Improved Process for Obtaining Cyanogen Combinations from Coal Gases.
Year: 1899

page_text: Date of Application, 15th June, 1899-Accepted, 25th Nov., 1899
COMPLETE SPECIFICATION.
Improved Process for Obtaining Cyanogen Combinations from Coal
Gases.
I, Dr. HERMANN TEICHMANN, Chemist, of Rheinau, Baden, in the Empire of
Germany, 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:-
Cyanogen is obtained from lighting gas almost exclusively by the so-called
dry purification process by means of oxide of iron, while no attempt has been
made to obtain the cyanogen contained in coke and foundry gases, owing to dry
purification not being practicable, in view of the enormous masses which would
have to be treated in this respect.
The present invention has for its object the obtaining from coal gases,-con-
taining cyanide of ammonium, or the components hydrocyanic acid and ammonia
as well as greater portions of sulphide of hydrogen-the valuable cyanogen,
separate from the processes for obtaining ammonia and sulphur. The process
is based on the observation that cyanide of ammonium, without the presence of
a fixed alkali, acts energetically on freshly formed or precipitated sulphide of
iron and sulphide of zinc, resulting in the production of cyanide of iron and
cyanide of zinc respectively, and cyanide of ammonium, easily soluble in water,
and sulphide of ammonium. If gases containing cyanide of ammonium are
introduced into water which contains precipitates of sulphide of iron in suspen-
sion, the sulphide of iron is dissolved in proportion as cyanide of ammonium is
absorbed. The chemical process which takes place may be expressed as follows:-
FeS + 6NH,CN= FeCN2 + 4NHCN + (NH4)2S
By far the greatest part of the cyanogen therefore is contained in the solution,
while a very small proportion of the cyanide of iron combination remains undis-
solved besides undecomposed sulphide of iron. Sulphide of hydrogen and car-
bonic acid have no effect on the thus produced ferro-cyanide of ammonium.
The process offers a very simple and convenient means of obtaining from coke
and foundry-coal-gases, from which the ammonia has been extracted, cyanogen
combinations, by interposing after the tar-separating and ammonia-absorption
apparatus, another suitable absorption apparatus.
Inasmuch as the alteration of the sulphide of iron takes place very rapidly,
and the latter having little disposition to settle down owing to which stopping
of the apparatus does not take place, the scrubbers used in the process for obtain-
ing ammonia can be employed. The standard washer employed in the lighting
gas manufacture can be used for this purpose with great advantage.
In operations on a large scale solutions of sulphate of iron are introduced into
the washings; these are immediately changed by the sulphide of hydrogen and
ammonium into sulphide of iron and ammonium sulphate. The cyanide of am-
monium contained in the gas reacts now on the sulphide of iron producing ferro-
cyanide of ammonium, which passes into solution. When the greater part of

page_text: the sulphide of iron has passed through the reaction a further quantity of sul-
phide of iron or of sulphate of iron is added, by which means the percentage of
ferro-cyanide of ammonium in the solution is increased. The further treatment
of the solution of ferro-cyanide of ammonium for obtaining cyanide is exceed-
igly simple, inasmuch as, for instance, chloride of calcium can be added to
the solution in order to precipitate insoluble ferro-cyano-calcium ammonium.
The precipitate consisting of sulphide of iron and cyanide of iron can be used
for further absorption.
While the cyanogen is obtained in the form of ferro-cyanogen combinations
when using iron salts, very valuable cyanogen combinations are obtained by
employing zinc salts.
Sulphide of zinc is changed by cyanide of ammonium producing cyanide of
zinc, cyanide of ammonium, and sulphide of ammonium. From the solution of
the cyanogen double salts cyanide of zinc can be obtained by the addition of
further zinc salts, which cyanide then can be suitably transformed into cyanide
of potassium.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, I declare that what I
claim is:-
1. Obtaining cyanogen combinations from gases containing cyanide of ammo-
nium by treating said gases with a metallic sulphide without the addition of a
fixed alkali substantially as described.
2. Obtaining cyanogen combinations from gases containing cyanide of ammo-
nium or hydrocyanic acid and ammonia by treating said gases with sulphide of
iron or sulphide of zinc substantially as described.
3. The method of obtaining cyanogen combinations from gases containing
cyanide of ammonium or hydrocyanic acid and sulphide of hydrogen and ammo-
nium sulphide consisting in treating said gases with a solution of a metallic sul-
phate such as sulphate of iron to form metallic sulphide and ammonium sulphate,
the cyanide of ammonium contained in the gas then reacting on the metallic
sulphide and forming a corresponding double cyanide of ammonium which passes
into solution substantially as described.
17
1
*ד
1000