Process for Obtaining Yellow Prussiate of Potash as a Bye Product in the Destructive Distillation of Coal.
Year: 1898

page_text: Process for Obtaining Yellow Prussiate of Potash as a Bye Product
in the Destructive Distillation of Coal.
I, WILHELM SCHRÖDER, Colliery Manager, of Wiemelhausen, near Bochum, in the
German Empire, do hereby declare the nature of this invention to be as follows:-
Analyses have shown, that gaseous products of the distillation of coal, after having
been relieved of ammonia, contain per cubic meter of gas 0.7 grammes of prussic
acid (CNH), which quantity, in case it can be utilized for the manufacture of
yellow prussiate, corresponds to 1.82 grammes of crystallized prussiate of potash
(K,Fe(CN), +3 aq.). Consequently, with plant yielding 100,000 cubic ineters of
gas per day, the production of ferro-cyanide would amount to 182 kilogrammes per
day, or 5460 kilos. per month, and the manufacture of prussiate of potash as a bye
product of the destructive distillation of coal, by means of an economical process, is
therefore a great desideratum.
added
The following process has been found to answer this requirement:-
To the water for the absorption of ammonia, protochloride of iron (FeCl2)
before the absorption takes place. When the water takes up ammonia (NH) the
protochloride of iron (F,Cl₂) contained in the water forms with the ammonia ferrous
hydrate Fe(OH)2, besides salammoniac (NHC), with the sulphureted hydrogen
contained in the gas it forms ferrous sulphide (FeS), which together with the ferrous
hydrate mentioned above is held in suspension by the absorption water. At the same
time the prussic acid combines with ammonia to form ammonium cyanide (NHCN),
which then dissolves the suspended ferrous hydrate or ferrous sulphide, thereby
forming aminonium ferro-cyanide. (NH),Fe(C.N).. If now the ammonia is
distilled off as usual with the aid of milk of lime (Ca(OH)2), calcium ferrocyanide
(CaFe(CN)6) remains behind, and as the latter is sparingly soluble, a portion of it
is precipitated.
For recovering the portion which has remained in solution, the gas already relieved
of ammonia and prussic acid is led into the residue (of the distillation) containing the
whole of the lime mud, in order that the carbonic acid contained in the gas may
precipitate the excess of caustic lime in the shape of calcium carbonate (CaCO).
If now a solution of ferric chloride (Fe,Cl) be added, that portion of the calcium
ferrocyanide which has remained in solution separates in the shape of Prussian
blue (2 Fe, 3 Fe(CN)), which rapidly forms a precipitate, together with the entire
lime mud. The whole of the precipitate is then treated with a solution of potassium
carbonate (K.CO3), while boiling and stirring, whereby calcium carbonate (CaCO₂)
and ferric hydrate (Fe(OH),) are precipitated and potassium ferro cyanide
(K4Fe(CN)) enter in solution. The solution thus obtained is boiled down until
crystals of yellow prussiate of potash (K.Fe(CN)6 + 3 aq.) are formed.
Dated this 19th day of September 1898.
FAIRFAX & WETTER,
Agents for the Applicant.

page_text: Process for Obtaining Yellow Prussiate of Potash as a Bye Product
in the Destructive Distillation of Coal.
I, WILHELM SCHRÖDER, Colliery Manager, of Wiemelhausen, near Bochum, in the
German Empire, 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:-
Analyses have shown, that gaseous products of the distillation of coal, after having 5
been relieved of ammonia, contain per cubic meter of gas 0.7 grammes of prussic
acid (CNH), which quantity, in case it can be utilized for the manufacture of yellow
prussiate, corresponds to 1.82 grammes of crystallized prussiate of potash
(K,Fe(CN), +3 aq.). Consequently, with a plant yielding 100,000 cubic meters
of gas per day, the production of ferro cyanide would amount to 182 kilogrammes 1
per day, or 5460 kilos. per month, and the manufacture of prussiate of potash as a
bye product of the destructive distillation of coal, by means of an economical pro-
cess, is therefore a great desideratum.
The following process has been found to answer this requirement :-
:-
To the water for the absorption of ammonia, protochloride of iron (FeCl2) is added 1
before the absorption takes place. When the water takes up ammonia (NH), the
protochloride of iron (FeCl2) contained in the water forms with the ammonia ferrous
hydrate (Fe(OH)2), besides salammoniac (NHCl); with the sulphuretted hydrogen
contained in the gas it forms ferrous sulphide (FeS), which together with the ferrous
hydrate mentioned above is held in suspension by the absorption water. At the same
time the prussic acid combines with ammonia to form ammonium cyanide (NHCN),
which dissolves the suspended ferrous hydrate or ferrous sulphide, thereby forming
ammonium ferro-cyanide. (NH),Fe(CN). If now the ammonia is distilled off, as
usual, with the aid of milk of lime, (('a(OH)2) calcium ferrocyanide (Ca,Fe(CN),)
remains behind, and, as the latter is sparingly soluble, a portion of it is precipi- 2
tated.
For recovering the portion which has remained in solution, the gas already
relieved of ammonia and prussic acid is led into the residue (of the distillation)
containing the whole of the lime mud, in order that the carbonic acid contained
in the gas may precipitate the excess of caustic lime in the shape of calcium 3
carbonate (CaCO₂).
If now a solution of ferric chloride (Fe,Cl) be added, that portion of the calcium
ferrocyanide which has remained in solution, separates in the shape of prussian blue
(2 Fe, 3 Fe(CN)6), which rapidly forms a precipitate, together with the entire lime
mud. The whole of the precipitate is then treated with a solution of potassium 3
carbonate (K,CO), while boiling and stirring, whereby calcium carbonate (CaCO₂)
and ferric hydrate (Fe(OH),) are precipitated and potassium ferrocyanide enters in
solution. The solution thus obtained is boiled down, until crystals of yellow prussiate
of potash (K4Fe(CN), +3 aq.) are formed.
Having now particularly described and ascertained the nature of the said 4
invention and in what manner the same is to be performed I declare that what I
claim is:
contained

page_text: which consists in adding a ferrous salt to the water serving for the absorption of
ammonia, and converting the product into yellow prussiate of potash.
Dated this 10th day of June 1800
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.