IMPROVEMENTS IN PURIFYING GAS FOR ILLUMINATION, AND OBTAINING A VALUABLE PRODUCT IN THE PROCESS
Year: 1845

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANK
HILLS, of Deptford, in the County of Kent, Manufacturing Chemist, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Ninth day of August, in the ninth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Frank Hills, my exors, admors, and assigns, Her especial licence, full power,
sole privileges and authority, that I, the said Frank Hills, my exors, admors,
and assigns, or such others as I, the said Frank Hills, 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
PURIFYING GAS FOR ILLUMINATION, AND OBTAINING A VALUABLE PRODUCT IN THE
PROCESS;" in which said Letters Patent is contained a proviso that I, the
said Frank Hills, 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
Frank Hills, have ascertained and set forth the nature of my Invention, and

page_text: the manner in which the same is to be carried into effect, in and by the
following description thereof, and by the Drawings hereunto annexed (that is
to say):-
My Invention consists of several new modes or processes for purifying gas
for the purpose of illumination by freeing it from the ammonia and its com-
binations which are mixed with it, and for obtaining as a product ammonia
or its compounds, which processes may be employed in conjunction with any
of the ordinary processes for freeing the gas from the sulphuretted hydrogen
combined with it.
My first improvement consists of a mode or process for effecting these
objects by passing the gas through a solution of sulphate or muriate of mag-
nesia contained in a vessel similar to what is commonly called a whet lime
purifier, having a stirrer or agitator. The solution of sulphate or muriate of
magnesia may be of the specific gravity of 1.150 to 1.200.
In the passage
of gas through the purifier the carbonate of ammonia contained in the gas
and some free ammonia combine with the acid of the magnesian salts, decom-
posing them and forming muriate or sulphate of ammonia in solution, and
precipitating magnesia and carbonate of magnesia.
I claim under this head of my Invention the purifying of gas by passing it
through a solution of sulphate or muriate of magnesia.
My second mode or process consists in the employment of sulphate of lime
(preferably precipitated) in lieu of the salts of magnesia mentioned in my
first process.
This salt is introduced into the purifier before described mixed
with water to the consistence of cream when stirred up, and the gas is passed
through it in the usual way; a portion of the salt is dissolved by the water,
and is then decomposed by the carbonate of ammonia in combination with the
gas in the passage of the gas through the solution, whereby sulphate of
ammonia in solution is formed and a precipitate of carbonate of lime. As the
carbonate of lime is precipitated more sulphate of lime becomes dissolved,
which again becomes decomposed, and sulphate of ammonia and carbonate of
lime are formed in a continuous process until the whole of the sulphate of
lime is decomposed; more sulphate of lime may then be introduced into the
purifyer before the charge is drawn off, and be decomposed like the former, so
as to obtain a strong solution of sulphate of ammonia: the whole contents of
the purifyer must then be drawn off, consisting of sulphate of ammonia in
solution, which may be evaporated and chrystalized, and a precipitate of
carbonate of lime, which may be thrown away or it may be reconverted into
sulphate of lime by the addition of the requisite quantity of sulphuric acid

page_text: and be used again. A fresh charge may then be introduced, and the process
continued as before.
I claim under this head of my Invention the purifying of gas by passing it
through sulphate of lime and water.
My third improved mode or process consists in employing the bisulphates or
supersulphates and sesquisulphates of soda and potash in solution as the purify-
ing materials. They may be introduced into the purifyer and mixed with water
in the proportion of six or eight pounds of the dry bisulphates to a gallon of
water. In the passage of the gas through this solution the ammonia, car-
bonate of ammonia, and hydrosulphuret of ammonia which are combined
with the gas unite with one equivalent of the acid of the bisulphates, forming
sulphate of ammonia. To ascertain when the solution of the bisulphate has
ceased to take up ammonia, the usual test of litmus may be applied; which
will become red so long as there is bisulphate in solution; and will remain blue
when the bisulphate is decomposed and ammonia is in excess.
The purifyer
for the bisulphates should be lined with lead. In most cases I prefer using
two of the preceding processes in succession, for which purpose I employ two
purifyers, in one of which I commence the purifyation of the gas by either
the first or second of the processes herein-before described, and in the other I
submit the gas to the third process.
I claim under this head of my Invention the purifying of gas by passing it.
through solutions of the bisulphates or supersulphates and sesquisulphates of
potash of soda.
My fourth improvement consists of the following processes for purifying
the gas by means of water, which as the purifycation goes on becomes a solu-
tion of ammonia and its compounds. The water should be as cold as can be
conveniently obtained, for which purpose I prefer that the purifyer should be
fixed in a vessel or tank of greater depth than the purifyer, which is kept
full of cold water for the purpose of keeping the purifying solution at a low
temperature. The purifyer is in the first instance charged merely with water,
and the gas being caused to pass through the water, the ammonia and its
compounds are absorbed by it, but to get the ammoniacal solution in a more
concentrated state or to fix the ammonia, I use one of the following methods:
First, when the water in the purifyer has absorbed or taken up a sufficient
quantity of ammonia and its compounds, it may be drawn off into a saturator,
and the ammonia of the ammoniacal compounds taken up by it be there
combined with a free acid (which I prefer to be sulphuric) or with the acid of
the following salts, namely, sulphate of lime, sulphate of magnesia, sulphate
of iron, sulphate of manganese, muriate of lime, muriate of baryta, muriate of

page_text: iron, muriate of manganese, and acetate of lime, and be afterwards returned
to the purifyer, when it will absorb a further quantity of ammonia, and this
operation may be repeated so long as the ammonia which is combined with
the gas continues to be freely absorbed by the solution. The salts mentioned
above are decomposed by the ammoniacal solution, yielding their acid to the
ammonia, their basis being precipitated as hydrates, carbonates, or sulphurets.
Some of the alkaline earthy salts will require to be well stirred for a consider-
able time with the ammoniacal solution in the saturator to decompose them.
Secondly, this process instead of being intermitting may be conducted con-
tinuously by allowing a stream of the water which is taking up the ammoniacal
compounds to run from the purifyer into a vessel or saturator in which the
ammonia it has absorbed is to be combined with free acid or with the acid of
one of the salts before mentioned, and from which it is returned to the purifyer
again in any convenient way so long as it absorbs freely the ammonia and the
ammoniacal compounds in the gas. To effect this the solution, after the
combination of its ammonia with the free acid or the acid of one of the salts
mentioned, may be pumped from the saturator into a vessel saturated above
the level of the purifier, whence it flows into the purifier in a stream equal to
that which is flowing from the purifyer into the saturator. Thirdly, instead of
allowing the water or ammoniacal solution which is absorbing the ammonia
and its compounds from the gas to be drawn off from the purifyer for satura-
tion or combination, I combine the ammonia absorbed by the solution with an
acid (preferably sulphuric acid) in the purifyer itself by admitting a continuous
stream of acid in sufficient quantity nearly to saturate or decompose the
ammonia and its compounds as fast as they are absorbed by the water or
ammoniacal solution, always taking care. that there is not an excess of acid, and
to prevent any acid ever being in excess it would be best to have some con-
trivance to give notice should such an accident occur.
For this purpose a
piece of zinc suspended in the solution in the interior of a small pipe placed
vertically in the purifyer, and the top of which pipe projects above the top of
the purifyer, and is furnished with a whistle, would answer the purpose, for
in case acid should be admitted into the purifyer in excess it would attack
the zinc and dissolve it, and generate hydrogen gas, which, hawing no escape
at bottom, the pipe being immersed in the liquid), would pass up the pipe and
blow the whistle. Or the generation of hydrogen gas might be made to turn
off the cock supplying the acid in a variety of ways, which will readily suggest
themselves. In this process the acid admitted into the purifyer in combining
with the base of the carbonate and hydrosulphuret of ammonia in the solution
sets free carbonic acid gas and sulphuretted hydrogen, which, when allowed to

page_text: mix with the ordinary gas (carburetted hydrogen) and to pass along with it to
the lime purifyer, has there to be taken up by the lime, causing a considerable
waste of it, and injuring and retarding the process of purification. Therefore,
to prevent these gases, when generated in the purifyer by the combination of
the acid with the ammoniacal compounds in the solution, from mixing with the
ordinary or illuminating gas, I collect them and pass them away. To effect
which I employ an obtusely conical disc a, as shewn in the Drawing at
Figure 1, with a large short pipe b in the centre, which should be introduced
into the purifyer below the ordinary disc for spreading the gas, and the acid
for combining with the ammonia being admitted through a small pipe c in the
top of the conical disc, any gases generated will rise to the under side of the
cone and be conveyed away by another pipe d, also at the top of the cone, as
shewn in the Drawing, to a fireplace or where desired. The apex of the
conical disc being cut off, and the large pipe or opening substituted in its place,
is for the purpose of having a better circulation of the solution in the purifyer.
An angular circular inverted trough, as shewn in Figure 1, may be substi-
tuted for the cone. Instead of having only one spreading disc for distributing
the gas in the purifier, where liquids only are used, I prefer to have two or
more spreading discs, as shewn in the Drawing, and the space between the
spreading discs is to be filled with hard founder's coke or clinkers broken small,
so as to distribute the gas as much as possible and bring it into better contact
with the purifying solution. That no ammonia whatever may pass away with
the
gas, another purification of the same kind or with the bisulphates, as in
the third process, may be added in a second purifier. Fourthly, instead of
saturating or decomposing the ammonical compounds by an acid, they may
be distilled off by evaporation and the water be returned to the purifier again
to absorb more ammonia, &c. The arrangement which I prefer for this
purpose is shewn in Figure 2; the evaporator a is composed of a coil of pipe
which may be heated by the waste beat from the retorts if it can be conve-
niently placed for that purpose, or by a separate fire, as shewn in the Figure.
The purifier 6 is connected at its lower part with the evaporator by a descend-
ing pipe c which communicates with the lowest part of the coil, which, to
maintain a rapid circulation of the fluid should be eight or ten feet lower than
the purifier. To the upper side of the coil is attached the ascending pipe d,
which, to maintain the temperature, may be placed in the flue, which is
enlarged at the upper end so as to form a still head e to deliver off the
ammonia and its compounds, and the sulphuretted hydrogen and carbonic acid
which have been absorbed by the water; this ascending pipe is connected at

page_text: the upper end with the purifier by a zigzag pipe or horizontal worm f (prefer-
ably surrounded by cold water to cool the absorbing water before entering the
purifier again), which enters the purifier a little below the water line so as to
maintain the liquid in the purifier on a level with that in the ascending pipe.
The still head is connected with a receiver by a coil of pipe, also preferably
surrounded with cold water to condense the vapour. When the boiler.. or
evaporator is at work, there is a constant circulation of the water or ammo-
nical solution through the two vessels, the water flowing from the purifier into
the boiler at the bottom, and returning from the boiler to the purifier at top,
and the ammonia and gases which have been absorbed by the water in the
purifier will, as the water arrives in the boiler, be driven off by the heat, and
be passed away through the condenser; and the results, consisting of free
ammonia, carbonate of ammonia, and hydrosulphuret of ammonia, will be col-
lected in the receiver, and the gases may escape or be burnt. The boiler need
only be made to boil sufficiently fast to dispel the greater part of the ammonia
taken up by the water, which should be kept as nearly saturated with ammonia
as may be without letting the ammonia and its compounds fly off in the purifier;
or, instead of returning the water from the evaporator to the purifier, it may
be allowed to run off hot from the top part of the evaporator after it has
delivered off its ammonical products: but in this case an equal stream of
fresh cold water must be run into the purifier to keep the required quantity of
purifying solution therein. In this case the refrigerator between the purifier
and evaporator would not be required.
I claim under this head of my Invention for purifying gas,
First, the combining with a free acid or with the acid of the salts before
mentioned, in a vessel outside or separate from the purifier, the ammonia of
the ammonical products absorbed by the water or ammonical solution while
in the purifier, and returning the solution to the purfier again after the com-
bination of its ammonia with free acid or the acid of the salts before mentioned,
either in a continuous or intermitting process to absorb more ammonia, &c.
Second, for combining an acid with the ammonia absorbed from the gas
by the water or ammonical liquor, which combination is to be effected in the
purifier so as to fix the ammonia as fast as it is absorbed and prevent its being
carried off by the passing gas, thus obtaining a strong solution of salt of
ammonia.
Third, the arrangement for collecting and passing away the gases set free
when the combination of the acid with the ammonia of the ammonical com-
pounds is effected in the purifier, without allowing them to mix with the

page_text: illuminating gas, by introducing the acid below a cone or inverted dish placed
in the lower part of the purifier and having a pipe at its top part for carrying
away the gases.
Fourth, for driving or distilling off by heat, the gases and ammonical
products absorbed by the water, and for returning the water in a continuous
process to the purifiers again, or allowing it to run away after giving up its
ammonical products, &c.
Fifth, for placing two or more spreading dises in the purifier for the better
distributing the gas, and also for the use of coke, clinker, or such like
substances placed between the spreading discs for the purpose of presenting a
greater surface of the purifying liquid to the gas to be purified.
Sixth, for refrigerating or keeping cool the purifying solutions by placing the
purifier in cold water.
My fifth process is to pass steam into the main pipes through which the
gas passes (preferably between the condensers and the lime purifiers), and
which main should be connected to a small refrigerator of any suitable descrip-
tion; this condensor should be ten feet or more from where the steam is
admitted into the main, so that the steam may mix with the gas before
entering the condensor. The steam will unite with a good deal of ammonia of
the gas, and be condensed in the refrigerator from which it can be run off.
I claim under this head the purification of gas by passing steam into
the gas main for the purpose of absorbing the ammoniacal products of the
gas.
My sixth process for purifying gas consists in passing the vapour of muri-
atic acid into the gas in its passage to the lime purifier. To effect this the
muriatic acid vapour may be made to pass in combination with the gas through
a condenser of the following construction:-A light rectangular trough of cast
iron, without a top, is to be lined with slate, flagstone, or brick, set in pitch;
the trough may be about thirty inches square and of any convenient length,
and is divided horizontally into two compartments by a shelf or false bottom
fixed about eighteen inches above the bottom of the trough. This shelf or
false bottom, which should be of slate, stone, or similar material, is pierced
with holes about an inch or two asunder over the whole surface, in which
holes are inserted stoneware pipes about twenty inches long, closed at bottom
and resting upon the bottom of the trough; hot pitch mixed with sand should
be laid upon the shelf to fill up the spaces between the pipes above the shelf,
so as to form, when cold, a gas, steam, and water-tight joint. The pipes. and
the upper compartment of the trough are kept filled with cold water. The
lower compartment of the trough is connected at the ends to the main pipe

page_text: which conducts the gas from the ordinary condensers to the lime purifyers, so
as to form an intermediate portion of such main; and, during the passage of
the gas between the interstices of the pipes, the muriate of ammonia will be
condensed by the extensive cold surfaces with which it comes in contact, and
falling to the bottom it may be drawn off. To furnish the muriatic acid
vapour a small cast-iron cylinder connected with the condenser may be used,
into which common salt and sulphuric acid are put; a regulated fire will
drive off the muriatic acid gas vapour into the condenser, where mixing with
the gas it will combine with the ammonia.
Another mode of supplying the muriatic acid vapour is, first to condense the
muriatic acid from the cylinder in a separate condenser of the above descrip-
tion, and then place an earthen pan full of niuriatic acid at the commencement
of the condenser through which the gas passes, and which pan is to be fur-
nished with an earthen pipe connected to a pipe from a steam boiler. Steam
is then admitted of some little pressure into the earthen pipe, which lays in a
coil at the bottom of the earthen pan, and has a small aperture at its end for
the escape of the condensed water of the steam. The muriatic acid is thus
heated and driven off to combine with the ammonia of the gas with sufficient
steam to ensure its condensation; a constant stream of acid, equal to what
is required for the taking up of the ammonia, may be allowed to run into
the earthen pan by means of a goose-necked pipe which forms a water lute
so as to prevent the escape of any gas. Any other volatile acid may be used
in the same way.
I claim under this head the purifying of gas by mixing with it the vapour
of muriatic or other volatile acids to combine with the ammonia; also the
peculiar construction of condenser for the condensation of the acids, and of
the compounds formed by them with the ammonia.
My seventh improvement consists in certain arrangements for exhausting
the gas from the retorts and forcing it through the purifiers with the view of
causing the gas to pass through a much greater depth of purifying liquids than
is ordinarily employed, without, at the same time, subjecting the retorts to
increased pressure. For this purpose I employ exhausting apparatus working
with a rotatory action. In one of the machines or apparatus which I employ
for this purpose there are two leaves or pistons revolving within a cylinder,
which alternately approach and recede from each other, each in successon
becoming the active piston and the stop or abutment, as in some kinds of
rotatory steam engines.
Figures 3, 4, and 5, represent a machine of this description; Figure 3,
being a front elevation; Figure 4 a lateral section; and Figure 5 a transverse

page_text: section, as seen from the back of the engine. a is a cylinder accurately bored,
and the covers or ends of which, b, b, are made plane and smooth; c is a
narrow slit or opening in the periphery of the cylinder, communicating by a
pipe with the condenser; and d is a similar aperture communicating by a
pipe with the purifier; e and f are two revolving leaves or pistons attached
severally to the spindles and f¹, which turn in bearings in the cylinder
covers, the spindle e' passing through and projecting beyond the spindle f¹.
The thickness of the pistons slightly exceeds the breadth of the apertures so
as to cover them at certain points of their revolution, and they are fitted to
the cylinder as accurately as possible without absolute contact. On the ends
of the spindles are fixed respectively the cranks e* and f*, each standing in
the plane of its piston and connected by the rods e and f³ with the arms e
and fixed upon the driving shaft g. The centre of this shaft is placed
eccentric with respect to the centre of the cylinder, and its position may be
assigned thus:-Upon z as a centre (Figure 6), and with the length of the
crank as radius, describe an arc, and draw the lines y and x in the position
of the cranks when the apertures c and d are covered by the pistons; then
through the centre z draw a line bisecting the arc y, x, and upon y as a centre
and with the length of the connecting rods as radius, describe an arc upwards,
cutting the line in w; and upon x as a centre, with the same radius, describe
an arc downwards, cutting the line in and the central point u in the line
between, the points and w will be the centre of the shaft; h is a rigger
fixed upon the shaft and driven by a band from the driving drum. The action
of the machine is as follows:-Whilst one piston is traversing the circle from x
to y in the direction of the arrows, the other piston traversing from y to a acts
as a stop or abutment.
Another kind of exhausting apparatus which I employ for this purpose is
constructed upon the principles of Capt Ericsson's disc engine, and is shewn
in Figures 7, 8, 9, and 10; Figure 7 being a longitudinal elevation of the
machine (partly in section); Figure 8, a transverse section through the induc-
tion and eduction passages; Figure 9, a back view; and Figure 10, an edge
view of the revolving disc. a is an obtuse cone fixed upon the shaft b, and
revloving within the spherical chamber c; the centre of the cone coincides
with the centre of the chamber c, and the slant side is equal to the radius of
the chamber. This cone is connected at the centre, by a ball and socket
joint, with a disc d, the diameter of which is equal to the diameter of the
chamber c; it is fixed upon an axis e standing at right angles to the slant side
of the cone, and is pressed against the slant side of the cone by the cap f.

page_text: On opposite sides of the cone are fixed two sectoral leaves g', g, which project
through two slits h', h, in the disc, so that the rotation of the cone produces
a rotation of the disc. On each side of the line of contact of the disc with
the cone is a triangular opening (K1, K2,) into the chamber, one forming the
induction and the other the eduction passage for the gas. They extend round
nearly one fourth of the cylinder (as shewn by dotted lines in Figure 7, and
are bounded above by the under side of the disc, and below by the circum-
ference of the cone. m is a pulley fixed upon the shaft b, and set in motion
by a strap from the driving drum. The operation of the machine will be
best understood by reference to the Figure 8; the dotted linen represents
the line of contact between the disc and the cone, and the arrows the direction
in which the cone revolves. The gas enters by the passage K', and being
prevented passing between the disc and cone by their contact at n, it follows
the leaf g¹ until the latter arrives at the passage ³, through which it is forced
into the purifier by the leaf g² during the continuation of the revolution of
the cone.
Where either of these exhausters are employed a governor must
be used to regulate the exhaustion; which governor, if the engine employed is
only used to drive the exhausters, may be attached to the throttle valve of the
engine; but if the engine works other machinery and it is not desirable to
alter its speed, then two conical drums with a strap over them may be used),
the large part of one cone being opposite to the small part of the other, one
cone attached to the engine always going regular, and the other attached to
the exhauster whose speed is regulated by the movement of the strap either
up or down, the cones driving the exhauster quicker or slower. The exhauster
should be of such a size that when the strap is set in the middle of the drum
it exhausts the required quantity of
gas. A governor of the same construction
as a small gasometer, from one to three feet diameter, and rising and falling
in a water tank of the requisite depth for the pressure to be kept in the
main will answer very well. This governor must be connected by a pipe to
the main, so that the pressure in both will be equal. If the pressure in the
main begins to exceed the pressure intended to be kept in it, the gasometer will
rise, and being attached to levers either to the throttle valve or to move the
strap up or down, the conical drums will cause the exhauster to move quicker
until the extra pressure is reduced. If, on the other hand, the pressure
should decrease below the desired point, the gasometer will fall and retard or
stop the exhauster.
I claim under this head the application of the rotatory-exhausting machines
herein-before described, to the purpose of exhausting the gas from the retorts

page_text: and forcing it through a considerable depth of liquid in the purifying vessel
without subjecting the retort to increased pressure.
In witness whereof, I, the said Frank Hills, have hereunto set my hand
and seal, this Seventh day of February, in the year of our Lord
One thousand eight hundred and forty-six.