IMPROVEMENTS IN THE MANUFACTURING: OF: GAS FOR THE PURPOSE OF AFFORDING LIGHT
Year: 1838

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
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 Twenty-sixth day of July, in the second year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Alexander Croll, Her especial license, full power,, sole privilege. and authority,
that I, the said Alexander Croll, my exors, admors, and assigns, or. such
others as I, the said Alexander Croll, my exors, admors, 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 MANUFACTURING: OF:
GAS FOR THE PURPOSE OF AFFORDING LIGHT;" in which said Letters Patent is
contained a proviso that I, the said Alexander Croll; shall 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 six calendar months next and immediately after the date
of the said in part 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 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 applies to that part of the manufacture of gas for the purpose
of producing light, which relates to the purifying such gas after it has passed

page_text: from the retorts, from which it is distilled, and the object of my Invention is
to separate the ammonia therefrom more efficiently and with greater advantage
than has been heretofore accomplished; and my Invention consists,―
gas.
First, of a mode of purifying gas by the application of certain salts.
Secondly, of modes of obtaining ammonia from the salts used in purifying
And thirdly, my Invention consists of a mode of purifying gas for the
purposes of light, by the application of oxygen to the sulphuretted hydrogen,
to render it into sulphurous acid, and to decompose the ammonia; and in order
to give the best information in my power, I will proceed to describe the
processes I have pursued in carrying out my Invention.
The manner of applying the salts is as follows:-
I take five hundredweight of nitrate of soda or a similar quantity of nitrate
of potash, and dissolve it in two hundred and fifty gallons of water, which I put
into a cylindrical vessel such as is used in the wet lime purifiers now in use
at gasworks, and are well understood; through this mixture the gas passes by
the pressure from the retorts, and from the influence exerted by the soda on
the sulphuretted hydrogen, and the action of nitric acid on the ammonia, there
are formed by double decomposition hydro-sulphuret of soda and nitrate of
ammonia, and the gas then passes from this process of purification to the
further process of purification by lime as is well understood, and will not
require further description here; the only difference in the ordinary gas
apparatus of a gasworks being the introduction of suitable vessels for the
purifying process by the aid of nitrate of soda or potash, and it should be
stated that it may be desirable to have two or more vessels to contain
the solution of salts above given, in order when the liquor in one has become
saturated, and requires to be drawn, off, the gas may be passed through another,
though this is not absolutely necessary. When the solution has become
saturated, it is to be drawn off; and in order to known whether it is saturated
a piece of litmus paper reddened by an acid is to be opposed to a stream of gas
issuing from a pipe after the gas has passed the vessel; if the gas does not
discharge the acid and return the color to the litmus paper, the solution may
be allowed to remain longer in the vessel until this effect on the litmus paper
be produced, for the ammonia will continue to unite with the acid of the salt
until it be completely decomposed.
The solution is now to be drawn off, the ammonia and sulphuretted hydrogen
are to be expelled, in order to recover the nitrate of soda, to be again used in
the process of purification, which I accomplish by one of the following
processes:-

page_text: First process. I put the liquor obtained as above into a still, which, being
brought up to the boiling point, the soda parts with the sulphuretted hydrogen
and combines with the nitric acid; the ammonia is distilled over with the
sulphuretted hydrogen, which I receive into muriatic or any other acid,
according to the sort of ammonia I desire to obtain, and I pass the vapours
below the surfaces of such acids by a pipe or pipes, the acid used being in any
suitable open vessel, and I chrystallize (to obtain the salts as is well understood),
what remains in the still is nitrate of soda, which, as above-stated, may be,
again and again used.
'
Second process. After the liquor has been fully saturated with the
impurities of the gas (ascertained as before described), and has been drawn off
from the purifyer, supposing nitrate of potash to be the salt, I saturate it with
muriatic or any other acid; the ammonia leaves the nitric acid to combine with
the muriatic or other acid, the nitric acid combines with the potash, and.
sulphuretted hydrogen is evolved, there remains in solution nitrate of potash
and muriate of ammonia, or any other salt of ammonia, according to the
acid used which I separate by chrystallization.
Third process. This I adopt in cases when the salt used may have become
so valueless as not to be worth the labor of reconversion. This process consists
in mixing newly slaked lime with the solution from the purifier in a close
vessel. Heat being applied to this vessel, ammonia is evolved, which I receive
into an open vessel containing muriatic or other acid, in a similar manner to
that already described in the first process.
I will now proceed to describe the third part of my Invention, which consists
in affording to the sulphuretted hydrogen, in the manufacture of gas for the
purpose of light, a sufficient quantity of oxygen either by the use of nitric acid
or otherwise by any convenient means of applying oxygen to this purpose, to
render the sulphuretted hydrogen into sulphurous acid, and also to decompose
the ammonia, as well as to increase the volume of gas. I prefer the use of
nitric acid for this purpose, and I adopt the following process:-I take a portion
of the above acid of the specific gravity of 1.15, diluted with three times its
weight of water; the gas in passing from the retorts is to be exposed to the
action of the acid, in like manner to that pursued for submitting it to the wet"
lime process, as is well understood; for this purpose I employ leaden vessels and
pipes to prevent the prejudicial effects of the acid, and it should be properly
constructed so as to cause the gas to pass intimately in contact with such acid.
The oxygen of the nitric acid having a stronger affinity for the sulphur of the
sulphuretted hydrogen than nitrogen, parts with the latter, and forms
sulphurous acid, this I receive into water by a pipe or pipes passed below the

page_text: surface of water, and any part which may not be absorbed by the water will be
taken up by the usual lime purifiers through which the gas next passes, which
will also purify the gas of the carbonic acid with which it is generally if not
always found contaminated.
Having thus described the nature of my Invention and the manner of
performing the same, I would remark.in regard to the second part of my
Invention that the processes for obtaining the ammonia may be used in the
event of employing other salts than nitrate of soda or potash for purifying the
gas; I do not therefore confine the second part of my Invention to those
cases only where those salts (nitrate of soda and potash) are used, and further
in respect to the Invention generally I would have it understood that I do not
confine myself to any particular construction of vessels as purifiers though I
believe those above directed to be used to be the best and simplest for the
purpose.
And I would have it understood that what I claim as my Invention is,-
First, the mode of purifying gas by the application of nitrate of soda or
potash as above described.
Secondly, I claim the modes of obtaining ammonia, and if desirable, the salts
employed in purifying the gas as 'above explained.
And, thirdly, I claim the mode of purifying gas by the application of
oxygen as herein described.
In witness whereof, I, the said Alexander Croll have hereunto set my
hand and seal, this Twenty-sixth day of January, One thousand
eight hundred and thirty-nine.