A Process for Obtaining Cyanogen or its Compounds from the Gases resulting from the Dry Distillation of Substances of Organic - Origin.
Year: 1894

page_text: Date of Application, 24th Aug.. 1304
Complete Specification Left. 26th Apr.. 1895-Accepted, 15th June, 1895
PROVISIONAL SPECIFICATION.
A Process for Obtaining Cyanogen or its Compounds from the Gases
resulting from the Dry Distillation of Substances of Organic -
Origin.
I, HEINRICH DREHSCHMIDT, of 59, Tannstrasse, Berlin, in the German
Empire, Chemist, do hereby declare the nature of this invention to be as :
follows:-
My invention relates to a process for obtaining on an industrial scale cyanogen
or its compounds from the gases given off in the dry distillation of nitrogenous.
bodies of organic origin, including all kinds of fossil coal, whether pit-coal, lignite
or bituminous shales, turf or wood, and the invention consists essentially in treating
the gas by bringing it into contact with solid and porous mixtures of substances
produced by chemical precipitation, such substances containing approximately from
one or two molecules of the oxide or carbonate of magnesium, calcium or other
alkaline earth metal or metals, in intimate mixture with one molecule of the oxide
or carbonate of one of those heavy metals, such as iron manganese, zinc, etc., which
form with the salts of the former metals, and cyanogen, double compounds not
decomposable by sulphuretted hydrogen and carbonic acid.
.
=
The mixture to be used in the process is prepared in a solid form, and of the
required degree of homogeneity and porosity by precipitating the oxides or
carbonates of the heavy metals referred to from solutions in presence of or
simultaneously with, the oxides or carbonates of the light metals specified. Or by
precipitating the oxides or carbonates of the specified light metals from solutions in.
presence of the oxidės or carbonates of the heavy metals referred to.
Dated this 22nd dex of August. 1891.
COMPLETE, SPECIFICATION..
A Process for Obtaining Cyanogen or its Compounds from the Gases
resulting from the., Dry Distillation of Substances of Organic,
Origin:
I, HEINRICH DREHSCHMIDT, of 59, Tannstrasse, Berlin, in the German,
Empire, Chemist, 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 present invention refers to a process for obtaining on an industrial scale
cyanogen or its compounds from the gases given off in the dry distillation of
nitrogenous bodies of organic origin, including all kinds of fossil coal, whether
pit-coal, lignite or bituminous shales, turf or wood.
It is well known that gas obtained from coal whether in the manufacture of
illuminating gas or coke, contains, after the elimination of the tar. vapors, other.

page_text: impurities, carbonic acid, sulphuretted hydrogen and ammonia, together with a
small amount of cyanogen compounds-(bydrocyanic acid). Gas yielded by turf or
wood contains but little sulphuretted hydrogen and ammonia, but a large quantity of
carbonic acid.
To isolate and recover the cyanogen from such mixtures of gases, the well-known
property of cyanogen, of forming double compounds with the alkalies or alkaline
earths in the presence of a second base has been utilized, and these double salts-are
decomposed with difficulty or not at all by sulphuretted hydrogen or carbonic acid
whilst all simple cyanogeu compounds undergo a more or less easy decomposition
under the action of these two gases. The tendency of cyanogen to form such stable
double compounds is so great that it or its compounds (hydrocyanic acid) acting on
a suitable heavy metal (such as iron, manganese, zinc, etc.) in the form of oxide,
carbonate or sulphide, in the presence of oxide, carbonate or sulphide of potassium,
sodium, ammonium, magesium, calcium, or other alkaline earths, are able actually
to set free carbonic acid or sulphuretted hydrogen, and to form double cyanogen
compounds of a heavy metal and an alkaline metal or alkaline earth.metal. :
Attempts have been made to bring about the formation of such double cyanogen
salts, with a view to the separation and recovery of the cyanogen in the gases of
combustion, by passing the said gases through solutions of the-oxides, carbonates, or.
sulphides, of the alkalies, such solutions containing also the oxides, carbonates,.or
sulphides of the metals referred to, by using a fluid in which with the metallic
compounds alluded to there were present in suspension the, oxides or carbonates of
magnesia, chalk, or other alkaline earths. It was thought to be impossible to
obtain by any other mode of procedure the intimate simultaneous contact of the
cyanogen with the alkali or alkaline earth base, and the metallic base which is
essential to the rapid and certain conversion of the whole of the cyanogen into the
desired stable double cyanogen compound..
In this process however, the disadvantage is experienced that it is difficult to pass
gases through fluids in which solid materials are, and must be, kept in a state of
suspension, and complicated apparatus is necessary to effect it, whilst on the other
hand, gases can be passed with facility through solid materials which are porous
and absorbent, as is done on a large scale in the purification of illuminating gas by
masses of oxide of iron.
It has not hitherto been considered possible, nor has it indeed been possible, to
effect by this method, the dry method, the combination of cyanogen in large
quantity and in a concentrated form. It has been thought that with dry materials,
it only happens to a slight extent that the cyanogen comes into contact with the
metal and the alkali simultaneously and everywhere, and it has been further thought
that when solid materials are employed the cyanogen compounds, as they are
formed, enclose the remaining portions of the mass, and protect it against further
action.
The object of the present invention is to eliminate all the above disadvantages,
and so to effect the isolation and recovery of cyanogen from gases by the use of
solid
porous masses in contrast to the previously used methods consisting in the use
of fluids. To effect this object, the solid materials to be employed must be so
prepared that the gas may obtain access to all parts of the mass at as nearly as
possible the same time, and that the gas shall encounter at all points simultaneously
the compounds of the light and the heavy metals in the proper proportions..
If it were sought to fulfil the required conditions by preparing the mass which is
to form the cyanogen compound by steeping the oxide or carbonate of the metal
with an alkaline solution, it would never be possible for more than a proportionately
small quantity of alkali to be taken up, if the mass be intended to remain solid.
The mass would moreover become hygroscopic, and but slightly penetrable by the
gas. The alkalies alluded to above would therefore, according to the present.
invention, be of necessity excluded when it was desired to form a solid absorption
mass. - But even for the other substances the process of steeping would not be
available; for in the form of their oxides or carbunates they are considerably less

page_text: soluble than the alkalies, if soluble at all indeed, so that the proportion of light
metal taken up by the materials containing the heavy one would be still smaller
than when the alkaline solution was used, nor would a mechanical mixture of the
materials alluded to afford the desired result. Not even as the result of the most
intimate mechanical mixture would the separate particles of the various substances
lie closely together and be evenly distributed to an extent which would secure that
at the same time the cyanogen should come into contact with the various substances
necessary to the formation of a double cyanogen compound in the proportions required.
Moreover, the porosity itself must be of such a kind as to allow the gas to come into
absolute molecular contact with the solid material at all points and to prevent a
protective casing from enclosing considerable portions of the mass, to the exclusion
of further chemical action. This object cannot he attained by any process of
inechanical mixture.
According to the present invention, the isolation and recovery of cyanogen from
gases may be certainly and advantageously effected by bringing the gases in
question into contact with solid materials in which the oxide (anhydrous or in the
form of hydrate or of carbonate) of the light metals referred to above (i.e. metals
of alkaline earths s. a. magnesium, calcium, barium, strontium) are present in the
required-proportion of from one to two molecules, in a mixture with one molecule
of the oxide (anhydrous or in the form of hydrate or of carbonate) of a heavy
metal such as iron, manganese, or the like, which form with the metallic salts
referred to and cyanogen double compounds which are not decomposed by
sulphuretted hydrogen or carbonic acid. The materials alluded to must, however,
be mixed by chemical means, since mechanical methods are useless, so that the
molecular contact may be so intimate, and the porosity so perfect, as to afford the
gas access as complete as possible to every particle of the mixture.
The chemical mixture, which thus brings about the perfect homogeneity of the
material, and the most thorough porosity possible, may be brought by precipitating
the oxides (anhydrous or in the form of their hydrates or carbonates) of the heavy
metals characterized, in the presence of, or in association with, the oxides
(anhydrous or in the form of their hydrates or carbonates) of the light metals
of the alkaline earths, and this may appropriately be effected by means of
the oxides or carbonates of the alkaline or alkaline earth metals. Oxides
(anhydrous or in the form of their hydrates or carbonates) of the aforesaid
light metals may also be precipitated in the presence of oxides or carbonates of the
said heavy metals from their solutions, appropriately by means of oxides or
carbonates of the alkaline metals, so that the precipitation may take place, as it
were, inside the masses of carbonates or oxides of the heavy metals.
The mode of manufacturing the porous mass may be further explained by means
of the following examples.
1. The pulverized oxides (as such or in the form of hydrates or carbonates) of
the light metals of the alkaline earths are suspended in water, and solutions of
such heavy metals as iron, manganese, zinc, or the like, allowed to flow with
constant stirring, the heavy metals being those which in combination with
cyanogen and the light metals mentioned, form double salts which are not capable
of being decomposed by sulphuretted hydrogen or carbonic acid. By the chemical
action of the said oxide of the light metal of the alkaline earth, the said oxides
(ie. as such or in the form of their hydrates or carbonates) of the heavy metals
are precipitated in a state of fine division, and in the most intimate (i.e. molecular)
contact with the portion of the said oxide (or carbonate) of the light metal which
is present in excess of the quantity required to bring about the chemical reaction
referred to.
The proportions present in the mixture may be suitably so adjusted that one
molecule of metal in the oxide (in any specified form) of the heavy metal is
present to one or two molecules or atoms of the oxide (in any specified form) of
the light metal of an alkaline earth. The oxide or carbonate of the light metal
which takes part in the reaction may also be replaced by an equivalent amount of

page_text: a precipitating material which has the same action, as alkali or alkaline carbonate.
The salts of the metals must not be such that the acid they contain unites with
the oxides of the light metals to form insoluble compounds which have no'affinity
for cyanogen e.g. sulphuric acid with oxide of calcium. The precipitate resulting
consisting of the oxides or carbonates of the light and heavy metals, is separated
from the fluid, washed, dried, and powdered.
2. The oxides or carbonates of the light metals aforesaid may also be treated
with a solution of the salts of the heavy metals until as the result the insoluble
mass has the composition already mentioned, in the last paragraph (No. 1). In
this case too, the metallic salt selected must be such a one as was referred to as
regards the acid contained in it, in paragraph No. 1. The resultant mass is then,
as already described, washed, dried, and powdered. The mass described differs
from Laming's mass which latter is only employed for the elimination of
sulphuretted hydrogen from gas, inasmuch as it has a different composition,
containing neither chlorides nor sulphates.
3. A solution containing the salts of the aforesaid light metals, and those of the
heavy metals as well, is allowed to flow into one containing the oxides or carbonates
of the alkalies, or, if magnesium salts be employed, into milk of lime. The. kind
of salt of the heavy metal, the composition of the precipitate, and the further
treatment of the latter, are the same with those described in paragraph No. 1.
4. The oxides (in the specified form such as oxides, hydroxides, carbonates) of
suitable heavy metals may be first of all mixed with a solution of those of the
light metals, of the kind adverted to and then, in order to separate out the oxides
(in the specified form such as oxides, hydroxides, carbonates) of the light metals,
be further treated with a solution of oxide or carbonate of an alkaline metal, the
remaining conditions, and the treatment of the resultant product being as above.
The mass thus obtained, in a state of the greatest attainable freedom from
constituents which have no action upon cyanogen, is so homogeneous, and so
perfectly porous, that the gas is able to act upon every portion of the mass and
finds at the same time, at every point, the proper proportions in the mixture.
The mass is utilized for the absorption and isolation of the cyanogen in a way
- exactly similar to that in which the ordinary gas-purifying materials are made use
of by spreading it out upon wooden hurdles or gratings in cleansing chambers and
passing the gas over and through it. The absorption of the cyanogen is both
rapid and certain, in spite of the fact that both sulphuretted hydrogen and
carbonic acid are present in the gas. If the mass be saturated with cyanogen, or
when the absorption of the same has ceased, the mass is removed and treated in
any way to obtain the cyanogen compounds.
Having now particularly described and ascertained the nature of my-said inveu-
tion and in what manner the same is to be performed, I declare that what I
- claim is :-
1. A process for removing cyanogen from gas, consisting essentially in treating
the gas by bringing it into contact with solid porous mixtures of substances
produced by chemical precipitation, such substances containing approximately
from one to two molecules of the oxide (in the specified form) of metal of alkaline
earths, such as magnesium, calcium, etc., in intimate mixture with one molecule of
the oxide (in the specified form) of one of those heavy metals, such as iron,
manganese, zinc, etc. which form with the salts of the former metals, and cyanogen,
double compounds not decomposable by sulphuretted hydrogen and carbonic acid.
2. The process of preparing a mixture in a solid form, and of the required
degree of homogeneity and porosity to be used for removing cyanogen from gas in
conformity with Claim 1, the said process consisting in precipitating the specified
oxides of the heavy metals herein before described, from sulutions simultaneously
with the specified oxides of the light metals of alkaline earths.
3. A product for use in removing cyanogen from gas in conformity with Claim 1
consisting of a mixture of from one to two molecules of the specified oxides of

page_text: metals of the alkaline earths with about one molecule of the specified oxides of
those heavy metals, e.g. iron, zinc, manganese, etc., which form with cyanogen, in
presence of the metals formerly mentioned, double salts which are not decomposed
by sulphuretted hydrogen and carbonic acid, the said mixture being of so intimate
and porous a character that the gas introduced shall have access to the mixture at
every point and at each point shall encounter at the same time from one to two
molecules of the former oxides (in the specified form) and about one molecule of
the latter oxide (in the specified form) substantially as set forth.
Dated this 26th day of April 1895
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.