my
invention relates.
For the purpose of avoiding the formation of free sulphuric acid I substitute
for the nitric acid requisite for the oxidation of the sulphocyanide an equivalent
quantity of a nitrate such as barium nitrate, calcium nitrate or the like from
which free nitric acid is liberated by the addition of a mineral acid, sulphuric
acid for instance. It is however essential for the purpose of my invention to
use the mineral acid only in such quantities that the mixture shall retain a
neutral reaction, so that I use only half the amount of mineral acid which would
correspond with the entire amount of nitrate present. It is also essential for
the purpose of my invention to add the previously prepared mixture of this
mineral acid with the sulphocyanide to the nitrate. Or I may introduce the
mineral acid and the sulphocyanide separately into the nitrate. I am thus en-
abled to control the reaction and to avoid the formation of an excess of mineral
acid which would act injuriously upon the products of the reaction.
Using barium nitrate as an instance, the reaction may be expressed by the
following equation :.

page_text: is reduced to a minimum and the yield of hydrogen cyanide approaches that
indicated by the theory.
The following example serves to illustrate the process.
82 kilos. of barium nitrate are dissolved in 700 litres of water contained in a
retort provided with an agitator. Into the boiling hot solution are poured either
separately, in small portions, or mixed together and gradually a solution of
37.2 kilos. of barium sulphocyanide in 100 litres of water and a solution of
If
15.8 kilos. of sulphuric acid, of specific gravity 1.84, in 100 litres of water.
barium sulphocyanide or calcium sulphocyanide is used it is advantageous to allow
the barium sulphate or calcium sulphate to settle and only to use the clear super-
natant solution. The hydrogen cyanide liberated by the reaction distils over
with the steam and is worked up in the usual manner.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I wish it to be under-
stood that I am aware that in the manufacture of cyanides or ferrocyanides
from sulphocyanides, the sulpho-cyanides have been treated 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 I make
no general claim to such treatment but I declare that what I claim is:-
The herein described manufacture of hydrogen cyanide from sulphocyanides
by treating a nitrate with a solution of a sulphocyanide and a mineral acid, the
said solution and acid being added to the nitrate either mixed together or sepa-
rately, and the quantity of acid being half that which is equivalent to the
quantity of nitrate.
Th: 11th low of Tune 1000