IMPROVEMENTS IN THE MANUFACTURE OF GAS, AND IN CONVERTING THE SALTS USED IN PURIFYING GAS, AND IMPROVEMENTS IN THE MANUFACTURE OF AMMO- NIACAL SALTS
Year: 1839

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, of Greenwich, in the County of Kent, Manufacturing Chemist,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Second day of November, in the third year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Alexander Angus Croll, the especial licence, full power, and sole privilege and
authority, that I, the said Alexander Angus Croll, my executors, administrators,
and assigns, or such others as I, the said Alexander Angus Croll, my exe-
cutors, administrators, or assigns, should at any time agree with, and no
others, from time to time and at all times during the term of years therein
expressed, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, my Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF GAS, AND IN CONVERTING THE SALTS
USED IN PURIFYING GAS, AND IMPROVEMENTS IN THE MANUFACTURE OF AMMO-
NIACAL SALTS;" in which said Letters Patent is contained a proviso that I,
the said Alexander Angus Croll, shall cause a particular description of the
nature of my said Invention, and in what manner the same is to be per-
formed, to be enrolled in Her said Majesty's High Court of Chancery within
six calendar months next and immediately after the date of the said in part

page_text: recited Letters Patent, as in 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 the nature of my said Invention,
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, the application of the coke taken from the retorts when they are
drawn while hot as fuel, in order to obtain the required heat in the furnaces
to generate the gas, by which a considerable portion of the fuel will be saved.
Secondly, in the methods of purifying coal gas from ammonia, by the appli-
cation of certain salts and carbonic acid, herein-after described.
Thirdly, in the obtaining of ammoniacal salts by means of the salts used in
the purification of the gas.
Fourthly, in the methods of reconverting or reproducing the salts used in
the purification of the gas that they may be used or employed again for the
same purpose.
.
And in order to give the best information in my power, I will proceed to
describe the process to be pursued in carrying out my said Invention.
Firstly, in order to apply the hot coke obtained from the retorts when
drawn as before mentioned, I adopt an iron carriage on wheels; and to direct
the course of the carriage in front of the furnaces I construct an iron rail, for
the wheels to run upon. This carriage is placed in front of the retorts that
require to be drawn, and a suitable quantity of coke for feeding the furnaces
is drawn into the carriage, and while the heat remains in the coke it is, taken
towards such of the furnaces as require, a charge of fuel, and, the coke in.
this hot state is thrown into the furnaces.
Secondly, the manner of employing the salts is as follows:-A, vessel.such
as is now used in the purification of coal gas with wet lime should be charged.
with a solution in the proportion of one hundredweight, of chloride of zinc,.
or thereabouts, to forty gallons of water, in the same manner as if wet lime
were used, and which is well understood. The gas is to be transmitted,
through this solution by means of the pressure from the retorts. This salt has.
the effect of freeing the coal gas from the whole of the ammonia which it
contained, and from part of its sulphuretted hydrogen. It is proper to state;
that after the gas has been submitted to this process it will in general re-
quire a further purification in order to free it from the remaining portion of
sulphuretted hydrogen, which is to be effected in the ordinary way by the
use of lime. The solution of the chloride of zinc is to be withdrawn when.
saturated with ammonia, which saturation may be observed by means of:a

page_text: piece of litmus paper reddened by an acid, or by any other well-known means or
test, which paper is to be exposed to a stream of gas issuing from an aperture
in the pipe after it has passed through the vessel or vessels containing the
solution of chloride of zinc. If the gas does not change the red colour of
the litmus paper or other test to blue, the solution may be allowed to remain
longer until this effect on the litmus paper or other test be produced.
Having thus fully described the process employed by me for freeing coal gas
of ammonia by means of chloride of zinc, I now state that certain other salts
may be substituted for the same purpose for the chloride of zine, to wit,
sulphate of zinc, chloride of magnesium, otherwise called muriate of magnesia,
sulphate of magnesia, chloride of calcium, otherwise called muriate of lime,
chloride of barium, otherwise called muriate of barytes, and the preferable use
of any one of them being determined by their relative prices, and by other cir-
cumstances. In some cases more than one vessel with the salts for purifica-
tion may be desireable, especially where the gaswork is very extensive, and
a different salt may be used in each vessel. The sulphate of lime may be
applied in the dry state, that is, in the same condition as hydrate of lime is
employed in dry lime purifyers, instead of being dissolved or diffused through
water as described above. For the proper and most effectual use of all theso
salts, and in order to obtain the largest product of ammonia, they must be
applied to the gas after it has passed through the ordinary condensing appa-
ratus, but before it has been transmitted through any lime purifyers. When
the salts of lime, magnesia, or barytes are used, I also add a portion of carbonic
acid gas to the coal gas before it is passed through these solutions. The carbonic
aeid thus added causes the ammonia in the coal gas to be more completely
withdrawn from it by salts of lime, magnesia, or barites, carbonate of lime,
carbonate of magnesia, carbonate of barytes being then formed and obtained
as the insoluble matter, while the salt of ammonia formed remains in solution.
The supply of carbonic acid gas required for this purpose may be obtained by
dissolving chalk in muriatic acid, or by any other means by which it can be
economically obtained. The quantity which is added to the coal gas may be
regulated by passing it through a metre, or by any other ordinary methods of
measuring gases. The portion of carbonic acid gas thus introduced need not
be greater than is sufficient to convert the estimated quantity of ammonia iu.
the coal gas into carbonate of ammonia.
Thirdly, my mode of obtaining the ammoniacal salts from any of the solu-
tions described above is as follows:-I take the liquor when saturated with
ammonia and place it in a suitable vessel to allow the insoluble matter to
settle. I then draw off the clear liquor which contains the salt of ammonia

page_text: and obtain that salt by evaporation, either to the point of chrystilization or to
dryness.
Fourthly, the insoluble matter above mentioned is then to be reconverted
into the original salt, by dissolving it in the neid formerly combined with its
base, or it may be dissolved in either muriatic or sulphuric acid, as it should
be desired, to form sulphate or muriate of ammonia in any subsequent opera-
tion, and the salt thus formed may be again used in freeing the gas from
ammonia. It will be easily perceived that the particular form of the vessel
for purifying the gas is not material, so that it contain a sufficient quantity of
the purifying material be supplied, according to the principles of purification
well known, and one or more vessels may be used for that purpose; and
I therefore do not claim any particular form of apparatus or utensil. But I
claim the purification of coal gas by means of the salts and carbonic acid
herein-before mentioned, in the manner herein-before described, except that I
do not claim the use of the salts of lime, unless it be after an additional
quantity of carbonic acid gas is added to the gas, whereby the gas will be
entirely deprived of its ammonia, and a valuable product thereby obtained.
I also claim the forming of the ammoniacal salts as herein-before described,
and also the conversion of the basis, that is to say, the oxide of zinc, tho
lime or magnesia, or the carbonates or bydro-sulphuret, or the mixture of
carbonates and hydro-sulphuret of either zinc, lime, magnesia, or barytes
that is or may be formed in the above process of purification into either
sulphates or chlorides, otherwise called muriates of either zinc, lime, or
magnesia, in order that they may be repeatedly applied and effect the same
object. And lastly, I claim, as part of my Invention, in order to effect an
economy in the fuel used for carbonizing the coal in the retorts, the employ-
ment of the hot coke, as herein-before described; but I do not claim any
particular mode of conveying the said hot coke to the furnaces.
In witness whereof, I, the said Alexander Angus Croll, have hereunto
set my hand and seal, this Second day of May, in the year of our
Lord One thousand eight hundred and forty.
ALEXANDER (L.S.) ANGUS CROLL.
Signed, sealed, and delivered by the
within-named Alexander Angus

page_text: AND BE IT REMEMBERED, that on the same Second day of May, 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.
Inrolled the Second day of May, in the year above written.