Improvements in the Manufacture or Production of Cyanide Compounds from Ferro-cyanide Compounds.
Year: 1890

page_text: Date of Application, 15th Mar., 1890
Complete Specification Left, 1st Apr., 1890-Accepted, 14th June, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Production of Cyanide
Compounds from Ferro-cyanide Compounds.
I, EUGENE BERGMANN, of 31 Johannisbollwerk, Hamburg, German Empire,
Chemist, do hereby declare the nature of this invention to be as follows:-
According to this invention cyanide compounds are produced from ferro-cyanide
compounds by heating in an aqueous solution one molecule of the ferro-cyanide com-
pounds with as many molecules of a silver salt or a copper salt as are necessary to
cause the whole of the cyanogen contained in the ferro-cyanide, to combine with
silver or copper.
I have found that it is essential for the promotion of this reaction, that the mixture
should contain some free acid. This acid has apparently a decomposing action on the
residual ferro-cyanide, prussic acid being produced, which forms with the silver salt
or copper salt present, as the case may be, the very stable cyanide. By the consequent
liberation of fresh quantities of acid, this reaction appears to be repeated until all the
ferro-cyanide is decomposed, or all the copper or silver present has combined with
cyanogen.
The reaction takes place completely; this I have proved not only by weighing the
precipitated copper cyanide or silver cyanide formed but also by quantitative deter-
mination of the iron salt remaining in solution, and resulting from the decomposition
of the ferro-cyanide.
When cupric salts are employed in the production of cyanide of copper, it is
necessary to add a reducing agent to promote the formation of the stable cyanide of
copper.
I have employed with equal success as a reducing agent, sulphurous acid, sulphites,
finely divided metals such for instance as copper cuttings, metallic sulphides, and also
organic compounds.
The following equation illustrates generally the reaction—
6 Ag NO, + K Fe (CN), = 6 Ag CN + 4K NO, + Fe (NU₂),
6 Ag NO, + K. Fe (ON),
=
6 Ag ON + 4K NO, + Fɑ (NU₂),
by which it will be seen that from six molecules of nitrate of silver and one molecule
of ferro-cyanide of potassium, there are formed six molecules of cyanide of silver,
four molecules of nitrate of potassium and one molecule of nitrate of iron.
In carrying out the process I dissolve 422 parts by weight (1 molecule) of
crystallized ferro-cyanide of potassium in fifty times its weight of water, and mix
therewith a two per cent. aqueous solution containing 1020 parts by weight
(6 molecules) of silver nitrate. After acidifying with sulphuric acid, heat is applied
until the precipitate of ferro-cyanide of silver first formed is converted into cyanide
of silver by taking up the surplus silver salt remaining in solution. The soluble
potassium and iron salts are separated from the insoluble cyanide of silver by
decantation and washing with water.
When a cupric salt, for example sulphate of copper, ferro-cyanide of potassium and
sulphurous acid are employed, the reaction is as follows :—

page_text: copper formed, the operation should be effected either in a considerably diluted
solution, or the greater part of the free sulphuric acid should be neutralized by the
addition of alkali; unless it be preferred to employ a sulphite of copper at the
beginning instead of a sulphate.
Besides the whole of the soluble ferro-cyanide compounds, there may be employed
in the processes herein before described those ferro-cyanides that are insoluble, such
for instance as Prussian blue, and also such as are obtained in the raw state from spent
gas purifying material, and even ferro-cyanide compounds in the presence of a
reducing body.
It will be understood that copper salts, such for instance as cuprous chloride, can
also be transformed according to my invention into cyanide of copper as also can the
cupro ferro cyanide hereinafter referred to and obtained as an intermediate product
by my process.
When employing the said capro-ferro-cyanide with cuprous chloride the reaction is
Ung (UN), Ba (ON), + K, SO, = Ba SO, + Cu, (CN), 2 K ON.
Copper cyanide double salts of other combinations than those herein before
mentioned, can be obtained by varying the quantity of the metallic sulphide added.
Thus a double salt that has a chemical action different to that of the potassium copper
cyanide, above referred to, is produced by boiling three molecules of cyanide of
copper with one molecule of ferro-cyanide of potassium in aqueous solution until a
sample when taken out, filtered, and acidulated ceases to give any ferro-cyanide
reaction with iron chloride. The reaction takes place according to the following
equation :-

page_text: The precipitate of cupro-ferro-cyanide when boiled as before described with cuprous
chloride will again produce cyanide of copper, which after the soluble chloride of iron
has been washed out, can be used again for the production of double salts.
Dated this 15th day of March 1800
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture or Production of Cyanide
Compounds from Ferro-cyanide Compounds.
I, EUGENE BERGMANN, of 31 Johannisbollwork, Hamburg, German Empire,
Chemist, do hereby declare the nature of this invention and in what manner the
saine is to bo performed to be particularly described and ascertained in and by the
following statement :—
According to this invention cyanide compounds are produced from ferro-cyanide
compounds by heating in an aqueous solution one molecule of a ferro-cyanide
compound with as many molecules of a silver salt or a copper salt as are necessary to
cause the whole of the cyanogen contained in the ferro-cyanide, to combine with the
silver or copper.
I have found that it is essential for the promotion of this reaction, that the mixture
should contain some free acid. This acid has apparently a decomposing action on the
ferro-cyanide, prussic acid being produced, which forms with the silver salt or copper
salt present, as the case may be, a very staple cyanide. By the consequent liberation
of fresh quantities of acid, this reaction appears to be repeated until all the
forro-cyanide is decomposed, or all the copper or silver present has combined with
cyanogen.
The reaction takes place completely; this I have proved not only by weighing the
precipitated copper cyanide or silver cyanide formed, but also by quantitative
determination of the iron salt remaining in solution, and resulting from the decom-
position of the ferro-cyanide.
When cupric salts are employed in the production of cyanide of copper, it is
necessary to add a reducing agent to promote the formation of the stable cyanide
of copper.
I have employed with equal success as a reducing agent, sulphurous acid, sulphites,
finely divided metals such for instance as copper cuttings, metallic sulphides, and also
organic compounds.
The following equation illustrates generally the reaction―
6 Ag NO, + K, Fe (ON). = 6 Ag CN + 4K NO, + Fe (NOS),
by which it will be seen that from six molecules of nitrate of silver and one molecule
of ferro-cyanide of potassium, there are formed six molecules of cyanide of silver, four
molecules of nitrate of potassium and one molecule of nitrate of iron.
In carrying out the process I dissolve 422 parts by weight (1 molecule) of
crystallized ferro-cyanide of potassium in fifty times its weight of water, and mix
therewith a two per cent. aqueous solution containing 1020 parts by weight (6 mole-
cules) of silver nitrate. After acidifying with sulphuric acid, heat is applied until
the precipitate of ferro-cyanide of silver first formed is converted into cyanide of
silver by taking up the surplus silver salt remaining in solution. The soluble potassium
and iron salts are separated from the insoluble cyanide of silver by decantation and
washing with water.
When a cupric salt, for example sulphate of copper, ferro-cyanide of potassium and
sulphurous acid are employed, the reaction is as follows :-
6 Ag NO,
K. Fe (CN),
=
6 Ag CN + 4K NO, + Fe (NOS),
by which it will be seen that from six molecules of nitrate of silver and one molecule
of ferro-cyanide of potassium, there are formed six molecules of cyanide of silver, four
molecules of nitrate of potassium and one molecule of nitrate of iron.
In carrying out the process I dissolve 422 parts by weight (1 molecule) of
crystallized ferro-cyanide of potassium in fifty times its weight of water, and mix
therewith a two per cent. aqueous solution containing 1020 parts by weight (6 mole-
cules) of silver nitrate. After acidifying with sulphuric acid, heat is applied until
the precipitate of ferro-cyanide of silver first formed is converted into cyanide of
silver by taking up the surplus silver salt remaining in solution. The soluble potassium
and iron salts are separated from the insoluble cyanide of silver by decantation and
washing with water.
When a cupric salt, for example sulphate of copper, ferro-cyanide of potassium and
sulphurous acid are employed, the reaction is as follows:-

page_text: The precipitate of cupro-ferro-cyanide when boiled as before described with
cuprous chloride will again produce cyanide of copper, which after the soluble
chloride of iron has been washed out, can be used again for the production of
double salts.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The production of cyanide compounds from ferro-cyanide compounds, by heating
either in neutral aqueous solution or in the presence of a free acid a ferro-cyanide
compound and a silver salt or a copper salt, in substantially the proportions indicated,
the number of molecules of the silver salt or copper salt to each molecule of the
ferro-cyanide compound being such as to cause the whole of the cyanogen contained
in the ferro-cyanide to combine with the silver or copper and the process being,
when cupric salts are employed, effected in the presence of a reducing agent.
2. The production of double salts of evanide of copper by treating cyanide of copper
with the sulphide of an alkaline metal or of an alkaline earthy metal, or with an
alkaline ferro-cyanide.
3. The production of mixtures or double salts of cyanide of copper with cyanides of
other metals by treating barium copper cyanide obtained by the process referred to
in claim 2, with a sulphate or carbonate in an aqueous solution substantially as herein
described.
Dated thin 1-2 1-
A
1000
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.