IM. PROVEMENTS IN THE SEPARATION OF AMMONIA FROM ILLUMINATING AND OTHER GASES
Year: 1874

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, Gentleman, for the Invention of "IM.
PROVEMENTS IN THE SEPARATION OF AMMONIA FROM ILLUMINATING AND OTHER
GASES." A communication from abroad by Benjamin Silliman, of
New Haven, County of New Haven, and State of Connecticut,
United States of America.
Sealed the 18th September 1874, and dated the 18th July 1874.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson,
at the Office of the Commissioners of Patents, with his Petition
on the 18th July 1874.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE SEPARATIONS OF AMMONIA FROM ILLU-
MINATING AND OTHER GASES," a communication to me from abroad by
Benjamin Silliman, of New Haven, County of New Haven, and State
of Connecticut, United States of America, to be as follows:-
This Invention relates to an improved process for the purification of illu-
minating and of other gases, and consists in the employment of certain
[Price 8d.]

page_text: -
acid salts for the purpose of removing ammonia and other ammoniacal
impurities contained in such illuminating gas or other gases.
"
Invention I take the by-product of acid and
In carrying out this
alkali works known as salt cake," and place it in layers of convenient
thickness in boxes or other form of purifying apparatus familiarly known
to gas engineers, and such as are now in use for what is known as dry
lime purification, or oxide of iron purification, causing the gas as it
comes from the hydraulic main to pass through the apparatus properly
charged with "salt cake" reduced to a suitable degree of fineness; these
agents completely and immediaely remove from the gas or gases all
ammoniacal compounds retaining them in chemical combination in a dry
state, gaining thereby an increased value in proportion to the ammonia
absorbed and combined. As all gas engineers and chemists know the com-
pleteremoval of the ammoniacal compounds from coal gas has presented
hitherto great and insurmountable difficulties involving by the use of
water for this purpose a serious loss of illuminating power in the gas due
to the removal by water of some of its most valuable constituents. By
the use of my Invention this loss is avoided. All, or practically all, the
ammoniacal compounds are withdrawn, the illuminating power of the
gas is increased, and the expense of water which in extensive gas works
is very large is saved to a great extent.
"Salt cake," so called, is a by-product in the manufacture of acdis
and of soda, and varies in composition. That derived from the decomposi
tion of so called South American saltpetre or nitrate of soda by oil of
vitriol, in producing nitric, and also in the production of sulphuric acid
from the excess of that agent used in the process, this is "nitric acid
salt cake." More rarely potassium nitrate is used for the same purpose,
and the "salt cake" from it possesses similar and possibly superior powers
of absorption to that from the sodium nitrate owing to the fact that it is
more completely a bi-sulphate. When common salt or sodium chloride
is decomposed by oil of vitriol, either to produce hydrochloric acid or in
the manufacture of sodium carbonate, the salt cake resulting abounds
in free hydrochloric acid and retains also the excess of oil of vitriol. In
either case the salt cake is an anhydrous body not deliquescent o
hygroscopic, readily reduced to any desired degree of comminution
porous, and in all respects admirably adapted to absorb and retain
ammonia and separate it from its compounds.

page_text: It has discovered and experimentally demonstrated that when a
gas or gases containing ammonia or its compounds are passed over or
through a layer or mass of salt cake properly disposed they part. com-
pletely and at once with all the ammonia therein contained, which
readily combines with the free acid of the salt cake until it is com-
pletely saturated. The separation is so perfect that no trace of ammonia
can be detected by turmeric or litmus paper in the gas after passing the
sub-
salt cake purifiers. The ammonia, thus combined and removed, may
sequently be separated from the salt cake by distillation with the addition
of carbonate or caustic soda, or otherwise, or be otherwise obtained.
Ammonia is produced in other processes of the arts from the decom-
position of organic matters containing nitrogen exhaling odors of a very
offensive nature, of which impure ammonia is one of the most offensive.
By use of my process in connection with any suitable form of condenser
and without water all the ammoniacal compounds may be removed from
such offensive gases, thus abating a nuisance of no small magnitude
now existing in the vacinity of many large towns.
So far as I have been able to discover, my process removes from
illuminating gas when brought in contact with the salt cake, nothing
but the ammoniacal compounds, including carbonate of ammonia and
ammonia sulphide, with a portion of sulpho cyanide of ammonium, and
probably also other compound ammoniums, the nature of which has
But all the ammoniacal compounds
not yet been fully determined.
having been removed the further process of purification of illuminating
gas is simplified and improved, and especially by the absence of any
necessity for washing or scrubbing the gas by the use of water and
ammoniacal liquor, a process which is well understood by all gas
chemists and engineers to be attended with a serious loss of illuminating
power in the gas, while it involves the use of costly apparatus, and as
before-mentioned a large annual outlay for water, producing at the same
time only a partial and imperfect removal of the ammonia, the residual
portion of which goes forward to the consumer of gas, not only
diminishing its light during burning (beyond the loss of power already
experienced from the use of water in scrubbing) but producing also in
its combustion a portion of nitric acid.
In the use of this Invention it is preferred to bring the crude gas into
contact with the bi-sulphate or salt cake before it has passed the
condenser, but this is a point which must be decided in a given case by

page_text: cocal circumstances. If there is a reasonably prolonged flow of the gas
from the hydraulic main of, for example, two or three hundred feet of
large cooling mains, offering a reasonably good opportunity for the deposit
of tar and napthaline, it is better to place the boxes or other form of
apparatus containing the salt cake before the condenser. To avoid the
inconvenience in this case from the deposit of tar with the ammoniacal
compounds the use of a layer of breeze or broken coke before the salt
cake is desirable in a manner familiar to all gas engineers. This breeze
will require to be changed occasionally as it becomes coated to prevent
the arrest of flow in the gas as indicated by the pressure guage.
To use the salt cake it requires to be broken to a coarse powder and
distributed upon trays in the same manner that lime and other purifying
agents are now used. Only that owing to the greater firmness and
porosity of the salt cake it may be safely used in thicker layers than can
be used with lime. The progress and completeness in the process of
removing the ammonia is readily determined by the use of turmeric test
paper, or of neutral litmus paper; the first of which turns from yellow
to brown, and the second from red to blue, as soon as the salt cake is
saturated and the ammonia commences
to pass unabsorbed. The
apparatus must then be changed or recharged in the same manner now
in use in all gas works for lime or oxide of iron purification; care musi
be taken to avoid bringing lime in contact with the salt cake in any
stage of the process, as such contact would be attended with a loss of
ammonia and a frustration of the process.
The power of the salt cake to purify gas from ammonia depends of
course on its degree of acidity, which can be determined beforehand.
Salt cake from the hydrochloric acid process contains usually about
twenty (20°) per cent. of free hydrochloric with some sulphuric acid.
Nitric acid salt cake contains from twelve (12) to fifteen (15) per cent.
of nitric acid, beside the acid sodic sulphate, but these proportions will
vary.
It is in the power of the chemical manufacturer to prepare salt cake
of any desired degree of acidity, either by the use of an excess of oil of
vitriol, forming bi-sulphate of sodium, or potassium, as the case may be,
or by arresting the heat of the furnace at a point which shall leave in
the salt cake the acidity requisite to best fit it for this process. After
the illuminating gas has by this process been freed from its ammoniacal

page_text: impurities it may be passed through any form of condenser which may
be preferred, and then taken to the lime or oxide of iron purifiers for the
removal of the sulphur and carbonic acid in the manner now generally
practised.
It is well known that the spent lime and iron oxide used in the
purification of gas contains a considerable amount of ammonia so com-
bined that immediately on access of air the spent material commences
to heat and then exhales the odor of ammonia, accompanied by offensive
vapors or gases, which together have rendered the exposure of these
effete products a nuisance in large towns. To avoid in part this evil
the ventilation of this spent material is practised in some cases by
causing a current of atmospheric air to pass downward through the
purifying boxes (after the flow of gas has been cut off) induced by a
powerful exhauster with a view to removing this evil. If in such cases
the current of air from such speut material is carried through boxes
charged as I have herein described with salt cake all the ammonia
contained in the spent lime and oxide of iron, which is now a total loss,
will be saved and utilized.
In the destructive distillation of animal matters for producing bone
black and the like, or specifically for the production of ammonia in the
boiling down of animal matters, as in bone boiling and rendering, in the
sweating of hides and other like processes where animal substances are
employed in a greater or less state of putrefaction or chemical change,
ammonia is given off, combined with other offensive vapours or gases.
If these products, which are now a source of great annoyance and injury
to public health are carried by means of a suitable exhauster through
boxes containing salt cake or other acid salts, as herein described, all
the ammoniacal compounds will be combined and removed. For this
purpose it may be found desirable to carry such vapors first through
some suitable dry condenser for the better condensation of aqueous and
other vapors.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent;
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 16th January 1875..
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincolus' Inn Fields, in the County of Middlesex,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighteenth day of July, in the year
of our Lord One thousand eight hundred and seventy-four, in the
38th year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Henry Johnson, Her
special license that I, the said John Henry Johnson, my exe-
cutors, administrators, and assigns, or such others as I, the said John
Henry Johnson my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN THE SEPARATION OF AMMONIA FROM ILLU.
MINATING AND OTHER GASES," a communication to me from abroad by
Benjamin Silliman, of New Haven, and State of Connecticut, United
States of America, upon the condition (amongst others) that I, the said
John Henry Johnson, my executors or administrators, by an instru-
ment in writing under my hand and seal, should particularly describe
and ascertain the nature of the said Invention, and in what: manner
the same was to be performed and cause the same to be filed in the Great
Seal Patent Office, within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the accom-
panying Drawings, and to the letters and figures marked thereon, that
is to say:

page_text: certain acid salts for the purpose of removing ammonia and other
-ammoniacal impurities contained in such illuminating gas or other gases
In carrying out this Invention I take the bye product of acid and
alkali works known as "salt cake," and place it in layers of convenient
thickness in boxes or other form of purifying apparatus familiarly known
to gas engineers, and such as are now in use for what is known as dry
dry lime purification, or oxide of iron purification, causing the gas as it
comes from the hydraulic main to pass through the apparatus properly
charged with salt cake" reduced to a suitable degree of fineness.
These agents completely and immediately remove from the gas or gases
all ammoniacal compounds, retaining them in chemical combination in
a dry state, gaining thereby an increased value in proportion to the
ammonia absorbed and combined. As all gas engineers and chemists
know the complete removal of the ammoniacal compounds from coal
gas has presented hitherto great and insurmountable difficulties, involving
by the use of water for this purpose a serious loss of illuminating power
in the gas, due to the removal by water of some of its most valuable
constituents. By the use of my Invention this loss is avoided. All or
practically all the ammoniacal compounds are withdrawn, the illu-
minating power of the gas is increased and the expence of water, which
in extensive gas works is very large, is saved to a great extent.
"Salt cake" so called is a bye product in the manufacture of acids
and of soda, and varies in composition. That derived from the decom-
position of so called South American saltpetre or nitrate of soda by oil
of vitriol in producing nitric, and also in the production of sulphuric
acid, contains a residue of free nitric acid and of sulphuric acid from the
excess of that agent used in the process. This is nitric acid salt cake,"
more rarely potassium nitrate is used for the same purpose and the
"salt cake" from it possesses similar and possibly superior powers of
absorption to that from the sodium nitrate owing to the fact that it is
more completely a bi-sulphate. When common salt or sodium chloride
is decomposed by oil of vitriol, either to produce hydrochloric acid or in
the manufacture of sodium carbonate, the salt cake resulting abounds in
free hydrochloric acid and retains also the excess of oil of vitriol. [12
either case the salt cake is an anhydrous body, not deliquescent or
hygroscopic, readily reduced to any desired degree of communition,
porous, and in all respects admirably adapted to absorb and retain
ammonia and separate it from its compounds.

page_text: It has been discovered and experimentally demonstrated that when a
gas or gases containing ammonia or its compounds are passed over or
through a layer or mass of salt cake properly disposed, they part com-
pletely and at once with all the ammonia therein contained which
readily combines with the free acid of the salt cake until it is completely
saturated. The separation is so perfect that no trace of ammonia can be
detected by turmeric or litmus paper in the gas after passing the salt
cake purifiers. The ammonia, thus combined and removed, may sub-
sequently be separated from the salt cake by distillation with the
addition of carbonate or caustic soda, or be otherwise obtained.
Ammonia is produced in other processes of the arts from the decom-
position of organic matters containing nitrogen, exhaling odours of a
very offensive nature, of which impure ammonia is one of the most
offensive. By the use of my process in connection with any suitable
form of condenser and without water all the ammoniacal compounds
may be removed from such offensive gases, thus abating a nuisance of
no small magnitude now existing in the vicinity of many large towns.
So far as I have been able to discover my process removes from illu-
minating gas when brought in contact with the salt cake nothing but
the ammoniacal compounds, including, carbonate of ammonia and
ammonia sulphide, with a portion of sulpho cyanide of ammonium, and
probably also other compound ammoniums, the nature of which has not
yet been fully determined. But all the ammoniacal compounds having
been removed the further process of purification of illuminating gas is
simplified and improved, and especially by the absence of any necessity
for washing or scrubbing the gas by the use of water and ammoniacal
liquor, a process which is well understood by all gas chemists and
engineers to be attended with a serious loss of illuminating power in the
gas, while it involves the use of costly apparatus, and as before mentioned
a large annual outlay for water, producing at the same time only a
partial and imperfect removal of the ammonia, the residual portion of
which goes forward to the consumer of gas, not only diminishing its
light during burning (beyond the loss of power already experienced from
the use of water in scrubbing), but producing also in its combustion a
portion of nitric acid.
In the use of this Invention it is preferred to bring the crude gas into
contact with the bi-sulphate or salt cake before it has passed the con-

page_text: denser, but this is a point which must be decided in a given case by local
circumstances. If there is a reasonably prolonged flow of the gas from
the hydraulic main of, for example, two or three hundred feet of large
cooling nains offering a reasonably good opportunity for the deposit of
tar and napthaline, it is better to place the boxes or other form of
apparatus containing the salt cake before the condenser. To avoid the
inconvenience in this case from the deposit of tar with the ammoniacal
compounds, the use of a layer of breeze or broken coke before the salt cake
is desirable in a manner familiar to all gas engineers. This breeze will
require to be changed occasionally as it becomes coated to prevent the
arrest of flow in the gas, as indicated by the pressure guage..
To use the salt cake it requires to be broken to a coarse powder and
distributed upon trays in the same manner that lime and other purifying
agents are now used, only that owing to the greater firmness and
porosity of the salt cake it may be safely used in thicker layers than can
be used with lime. The progress and completeness in the process of
removing the ammonia is readily determined by the use of turmeric test
paper or of neutral litmus paper, the first of which turns from yellow to
brown, and the second from red to blue, as soon as the salt cake is
saturated and the ammonia commences to pass unabsorbed. The
apparatus must then be changed or recharged in the same manner now
in use in all gas works for lime, or oxide of iron purification. Care must
be taken to avoid bringing lime in contact with the salt cake in any
stage of the process, as such contact would be attended with a loss of
ammonia and a frustration of the process.
The power of the salt cake to purify gas from ammonia depends of
course on its degree of acidity which can be determined beforehand.
Salt cake from the hydrochloric acid process contains usually about
twenty (20%) per cent. of free hydrochloric with some sulphuric acid.
Nitric acid salt cake contains from twelve (12) to fifteen (15) per cent.
of nitric acid beside the acid sodic sulphate, but these proportions will
vary.
It is in the power of the chemical manufacturer to prepare salt cake
of any desired degree of acidity, either by the use of an excess of oil of
vitriol forming bi-sulphate of sodium or potassium, as the case may be,
or by arresting the heat of the furnace at a point which shall leave in
the salt cake the acidity requisite to best fit it for this process. After

page_text: the illuminating gas has by this process been freed from its ammoniacal
impurities it may be passed through any form of condenser which may
be preferred and then taken to the lime or oxide of iron purifiers for the
removal of the sulphur and carbonic acid in the manner now generally
practised.
It is well known that the spent lime and iron oxide used in the purifi-
cation of gas contains a considerable amount of ammonia, so combined
that immediately on access of air the spent material commences to heat
and then exhales the odour of ammonia accompanied by offensive vapours
or gases which together have rendered the exposure of these effetc
products a nuisance in large towns. To avoid in part this evil the
ventilation of this spent material is practised in some cases by causing a
current of atmospheric air to pass downward through the purifying
boxes (after the flow of gas has been cut off), induced by a powerful
exhauster with a view to removing this evil. If in such cases the current
of air from such spent material is carried through boxes charged as I
have herein described with salt cake, all the ammonia contained in the
spent lime and oxide of iron which is now a total loss will be saved and
utilized.
In the destructive distillation of animal matters for producing bone
black and the like, or specifically for the production of ammonia in the
boiling down of animal matters, as in bone boiling and rendering, in the
sweating of hides, and other like processes where animal substances are
employed in a greater or less state of putrefraction or chemical change
ammonia is given off combined with other offensive vapours or gases.
If
these products which are now a source of great annoyance and injury to
public health are carried by means of a suitable exhauster through boxes
containing salt cake or other acid salts, as herein described, all the
ammoniacal compounds will be combined and removed. For this
purpose
it may
be found desirable to carry such vapors first through
some suitable dry condenser for the better condensation of aqueous and
other vapors.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same. is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured to
me by the herein-before in part recited Letters Patent is,-

page_text: First. The use of what is known as salt cake or of an alkaline bi-
sulphate or other acid salts for effecting the removal of ammonia and its
compounds from illuminating gas, substantially in the manner herein
described.
Second. The employment of what is known as salt cake for effecting
the removal of ammonia and compounds of ammonia from gases or
vapours derived from the decomposition or from the destructive distillation
of bodies containing nitrogen, as herein referred to.
Third. The employment of what is known as salt cake for effecting
the removal of ammonia or of ammoniacal compounds from the products
of the decomposition of animal matters or from vitiated atmospheres.
Fourth. The employment of what is known as salt cake for the
purpose of arresting and utilizing the ammonia and the ammoniacal
compounds which pass off from the distillation of the spent lime and the
oxide of iron which have been used in the purification of illuminating
gas, substantially as herein described.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal the Fifteenth day of
January, One thousand eight hundred and seventy-five.
J. HENRY JOHNSON. (L.S.)