A CERTAIN NEW AND USEFUL PROCESS FOR OBTAINING FERRO- CYANIDE OF IRON AND AMMONIA FROM THE PRODUCTS OF THE MANUFACTURE " OF COAL GAS
Year: 1882

page_text: LETTERS PATENT to Sydney Pitt of Sutton in the County of Surrey for an
Invention of "A CERTAIN NEW AND USEFUL PROCESS FOR OBTAINING FERRO-
CYANIDE OF IRON AND AMMONIA FROM THE PRODUCTS OF THE MANUFACTURE
"
OF COAL GAS Communicated to him from abroad by Henry Bower of the
City of Philadelphia in the United States of America
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Offico
of the Commissioners of Patents on the 20th June 1882.
SYDNEY PITT of Sutton in the County of Surrey "A CERTAIN NEW AND
USEFUL PROCESS FOR OBTAINING FERROCYANIDE OF IRON AND AMMONIA FROM THE
PRODUCTS OF THE MANUFACTURE OF COAL GAS [Communicated to him from
abroad by Henry Bower of the City of Philadelphia in the United States of
America]
It has long been known in the art that cyanides are produced during the
distillation of coal in the manufacture of gas, and are present in the ammoniacal
liquor resulting from such distillation, and it is the object of this invention to
afford means for extracting ferro cyanide of iron and ammonia from said ammoniacal
liquor in an effective and economical manner. To this end the invention consists
in the addition of iron or a salt of iron to ammoniacal liquor, without, however,
adding acids to said liquor, whereby a considerable portion of the cyanides are
converted into ferro cyanide of ammonia, in such form as to be susceptible of being
thereafter utilized in the manufacture of ammonia and of ferro cyanide of iron
(Prussian blue), by treatment with lime, distillation, and the addition either of
acid and a salt of iron or of an alkali or alkaline salt as hereinafter more fully
set forth.
In the practice of the invention the ammoniacal liquor is submitted as soon as
practicable after its production, to the action of iron, in such form or combination
as will convert the cyanide of ammonium existing in the liquor into ferro-cyanide
of ammonia, it being essential, furthermore, that no acid shall be added at this

page_text: stage. When a soluble salt of iron is employed the amount of cyanide of ammonium
present in the ammoniacal liquor should be ascertained by chemical test, and an
amount of the salt of iron slightly in excess of that called for by equivalents should
be thoroughly stirred in.
If the ammoniacal liquor clear and free from tar, it may be filtered through a
mass of irou borings or turnings, or of sulphide, carbonate, or oxide of iron, so
arranged that the liquor may come in contact with an extended surface thereof.
The action, in this case, will not be as rapid as when a soluble salt is used, but if
the treatment is sufficiently thorough and protracted, an equivalent result will be
effected.
It is essential that the addition of the iron shall be made before the heating
of the liquor for the extraction of the ammonia, and before the addition of any
acid thereto.
If sufficient sulphate of iron be added to the cold gas liquor to decompose all of
the sulphides present in the liquor, the proto or ferrous cyanide of iron will be
thrown out, and remains unchanged on being intimately mixed with the sulphide
of iron which is thrown down; this mixed precipitate, on separation from the liquor,
may be treated with an alkali, or salt thereof, in the usual way to obtain the
cyanides.
The
The cyanide of ammonium originally existing in the ammoniacal liquor having
been converted, as before set forth, into ferro-cyanide of ammonia, the liquor is
treated, for the extraction of the ammonia and ferro cyanide of iron, in one or the other
of the two following ways. In the first method, the liquor, having been run into a
still, lime is added, in the usual proportions, which lime decomposes the ferro
cyanide of ammonia, producing ferro cyanide of calcium and free ammonia.
latter is distilled off, and utilized by any of the methods ordinarily practiced. The
liquor, which now contains ferro cyanide of calcium, in solution, is drawn from the
still, and allowed to stand until the suspended lime and other insoluble matters aro
deposited. The clear liquor is then drawn from the sediment, made slightly acid,
and sulphate or other soluble salt of iron added as long as a precipitate is forined,
by which the ferro cyanide of calcium is decomposed, and ferro cyanide of iron
(Prussian blue) precipitated therefrom.
In the second method, the liquor, after tho addition of the iron or iron salt, as
beforo described, is run into a still or treating vessel, provided with proper means
for agitating its contents, as stirrers or steam jet pipes, lime is added in the usual
proportions requisite to evolve the ammonia, and the latter is distilled off by the
application of heat and agitation. The liquor is then drawn off from the still, and
the settlings or sediment, which contains the desired ferro cyanide, is separated
from the liquor by filtration. Finally, the ferro cyanide is extracted from the
settlings, by heating with an alkaline salt, such as potassium or sodium carbonate,
producing an alkaline ferro cyanide, from which Prussian blue may be precipitated
with an iron salt in the usual manner.
By the hereinbefore described process, the cyanides are obtained from the gas
liquor in such condition as to be readily made merchantable, while the ammonia may
be distilled off and utilized in the ordinary manner. The proportious of salt of iron
and of lime, respectively, which are to be added to the liquor need not be specified
further than has been hereinbefore indicated, as these may be added in excess of
the operative proportions without departing from the spirit of the invention.
It may be found advantageous to perform the first portion of the process at the
gas works, so as to have the ammoniacal liquor acted on by the iron before any
decomposition of the cyanides takes place, as, after they are converted into ferro
cyanides, they become permanent, and the further treatment of the liquor may be
conducted at any convenient place and time.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 20th December
1882.
SYDNEY PITT of Sutton in the County of Surrey. "A CERTAIN NEW AND
USEFUL PROCESS FOR OBTAINING FERROCYANIDE OF IRON AND AMMONIA FROM
THE PRODUCTS OF THE MANUFACTURE OF COAL GAS A communication to me
from abroad by Henry Bower of the City of Philadelphia in the United States of
America.
It has long been known in the art that cyanides are produced during the
distillation of coal in the inanufacture of gas, and are present in the ammonical
liquor resulting from such distillation, and it is the object of this Invention to
afford means for extracting ferro cyanide of iron and ammonia from said ammo-
nical liquor in an effective and economical manner. To this end the Invention
consists in the addition of iron or a salt of iron to ammonical liquor, without
however, adding acids to said liquor, whereby a considerable portion of the
cyanides are converted into ferro-cyanide in such form as to be susceptible of
being thereafter utilized in the manufacture of ammonia and of ferro-cyanido
of iron by treatment with lime, distillation, and the addition either of acid and
a salt of iron, or of an alkali or alkaline salt, as hereinafter more fully set forth.
In the practice of the Invention the aminonical liquor is submitted, as soon as
practicable after its production, to the action of iron, in such form or combination
as will convert the cyanide of ammonium existing in the liquor into ferro cyanide
of ammonia, it being essential, furthermore, that no acid shall be added at this
stage.
It is essential that the addition of the iron shall be made before the heating of
the liquor for the extraction of the ammonia, and before the addition of any acid
thereto.
When a soluble salt of iron is employed, the amount of cyanide of ammonium
present in the ammonical liquor should be ascertained by chemical test and the
necessary amount of the salt of iron called for by equivalent should be intimately
mixed. The ferro-cyanide can then be extracted by one or the other of the two
methods hereinafter mentioned. If by the first method no iron should be
admitted beyond that which combines as ferro-cyanide of ammonium. If there
be more iron the ferro-cyanide is partially or wholly precipitated during the
subsequent operations and is recovered according to the second method.
Or in place of adding a soluble salt of iron the ammonical liquor if clear and
free from tar, may be filtered through a mass of iron borings or turnings, or of
sulphide carbonate, or oxide of iron so arranged that the liquor may come in
contact with an extended surface thereof. The action in this case will not be as
rapid as when a soluble salt is used, but if the treatment is sufficiently thorough
and protracted, an equivalent result will be effected.
The cyanide of ammonium originally existing in the ammonical liquor having
been converted, as before set forth, into ferro cyanide of ammonia, the liquor is
treated, for the extraction of the ammonia and ferro-cyanide, in one or the other
of the two following ways. In the first method the liquor containing only
sufficient iron combined as ferro cyanide, is run into a still, and lime is added, in

page_text: the usual proportions, which lime decomposes the ferro-cyanide of ammonia,
producing ferro-cyanide of calcium and free ammonia. The latter is distilled off
and utilized by any of the methods ordinarily practiced. The liquor which now
contains ferro cyanide of calcium, in solution, is drawn from the still, and allowed
to stand until the suspended lime and other insoluble inatters are deposited. The
clear liquor is then drawn from the sediment neutralized with acid, and sulphate
or other soluble salt of iron added as long as a precipitate is formed by which
the ferro-cyanide of calcium is decomposed and ferro-cyanide of iron precipitate
therefrom.
In the second method, the liquor, after the addition of the iron or iron salt, as
before described but in larger proportion than for the first method is run into a
still or treating vessel, provided with proper means for agitating its contents, as
stirrers or steam jet pipes, lime is added in the usual proportions requisite to
evolve the ammonia, and the latter is distilled off by the application of heat and
agitation. The liquor is then drawn off from the still, and the settlings or sediment,
which contains the desired ferro-cyanide, is separated from the liquor by filtration.
Finally, the ferro cyanide is extracted from the settlings, by heating with a slight
excess of an alkaline salt, such as potassium or sodium carbonate, producing an
alkaline ferro-cyanide, from which ferro cyanide of iron may be precipitated with
an iron salt in the usual manner.
By the herein before described process, the cyanides are obtained from the gas
liquor in such condition as to be readily made merchantable while the amononia
may be distilled off and utilized in the ordinary manner. The proportions of salt
of iron and of lime respectively which are to be added to the liquor, need not be
specified further than has been herein before indicated, as these may be added
in excess of the operative proportions without departing from the spirit of the
invention.
It may be found advantageous to perform the first portion of the process at the
gas works, so as to have the ammonical liquor acted on by the iron before any
decomposition of the cyanides takes place, as after they are converted into ferro-
cyanides, they become permanent and the further treatment of the liquor may be
conducted at any convenient place and time.
It is known that iron has heretofore been added to ammonical liquor in the
presence of a free acid, with the result of producing ferro-cyanide of iron, but, as
in precipitating, the ferro cyanide will be mingled with the tar and other insoluble
impurities of the liquor its separation in marketable condition has been practically
impossible, and further in the presence of free acid, the ammonia could not be
evolved by distillation. It is also known that lime has been used in treating the
spent purifying matters of gas works, and in the ordinary distillation of ammonia
from ammonical liquor. Neither the addition of iron or of lime to ammonical
liquor or other products of the manufacture of coal gas, is herein broadly claimed
as new.
What is claimed as new is.-
First. The process of converting the cyanides of ammonium which are contained
in ammonical gas liquor into ferro cyanides of ammonia, by adding iron, in the
form of a salt, or in the insoluble form of hydrate, carbonate, oxide, or sulphide, or
of metallic iron, and as above specified, to the said liquor, in the absence of acid,
and without neutralizing the ammonia, and before the ammonia is removed
substantially as specified.
Second. The process herein described of treating gas liquor for obtaining
ammonia and ferro-cyanide of iron by first adding iron as specified, to said gas
liquor, thereby producing ferro-cyanide of ammonia then adding lime to free the
ammonia and produce ferro-cyanide of calcium, then distilling off the ammonia,
and finally converting the ferro-cyanide of calcium into ferro-cyanide of iron by
the addition of acid and a salt of iron, substantially as specified.

page_text: Third. The improvement in the process of obtaining ferro cyanides from
ammonical liquor treated with iron and lime as described, which consists in
extracting the ferro-cyanides from the sediment of the liquid by the addition of an
alkali or alkaline salt.
In witness whereof I the said Sydney Pitt have hereunto set my hand and
seal this nineteenth day of December in the year of our Lord Oue
thousand eight hundred and eighty two.