Im- PROVEMENTS IN AND IMPROVED APPLIANCES AND ARRANGEMENT OF APPARATUS FOR THE MANUufacture and CONCENTRATION OF SULPHURIC ACID
Year: 1874

page_text: LETTERS PATENT to Auguste Ferdinand de Hemptinne, of Molenbeck,
Saint Jean, Brussels, Belgium, Chemist, for the Invention of “Im-
PROVEMENTS IN AND IMPROVED APPLIANCES AND ARRANGEMENT OF APPARATUS
FOR THE MANUufacture and CONCENTRATION OF SULPHURIC ACID."
Sealed the 30th October 1874, and dated the 14th August 1874.
PROVISIONAL SPECIFICATION left by the said Augusto Ferdinand de
Hemptinne at the Office of the Commissioners of Patents, with
his Petition, on the 14th August 1874.
I, AUGUSTE FERdinand de HemptINNE, of Molenbeek, Saint Jean,
Brussels, Belgium, Chemist, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN AND IMPROVED APPLIANCES AND ARRANGEMENT
OF APPARATUS FOR THE MANUFACTURE AND CONCENTRATION OF SULPHURIC ACID,"
to be as follows:-
This Invention consists in improvements in and improved appliances
and arrangement of apparatus for the manufacture and concentration of

page_text: The production of the sulphurous acid takes place in the ordinary
manner in the furnace, serving to burn the sulphur or to roast the
pyrites.
As the formation of the sulphuric acid is accomplished by new
arrangements, herein described, more quickly than by the old plan, the
number of furnaces should be augmented above what suffices for
chambers of equal capacity working after the old method.
Equally with Gay Lussac and Mr. Glover I utilize the heat of the
gas of the furnaces, but in place of using it like my predecessors in
immediate and direct contact with the acid, to denitrify and to con-
centrate which interferes very much with the draught and soils the
product, I make the smoke led by a large tube pass into a leaden
chamber or tubular drum. This drum, supported by an iron frame,
contains some large leaden tubes, closed at the bottom and open at the
top, and soldered into the upper iron floor, covered with lead, of this
chamber. Above this is a second compartment, protected by bricks,
containing a basin in lead, in the bottom of which are soldered small
lead pipes, which descend into the axis of the larger ones, but not to the
bottom. An upper reservoir feeds this second compartment with acid,
and by the difference in the density of the liquid and the heat there is
set up a continuous and rapid circulation, and the surface of the liquid
in this chamber being fed by a jet of steam with the gases from the first
of the series of lead chambers, to be afterwards described, is maintained
favourable to the concentration and denitrification; on the other part,
by circulation the watery vapour and the nitrous gas disengaged from
the acid descends by another pipe into the first lead chamber, econo-
mizing also the quantity of vapour and nitric acid to be furnished to
these lead chambers. The nitric acid for these lead chambers is supplied
to the first one by a glass funnel and flask, fitted with a tap conveniently
placed on the first chamber. The sulphuric acid which has been con-
centrated and denitrified in the tubular drum descends by an overflow
pipe to preparing basins or to a cascade of Gay Lussac after having been
cooled in a worm. This tower, in place of being filled with coke, is
filled with hollow gray balls of pottery, over which the acid is sprinkled
by means of glass turbines, fed by a Perrault's balance.
If it is desirable to sprinkle the cascade with acid more concentrated,
which absorbs the nitrous gas in larger proportion, recourse must be had

page_text: to the concentrating apparatus in pottery, herein-after described, as it is
dangerous to carry this farther than 61° Baumé in the tubular drum.
Lead Chambers.-The sulphurous acid changes rapidly in these
chambers, which are about 10 metres high, 5 metres long and wide;
they are fitted with vessels of stoneware pierced with holes, and so
provide for the circulation of the gas and acid both internally and
externally; they present large surfaces, and are put in activity by
showers of acid from glass turbines, spreading the acid over the surfaces
of the pottery. These turbines are fed intermittently by Perrault
balances, receiving the acid from the before-mentioned reservoir. The
acid from these chambers and from the Gay Lussac tower or cascade is
forced up a pipe into the reservoir by the injector Giffard, fed with steam
from a boiler; it is also fitted with a lateral pipe, by which, if needed,
is drawn in sulphurous acid gas, which is very favorable to the denitri-
fication of the liquid, and thus sent into the reservoir in favorable
conditions. The nitrous gas disengaged in this reservoir is led by a pipe
into the lead chambers.
The concentration to 66° Baumé takes place in a square brick tower,
covered with a leaden dome, forming the bottom of an upper reservoir,
in which is received part of the acid from the former reservoir for cooling
it. An internal circular gutter collects the condensed acid vapour to
prevent it falling into the acid. In the interior of the tower is a hollow
pedestal of cast iron, supporting a vessel of lead, with double sides filled
in with balls of lead, amongst which circulates a current of cold water;
upon this, which is about 15 centimetres from the walls of the tower, is
built up squares of grey pottery, about 15 centimetres cube, pierced with
six holes; one face (the lower) is fitted in this hole with an entering and
projecting tube, intended to retain a thin layer of acid in the interior of
the cube; this also serves to bed the squares when packed in the tower.
The acid is distributed over these squares by a platinum tube and
Perrault balance, and is concentrated by steam superheated to 450° to
500° centigrade, supplied to the tower by a pipe from an iron retort
filled with balls of iron attached to a furnace and boiler.
The par-
ticles of iron are retained by a filter of asbestos. The concentrated
product is received without any contact with the walls upon the double
bottomed lead vessel, and passes by a pipe to the cooling cistern ready
for delivery.
. The excess of steam is carried to heat a concentrating vessel, and the

page_text: condensed vapour applied to iron shavings or clippings of tinned iron,
by which sulphate of iron or both sulphate of iron and tin is procured.
Any remaining excess is then carried away by a flue or sent into the
chimney shaft of the works.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Auguste Ferdinand de Hemptinne in the Great
Seal Patent Office on the 2nd February 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Auguste
FERDINAND DE HEMPTINNE, of Molenbeek, Saint Jean, Brussels,
Belgium, Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourteenth day of August, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Augusto Ferdinand de Hemptinne,
Her special license that I, the said Auguste Ferdinand de Hemptinne,
my executors, administrators, and assigns, or such others as I, the
said Auguste Ferdinand de Hemptinne, my executors, administrators,
and 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 AND IMPROVED
APPLIANCES AND ARRANGEMENT of Apparatus for THE MANUFACTURE AND CON-
CENTRATION OF SULPHURIC ACID," upon the condition (amongst others) that
I, the said Auguste Ferdinand de Hemptinne, my executors or admi-
nistrators, by an instrument in writing under my, or their, or one of
their hands and seals, 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 Auguste Ferdinand de Hemptinne,
do hereby declare the nature of the said Invention and in what manner.

page_text: the same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, that is to say :-
:-
In conjunction with the accompanying Drawings forming part of this
Specification, and in which Figure 1 is a sectional elevation of the
apparatus developed, and Figure 2 a portion of the apparatus on a larger
scale, the like letters referring to the like parts in both Drawings.
The production of the sulphurous acid takes place in the furnace A
serving to roast the pyrites.
As the formation of the sulphuric acid is very active, from the
arrangements that I will describe afterwards, the number of these
furnaces should be augmented beyond the numbers working with the
chambers of equal capacity working after the old methods.
To economise space and masonry and to regulate the draught I adopt
a circular form, that is to say, the twelve furnaces are grouped, disposed
in a circle, leaving in the middle a free space B covered with cast-iron
plates which serves as a large condensing chamber for the pyrites' dust
which is taken out by the openings B¹, B¹, and the ash doors. The fine
pyrites may also be roasted on platforms of refractory material fitted up'
under the large leaden tubes of the drum D which I will describe
presently, but in this case the drum ought to be in cast iron. From
this drum a large square chimney of lead C³ conducts the gas into the
first leaden chamber F. Similarly with Gay Lussac and Glover I
utilize the heat of the gas from the furnaces or hearths, but in place of
putting the hot gases in direct contact with the acid to be denitrified,
and to be concentrated like my predecessors, which prevents very much
the draught and causes loss of time and spoils the product, I pass the
fumes into the cylindrical drum of lead D. The drum of three metres
diameter is supported exteriorly by an iron frame formed of two
platforms and a circular band supported by twelve little columns con-
solidated by cross round picces behind which the outer air can circulate
and cool the lead, the manufacturers of acid have noticed that the leaden
chambers are more powerfully attacked at the places where the metal is.
covered up
and kept hot by the framework of the scaffolding..
I suspend across the platform of the drum, in iron covered with lead,
ninety-four large pipes of lead of ten centimetres in diameter which are
closed at the bottom and open at the top, and opening into the compart-

page_text: ment which is established above the large pipes of four metres of length
instead of resting on a platform are solidly hung to the platform, and
being thus free can expand or even twist a little. The upper compart-
ment contains at some distance from the sides a sheet of thick lead E
supported by inattackable bricks, into which are soldered ninety-four
smaller pipes of lead, descending and leading down the axis, and 30
centimetres from the bottom of the large pipes the sulphuric acid which
flows constantly by the pipe Nº. By the effect of the heat of the gas
which envelopes and plays upon the great tubes, and from the difference
in density of the liquid, there is established in these two series of pipes
and upon the sheet of lead E a continuous and rapid circulation favorable
to the concentration and denitrification of the acid; that denitrification is
set in action by the sulphurous acid gas drawn in (free from dust) from
about the middle of the first chamber F by the force of a jet of steam
established in the axis of the pipe G. The gas licks the surface of the
acid, always being renewed; on the other part, the watery vapour, tho
sulphurous acid gas in excess, and the nitrous gas disengaged from the
acid are conducted into the chambers by the pipe H; the vapour and
the nitric acid which must be supplied to these apparatus is thus
economised.
I remark here that the nitric acid necessary to the manufacture is
supplied by a little glass cask T with a cock and funnel which is placed
in the frame of the platform of the chamber above a glass tube S fitted
with a funnel. The sulphuric acid which has been concentrated and
denitrified in the drum D delivers itself by the overflow pipe L either
to the preparing cisterns I and J, or when it is up to 60° to the cascado
of Gay Lussac K, after having been for this last purpose previously
cooled in the lead worm M.
I need not refer in my Patent to the cascade of Gay Lussac, only I
may remark that if it is desired to sprinkle the interior of this cascade
with concentrated acid, which absorbs as is well known the nitrous gas
in a much larger proportion, recourse must be had to the concentrating
apparatus in pottery which I will describe presently; it would be
impossible to push the concentration above 62° Baumé in the leaden
pipes of the drum D because they would be eaten away by the acid.
Leaden Chambers.-The sulphurous acid changes rapidly and econo-
mically into sulphuric acid in the three leaden chambers F, F, F, which are

page_text: cach ten metres in height and five metres in length and breadth. They
are filled with round vases in stoneware pottery of about 50 centimetres
diameter, pierced with round holes of 2 centimetres, and giving large
surfaces for condensation, put in action by a shower of hot acid that the
glass turbines R distribute to the surface of the pottery. These tur-
bines R are put in motion intermittently by the three Perrault
balances S¹ receiving the acid from the reservoir N by the pipe with.
stoneware tap N³. If it is desired to give a greater height to the.
chambers (which would be an advantage for sprinkling a larger number
of the vases) the corresponding parts of the apparatus must be equally
raised.
Elevation of the Acid.-The acid flowing from the chambers of the
Gay Lussac column, led by the pipe 0%, is thrown into the reservoir N
by the injector Giffard O, which must be carefully fixed below the level
of the acid to be raised. I have given to this apparatus the proportions
indicated by the Inventor for the pumping of water only. I have
constructed it in an alloy of lead with a steam jet of platinum. I have
fitted it also with a lateral jet O³ with a tap intended to draw in and
to force with the acid sulphurous acid gas, which is very favorable to
the denitrification which already commences in the elevating pipe O¹.
The mixture is then furnished in excellont conditions to the leaden
reservoir N, which is closed by a cover and protected in the interior by
refractory bricks or tiles of porphyry or glass. In this reservoir is set
free the nitrous gas which is led to the chambers by the leaden pipe Q..
A small glass float N₁ enclosed under a glass bell indicates the level of
the liquid in the reservoir.
Concentration of the Sulphuric Acid to 66° Baumé.-The concen-
tration to 66° is made in the round tower of hard bricks U having a
high door, which is built up before the apparatus is set to work. The
tower has for its roof a cylindrical basin in thick lead V with a hollow
bottom, in the which a part of the acid from the reservoir N is placed
for the cooling of it, which then flows into the basin I. A circular gutter
gathers at the base of the dome the condensed acid vapours and conducts
them outside by an overflow pipe in lead V₁; they cannot thus fall into
the acid which is concentrated in the tower. This concentration is
effected in the following manner:-In the interior of the tower, at 15
centimetres distance from the wall, upon a hollow well-bevelled pedestal
in cast iron, I build up a pile of hollow vessels in stoneware pottery, 15

page_text: metres on each side, and pierced with six round holes of 6 centimetres
each; these vessels moulded and baked with care should be perfect
cubes, which is necessary to the stability of the edifice, and which is
constructed without any mortar. One of the holes of these vessels, that
of the lower face, is furnished with a short pipe which enters into the
interior and projects outwards, intended to retain a small layer of liquid
on the bottom of each vessel; the retension of the acid thrown on the
top of the tower in the vessels is thus prolonged. These short pipes
serve also to steady and to bind together the vessels, which being well
placed cannot slip one upon the other.
For excess of safety the upper layer of vessels may be lapped round
with the platinum wire, forming a frame which can be attached to the
walls of the tower. The sulphuric acid arriving from the preparing
basins or flowing from the preparing basins I, J, into the Perrault
balance W is distributed either by a turbine in platinum or by a
rose, and trickles over the surface, and in the interior of the
vessels it becomes concentrated to 66° by the action of steam super-
heated to 450 or 500° in the large cast-iron retort X, which is filled
with balls of iron, or better, of copper, which conducts the heat better.
To retain the metallic particles, which could be drawn out from the
retort and soil the acid, I pass the superheated steam into the filter
box U¹ filled with asbestos, which is let into the thickness of the wall of
the tower, which is well bound together. I have represented on the
Drawings the cast-iron retort X heated in the boiler furnace P.
In view of preventing any delay it may be installed in a special
furnace, or it may be heated below in the leaden preparing basins;
whatever the disposition adopted the sulphuric acid concentrated
and protected from the dust of the wall (because there is a space at the
bottom of the tower to gather the dust) is received at the bottom of the
pile of the vessels into a leaden basin with double sides. The interval
between these sides is filled with iron balls, which support the weight of
the vessels, and a continuous current of cold water circulating between
the balls prevents the attack of the acid upon the lead of the basin.
Another current of water cools the lead pipe, which is enveloped with
a case of copper; this pipe conducts the product into the leaden
cistern Y, surrounded with water, from whence the acid is poured out
into the bottles to be sent away.
As to the excess of vapour in the tower it is conveyed and utilised:

page_text: almost entirely in the flues of the large concentrating basins, which it
warms, whilst the sulphuric acid vapours are conducted over shavings or
nodules of iron supported on a grating and watered from time to time;
the sulphate of iron formed is received into the lower part of the
casting Z, which occupies the bottom of the flue. The remainder of the
vapour and gas is led by an underground passage into the high chimney
of the factory.
It is prudent for the prevention of explosion of the hydrogen gas
produced by the gas to furnish the extremity of the underground passage.
with wire gauze or plates of iron pierced with small holes.
So as not to interrupt the description of the apparatus above I have
omitted several points of the chemical theory and some details of con-
struction, to which I will now refer.
Drum D for Denitrification and Concentration.-If a crack shows.
itself in the large pipes of lead suspended in this chamber it would
be better to stop it up or to flatten it than to seek to replace it; a little.
leaden door serves for the cleaning of the exterior of these tubes. As to
the cleaning of them inside, which can be done by taking out the ends of
the pipes, it should be rarely done because the active circulation of the
liquid brings up into the upper compartment the sulphate of lead
which would be disposed to rest at the bottom of the large pipes; the
lead worm M which cools the acid intended for the cascade of Gay
Lussac is fitted upon the level of the soil, so that it is not necessary to.
lift very high the water required for cooling it.
Leaden Chambers.-The three chambers indicated in the Drawings
constitute a battery. In the large factories the batteries must be
multiplied, because it would be impossible to install a larger number of
chambers, the one following the other, on account of the difficulty of the
draught; the chambers occupying little space, 50 centimetres of surface,
and economizing the land, are covered with a roof in tiles or asphalted
felt or paper. The scaffolding should be more solid than that employed
for the ordinary leaden chambers, it is firmly fixed by strong rods of
iron bolted and fitted in cross pieces of wood, and with planks to resist
the thrust of the spherical potteries in the interior. As the lead will
be more quickly destroyed than the pottery it is useful for avoiding the
replacing these numbers of stoneware vessels to give 5 millimetres of
thickness to the sheets of the sides, and to double the soldering fitting
of the angles; the lead of the floor ought to be thick also so that it shall

page_text: not give under the weight of the pottery; strong buckled plates of lead
F, o, pierced with holes are soldered before the opening of the first pipe of
communication of the chambers, and before the outlet pipe to restrain
the pottery, which would otherwise obstruct these passages.
It is hardly necessary to advise the choice of pottery perfectly resisting
the action of acids. The 5,200 vases pierced with holes produce the
same useful effect (without complication of pipes of communication) as
if the gas was passed into a series of 10,400 recipients of the same size
placed one following the other, because the interior and exterior surfaces
of the condensers are utilized when they are in a chamber of lead.
The 5,200 vessels present 7,800 square metres of condensing surface,
and the three leaden chambers 750 meters; together, 8,550 square metres.
If the square metre of lead of 5 millimetres thick, weighing 56 kilos.,
the metre costs 36 fcs. 40, the square metre of pottery does not cost
more than 3 fcs. 50, or 4 fc. The surfaces in pottery not being acted upon,
the product obtained contains much less sulphate of lead than that from
the ordinary chamber. The formation of the sulphuric acid being a
question of surface and not of volume it is produced here under the best
possible conditions, because the condensing surfaces wetted by the hot
acid are considerable. It has been remarked that in fact that the
greatest action of the gas in the chambers takes place in the lower
layers, that is to say, where the acid on the bottom is licked by the air
and the sulphurous and nitrous gases.
By my process the nitrous compounds lost in a great measure in the
different layers of sulphuric acid of the chambers are continually
brought into contact with the sulphurous acid. Moreover the continual
circulation of the liquid disperses the flowers of sulphur which some-
times remain in a light crust on the surface of the acid more or less
stagnant in the ordinary chambers. The liquid which trickles over the
vessels at the degree of temperature and concentration suitable causes
the solution of the crystals, and rapidly transforms the sulphurous acid
into sulphuric acid in the numberless sinuosities that the gas has to
pass through.
When it is necessary (but very rarely) to inject steam into the
apparatus it may be done by the pipes of copper and lead P¹, but for the
draught there must be worked continuously the steam jet of the pipe G
as well as the large jet which is in the axis of the lead pipe K', which

page_text: conducts the gas of the apparatus of Gay Lussac K into the chimney of
the boiler P.
Turbines or Barkers Mills.-I have for a long time employed in my
factory the turbine for sprinkling the cascade of Gay Lussac. These
turbines are very useful in my new system, because it would be very
difficult without them to spinkle uniformly the surface which each has.
of 25 metres. They may be made either with one or two branches, but
I prefer the one with one branch in the form of an L, because they are.
more easily introduced into the chamber or taken out of it by a narrow
opening by inclining diagonally the long branch.
The horizontal branch of 55 centimetres of length is pierced with
small holes on one side. The vertical tube of glass is three metres long.
This height is necessary for the dispersion of the acid over a large
surface of pottery. The tube terminates in a funnel sufficiently large to
fill the apparatus simultaneously. When the glass funnel runs over the
excess of acid is received in a funnel envelope, which conducts it along
the tube into the round opening by which passes the turbine. The two
tubes of glass of the turbine unite and are cemented together by sulphur
into a little collar of platina or lead, under which is fixed a glass point
or an agate, which turns in a little mortar of the same material forming
the step. The agate mortar is fixed solidly upon a cross piece in wood
enveloped in lead or on a lead pipe, supported inside by a bar of iron,.
which is suspended in the roof of the chamber. I prefer to have the
greater part of the turbines outside the chamber so as the better to.
dispense the acid and not to diminish the space reserved for the earthen
vessels contained in the interior.
The turbine is guided in its movement of rotation by a disc in thick
lead, cut in half and dovetailed, which rests on a wood cross piece a little
below the glass vessel,
The vertical tube is fitted in the part of the cross piece of the ceiling
of the chamber in a little glass bell, which allows it to turn with very
little friction in a little gutter of acid, which makes an hydraulic closure
and prevents escape of gas.
As it might happen that the holes of the turbines should become
closed, it is a good plan to mount four of them near the middle of each
chamber, at 60 centimetres from each other, upon a support in form of a

page_text: cross, where they turn like the turbines in a firework device. By these
means the sprinkling of the vessels may be varied or augmented.
Perrault Balance.-I have said that I put the turbines in action inter-
mittently by means of this balance, which may be constructed thus:-
The acid led by the stoneware tap N³ is received into the double trough
in lead of sufficient size, which should furnish successively to four
distributing pipes a quantity of liquid sufficient to put the turbines in
rapid movement. The acid before passing into the vessel is filtered
through the strainer in the cover of the instrument, and the passage of
the particles which might otherwise stop the holes in the turbines is
prevented. The bottom of the lead box forms an obtuse angle, so as to
form a support to the balance, when this tips up without derangement
on the two outlets at the bottom of the box. For this purpose the
bottom of the box is lined with wood. The balance is retained in the
upper groove of the support by a knife edge, made of an alloy of lead
and antimony, soldered on the bottom of the trough.
New Application of the Injector Giffard.-I have found the employ--
ment of this injector, or some modification of it, of great service,
because it takes the acid to the cascade of Gay Lussac at the degree
favorable to the denitrification, and that it gives to the acid of the
chambers the temperature and the degree proper for the chemical
reactions. The vapour of water dispersed by the injector replaces that
which is necessary in the ordinary process for the fabrication of sulphuric
acid. The novel idea of my Invention in this respect consists also in
drawing in with the sulphuric acid sulphurous acid gas, which serves
for the denitrification.
I have already said that the injector is made of a box in an alloy of
lead, in which the vapour was injected by a little pipe in platina,
drawing in on one side the sulphuric acid by the pipe O³, and on the
other side sulphurous acid gas by the pipe O³, which is fitted with a
regulating cock made with glass rings. The acid should arrive at the
injector (fixed below the level of the soil) without aspiration from a
higher level by a natural fall from a pipe always full, so that there shall
be no stoppage of the action when it is put to work, and also that the
liquid may traverse and cool the apparatus if the steam should be thrown
back into the pipe. The steam arrives from the boiler P by a thick lead
pipe, which first rises to a height of 7 metres above the level of the

page_text: earth, then descends to the pipe Giffard. I adopt this plan to transform
the pipe into a barometrical tube inapproachable by the acid, which other-
wise might be aspired from the vacuum produced by condensation of
the vapours after closing of the taps. One can thus do without a check
valve. In relieving the pipe of steam the brass cock is also protected
from contact with the acid.
Having now described and particularly set forth the nature of the
said Invention, and the manner of carrying the same into effect, I would
have it understood that what I claim is,-
First. The tubular heating apparatus placed in the flues of the furnaces,
substantially as described.
Secondly. The denitrification out of contact with the dust of the
furnaces or pyrites of the acid of the lead chambers, and the acid of the
Gay Lussac towers, substantially as described.
Thirdly. The application of the vessels in pottery to the leaden
chambers to increase the acting surfaces and the continuous sprinkling
of the said vessels with hot acid drawn from the bottom of the chambers,
substantially as described.
Fourthly. The employment of the injector Giffard for the lifting and
heating of the acid, and for its denitrification by means of steam and
sulphurous acid gas aspired with sulphuric acid, substantially as
described.
Fifthly. The concentration by superheated steam of the sulphuric
acid trickling over vessels in pottery supported away from the enclosing
walls of the tower, substantially as described.
In witness whereof, I, the said Auguste Ferdinand de Hemptinne,
have hereunto set my hand and seal, this Twenty-seventh day of
January, in the year of our Lord One thousand eight hundred
and seventy.
A
TL TLMDTINNT