CERTAIN IMPROVEMENTS IN THE MANUFACTURE OF GAS FOR THE PURPOSE OF ILLUMINATION, AND FOR THE PREPARATION OR MANUFACTURE OF MATERIALS TO BE USED IN THE PURIFICATION OP GAS FOR THE PURPOSE OF ILLUMINATION
Year: 1840

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, Superintendent of the Works of the Gas Light and Coke
Company, in Brick Lane, in the County of Middlesex, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Iler
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-ninth day of July, in the fourth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said
Alexander Angus Croll, Her special license, full power, sole privilege and
authority, that I, the said Alexander Angus Croll, my executors, administrators,
or assigns, and every of them, by myself and themselves, and by my and their
deputy or deputies, servants or agents, or such others as I, the said Alexander
Angus Croll, my executors, administrators, or assigns, should at any time
agree with, and no others, from time to time and at all times during the term
of fourteen years from the date of the said Letters Patent, should and lawfully
might make, use, exercise, and vend, within that part of the United Kingdom
of Great Britain and Ireland called England, and the Dominion of Wales, and
the Town of Berwick-upon-Tweed, my Invention of "CERTAIN IMPROVEMENTS
IN THE MANUFACTURE OF GAS FOR THE PURPOSE OF ILLUMINATION, AND FOR THE
PREPARATION OR MANUFACTURE OF MATERIALS TO BE USED IN THE PURIFICATION
OP GAS FOR THE PURPOSE OF ILLUMINATION;" in which said Letters Patent is
contained a proviso, that I, the said Alexander Angus Croll, should cause a
particular description of the nature of my said Invention, and in what
manner the same is to be performed, to be inrolled in Her said Majesty's
High Court of Chancery within four calendar months next and immediately

page_text: after the date of the said part recited Letters atent, as m and by the
same, reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Alexander Angus Croll, do hereby declare that the nature of my said Inven-
tion, and the manner in which the same is to be performed, are fully described
and ascertained in and by the following statement thereof, that is to say :-
My Invention consists, first, in the methods of purifying coal gas from
ammonia by the application of certain salts, acids, and oxides herein-after
described.
Secondly, in a peculiar method of reconverting or manufacturing of the salts
used in the purification of the gas, that they may be used repeatedly for the
same purpose.
gas
First, the manner of employing the salts in the purification of coal gas is as
follows: A vessel such as is now used in the purification of gas with wet lime,
commonly called cream of lime, should be charged with a solution in the
proportion of one hundredweight of chloride of manganese, or thereabouts, to
forty gallons of water, in the same manner as if wet lime were used, and is
well understood. The gas is to be passed through this solution by means of
the pressure from the retorts in the same way as through wet lime, by which
operation the gas will be freed from the ammonia which it contains, and part
of the sulphuretted hydrogen. It is proper here to state, that after the has
been submitted to this process, it should have a further purification in order to
free it from the remaining portion of sulphuretted hydrogen, which purification
is to be effected by means of the oxides herein-after described, or in the ordinary
way by the use of lime. The solution of the chloride of manganese is to be
immediately withdrawn from the vessel when saturated with ammonia, which
saturation may be ascertained by means of a piece of litmus paper reddened
by an acid or by any other well-known test, which paper is to be exposed to a
stream of gass issuing from an aperture in a pipe after it has passed from the
vessel or vessels containing the chloride of manganese; if the gas do not change
the red color of the litmus paper to its original tint, the solution may be allowed
to remain longer, until this effect upon the litmus paper be produced; the
change in the red tint indicating the saturation of the solution.
Secondly, the same results of freeing coal gas from ammonia, may be
accomplished by the use of sulphuric and muriatic acids, as follows:-If
sulphuric acid be employed, a vessel similar to that one now used in the
washing of coal gas is to be charged with water and sulphuric acid in the
proportion of one hundred gallons of water to two and a half pounds of
sulphuric acid, commonly called oil of vitriol, of the specific gravity gravity of

page_text: 1.845, and this mixture is to have the gas passed through it in a similar way to
that now in use in the process of washing, testing the solution of the acid mix-
ture by litmus paper reddened with acid in the same manner as in the process
already described. When found saturated by the change in the color of the
litmus paper, a further quantity of acid must be put into the washing vessel;
and in order to prevent any deterioration in the illuminating power of the gas
by diminishing the quantity of carbon in the gas, which might be the case
with gas of very high specific gravity were too great a strength of acid
employed, I recommend the further supply of acid by means of a reservoir of
acid placed above the washing vessel, from which a small tube descends over
the mouth of a funnel, and the acid be allowed to drop or run in a small
stream into this funnel, which funnel communicates with the washing vessel
by means of a small tube descending to the bottom of the vessel, and turned
up again for about four or five inches, terminating with a flanch for dispersing
the acid. The quantity of acid dropping or running from this reservoir can
be easily regulated by drawing off a pint of the liquor, and adding
to it one-sixteenth of an ounce of sesqui-carbonate of ammonia, testing
this mixture with a reddened litmus paper, as already described; and if
the color of the test be changed, the stream of the acid into the washing
vessel should be increased; but should the color remain unchanged, the
stream of acid should be somewhat lessened; this process of passing the
gas through this liquor, must be continued until the liquor in the washing
vessel arrives at the specific gravity of 1170, to be ascertained by a hydro-
metre in the usual way, when the supply of acid to the washing vessel is to be
stopped, and the liquor retained until the whole of the acid is absorbed by the
ammonia, or until no free acid remains, to be ascertained by litmus paper,
as before described, after which the liquor is to be withdrawn and evaporated*
in the ordinary way to obtain the sulphate of ammonia which it contains;
the washing vessel may then be recharged, as in the first instance, and the
operation repeated. It is necessary to state that the washing vessel in this
process should be lined with lead, that vessel not being acted upon by sulphuric
acid; muriatic may be employed in the same manner; as to proportion, its.
specific gravity being 1165 before mixed with water for extracting the
ammonia from coal gas, and removed when the liquor is found of the specific
gravity of 1170, as in the case of sulphuric acid, but I prefer sulphuric acid.
Certain other salts may be used for the same process, as sulphate of manganese
and muriate of iron. In some cases more than one vessel with the salts or
acids may be desirable when the gas works are very extensive, and for the
proper and most effectual use of these salts and acids, but especially for the

page_text: effectual use of the salts, and in order to obtain the largest product of ammonia
from the gas, my process of extracting ammonia must be used after the gas
has passed the ordinary condensing apparatus, but before the gas has been
deprived of its sulphuretted hydrogen by means of the oxides to be herein-
after described, or by the ordinary use of lime. To obtain the ammoniacal
salts (when a salt has been used for purification), allow the insoluble matter
to settle, then draw off the clear liquor, which contains the salt of ammonia,
and obtain that salt by evaporation in the ordinary way. If from an acid, it
is only necessary to evaporate the salt of ammonia, the insoluble matter as
above mentioned, as produced from the use of the salts, may be reconverted
into its original state by dissolving it in the acid formerly combined with its
base, or it may be dissolved in either sulphuric or muriatic acid, as it should be
desired to form a sulphate or muriate of ammonia in any subsequent operation,
and the salts thus formed may be again and again used for freeing the gas from
ammonia.
The third part of my improvements in the manufacturing of coal gas consists
in the application of the black oxide of manganese to remove or free coal gas
of sulphuretted hydrogen, which is accomplished in the following manner:
After the gas has been freed from animonia as above described, it is then to be
passed through a vessel similar to those now in use for the purification of coal
gas by what is denominated dry lime, and charged in a similar manner with
black oxide of manganese in powder, moistened with water to about the same
consistency. The period required for each charge is to be ascertained and
regulated by the same tests as if dry lime were used, and which is well under-
stood, in short, requiring no further alterations, except in the materials I
employ for the absorption of the sulphuretted hydrogen. This material, after
it has ceased to absorb the sulphuretted hydrogen, is to be removed from the
purifying vessel, and roasted in an oven to expel the sulphur which it then
contains. After this material has become thoroughly red in the oven, I have
found from two to three hours further time to be sufficient to accomplish this
object, taking care that whilst it is being roasted it be well stirred about in the
oven. After this operation is completed the material is fit again to be
employed, by being placed in the purifier moistened with water, as in the first
instance. The same effect may be produced by the application of the oxide of
zinc and the oxides of iron, and treated precisely in the same way as above
described.
Secondly, my peculiar mode of manufacturing, or preparing, or repro-
ducing the salts for the purification of coal gas is by double decomposition
with common salt, and the precipitate and the residuum that is thrown down

page_text: from the chloride of manganese in the following manner:-For every twelve
ounces of the dry precipitate take one pound of common salt, or thereabouts,
and after mixing them well together, expose them for two or three hours in a
heat scarcely visible in the dark, in any suitable furnace, care being taken that
the heat be not increased beyond this degree, nor the materials exposed too
long to this heat, which would be indicated by the formation of a green color,
or of a brown color. In case salts of a zinc were used, the mixture having
by the effect of the heat become light and spongy, it is to be removed from
the furnace and dissolved in water in the proportion of one hundred and forty
pounds to every forty gallons of water, and this mixture forms the solution to
be placed in the purifier for the further purification of the gas from ammonia,
as previously described in the employment of chloride of manganese. The
gas in passing through this solution forms a precipitate, which is to be again
treated with common salt, as in the manner above described. The liquor
drawn off from the residuum in this my peculiar process, being muriate of
ammonia and sulphate and sulphate of sodium, are to be separated from each
other, either by crystallizing the ammonia out of the salts of sodium, or by
evaporating both to dryness, and subliming the muriate of ammonia from
the salts of sodium, the latter being left in the subliming pot, which process
is well known and understood. The precipitates formed in using any of the
salts of manganese and iron, above mentioned, or any of the salts of zinc
(when zine is used, as previously patented by me), may be reformed in like
manner. In my peculiar process, above described, it will be easily seen that
the form of the vessels for the purification of the gas from ammonia is not
material. The form I prefer for the salts is a vessel similar to the wet limo
purifyer in common use, and that for the acids similar to the washing vessels
also in common use in coal gas works, only in the latter case it is desirable
that the vessels be lined with lead, as already observed. I, therefore, do not
claim any particular form of vessel or utensil for this purpose; but I claim
the purification of coal gas from ammonia by means of chloride and sulphate of
manganese, and muriate of iron, and sulphuric and muriatic acids, and the
purification of gas from sulphuretted hydrogen by means of the oxide of man-
ganese, the oxides of iron, and the oxide of zinc, as hercin-before mentioned and
herein-before described, as applied in the particular manner and stage of the
process of the manufacturing of coal gas, herein-before mentioned, and not
otherwise.
I also claim the peculiar mode of manufacturing or reforming all the salts
by double decomposition, as herein-before described; and such my Invention
being to the best of my knowledge and belief entirely new, and never before

page_text: used in that part of Her Majesty's United Kingdom of Great Britain and
Ireland called England, Her Dominion of Wales, and Town of Berwick-upon-
Tweed, I do hereby declare this to be my Specification of my said Invention,
and that I do verily believe this my said Specification doth comply in all
respects fully and without disguise with the proviso in the said herein-before in
part recited Letters Patent contained, wherefore, I do hereby claim to main-
tain exclusive right and privilege to my said Invention.
In witness whereof, I have hereunto set my hand and seal, this Twenty-
eighth day of November, in the year of our Lord One thousand eight
hundred and fortr
Signed, sealed, and delivered by the within-named
Alexander Angus Croll, in the presence of
WILLIAM PRUDENCE,
6, Basinghall Street.
AND BE IT REMEMBERED, that on the same Twenty-eighth day of
November, in the year above mentioned, the aforesaid Alexander Angus
Croll came before our Lady the Queen in Her Chancery, and acknowledged
the Specification aforesaid, and all and every thing therein contained, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute in that case made and provided.