Im- PROVEMENTS IN THE CONSTRUCTION ОР APPARATUS FOR CONCENTRATING SULPHURIC ACID
Year: 1870

page_text: LETTERS PATENT to Auguste Ferdinand de Hemptinne, of Brussels,
in the Province of Brabant, Chemist, for the Invention of "Im-
PROVEMENTS IN THE CONSTRUCTION ОР APPARATUS FOR CONCENTRATING
SULPHURIC ACID."
Sealed the 9th May 1871, and dated the 12th November 1870.
PROVISIONAL SPECIFICATION left by the said Auguste Ferdinand
de Hemptinne at the Office of the Commissioners of Patents, with
his Petition, on the 12th November 1870.
I, AUGUSTE FERDINAND DE HEMPTINNE, of Brussels, in the Province.
of Brabant; Chemist, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE CONSTRUCTION OF APPARATUS FOR CONCENTRATING
SULPHURIC ACID" (to be as follows) :-
The object of this Invention is to substitute lead for platinum or gold
which are now used for the construction of the boilers, stills, or alembics
employed in concentrating sulphuric acid.
The leaden apparatus consists of a rectangular boiler, still, or alembic
of any suitable size, made of sheet lead of about one-third of an inch

page_text: gauge, and closed all over, & this boiler is entirely filled with square
blocks or cubical boxes of sandstone or stoneware fitting close against
each other and the sides or internal casing of the boiler so as to prevent
The
the lead from bulging in or collapsing when there is a vacuum.
said cubes are made hollow, their bodies or sides being thin but strong,
and in each side there is a hole coinciding with or facing the corre-
sponding hole of the contiguous cube. Thus the diluted acid when let
in will freely fill the cavities of the blocks or tubes, and then by con-
nection will gradually be subjected to the caloric action of a suitable
fire placed underneath the boiler, and the gases of the said fire after
having crept over the bottom of the boiler will finally escape into the
chimney through a set of lead pipes extending across the lower rows of
The boiler or still is fitted
cubes through the holes before mentioned.
at the top with a collecting tube for collecting the vapours evolved from
the acid in process of concentration, and passing them through a leaden
worm placed in a water trough to be condensed, and afterwards collected
in a suitable recipient; and the said leaden alembic is also provided out-
side with an arrangement of cooling tubes devised for the purpose of
preserving the leaden metal at the time the concentrated acid is drawn
off and air is let in. This arrangement consists of iron pipes perforated
with minute holes placed round the boiler and in communication with
a water tank, the stop-cock from which need only be turned on to
produce the cooling shower required.
The improved apparatus is operated in the following manner: —A
vacuum is produced in the still either by Bunsen's (of Heidelberg)
hydro-pneumatic pump, or by any other suitable means; acid of 60
degrees is introduced by a proper syphon; then heat is applied by
means of the fire-place under the boiler, and as soon as the thermometer
dipping into the central portion of the still reads 205 degrees Centigrade
The fire is then withdrawn, and the outside
the operation is complete.
of the boiler watered over in order to cool it; the usual syphon is
employed for decanting or extracting the concentrated acid, and air is
allowed to enter the boiler or alembic. This concentrated acid is stored
away in proper vessels, and the apparatus is at once ready for a fresh
operation.

page_text: 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 11th May 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, AUGUSTE'
FERDINAND DE HEMPTINNE, of Brussels, in the Province of Brabant,
Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of November, in the year
of our Lord One thousand eight hundred and seventy, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Auguste Ferdinand de Hemptinne,
Her special licence 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 THE CONSTRUCTION OF APPARATUS
FOR CONCENTRATING SULPHURIC ACID," upon the condition (amongst others)
that I, the said Auguste Ferdinand de Hemptinne, my executors or
administrators, 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 my said Invention, and in what manner
the same is to be performed, to be particularly described and ascer-
tained in and by the following statement (that is to say) :-
The object of this Invention is to substitute lead for platinum or gold
which are now used for the construction of the boilers, stills, or alembics
employed in concentrating sulphuric acid.
The sulphuric acid is concentrated to the strength of 66° Baume in a
leaden alembic or boiler closed all over which the walls are about one-
third of an inch in thickness, and the alembic or boiler is marked A

page_text: in Fig. 1 of the accompanying Sheet of Drawings. In order to enable
the alembic to resist the pressure of the atmosphere it is tightly filled or
packed with cubical boxes or frames made of porcelain, stone, or
earthenware, which will not be attacked by the acid, the boxes having
their sides of about six inches square surface or other suitable dimensions.
These boxes, regularly moulded and baked, have in each of their sides
'round holes to allow the circulation of the liquid and gas in the interior,
and also make a passage for the leaden pipes G, G, G, composing the
There are two kinds
tubular heating apparatus herein-after described.
of boxes in the interior; first, a series having five holes, each between
three and four inches in diameter, and one of two inches diameter; and
the side with the smaller hole is placed in contact with the walls of
the alembic in order to prevent the lead from bulging or collapsing by.
the pressure of the atmosphere. The sides with the smaller holes, as
well as those having the larger holes, to allow the passage of the tubes
are bristled with projections or pyramids to allow the circulation of the
acid and gas around the boxes, for if there were no projections the
imprisoned acid would become overheated, and the metal would be
corroded and melted. A second series of earthenware or stoneware
boxes, having their sides pierced with holes, but without projections, are
employed for filling up the interior of the alembic or boiler.
arrangement I make a vacuum by employing a fourfold steam horn,
represented in Fig. 3, which is bolted to the large cast-iron receptacle H³,
Fig. 1, which is perfectly closed. When the injection of steam is
stopped after shutting the valve H³, which is mounted with india-rubber
and the air cock B³, a vacuum is produced by external cooling or by
the injection of water, the vacuum being divided with that which is
being obtained in the alembic, thus economising. steam and water
expended the horn.
In one

page_text: the hot water running off through the pipes T and R; but in the
Drawing this reservoir is shewn too small. When a column of falling
water cannot be obtained a good vacuum may be procured by means of
the hydro-pneumatic pump M², Fig. 1, invented by Mr. Bunsen, Chemist,
of Heidelburg. This apparatus is placed on a flooring at about forty-
three feet from the ground, but if a well of about forty feet deep is made
to receive the pipe M² for the fall and evacuation of the water the
apparatus can be placed at the level of the ground, but in either case the
pipe M should have an internal diameter of between four and five
eighths of an inch. The pipe for the exhaustion of the air, which has a
bore somewhat larger than half an inch, has at one end a 3ths hole,
and this pipe should incline towards the condensing worm in order that
the extraction of the air should not be hindered or prevented by the
water in the pipes. The reservoir or tank containing the supply of
water is furnished with a cock for regulating the delivery of the water,
and also a self-acting cock, which is not represented in the Drawings,
for closing the supply passage if the tank should fail to be supplied with
water; and in the Drawing the horn is supplied from the large
reservoir D, the water escaping from the bottom into a drain or well.
A horn resembling Giffard's "injector" may also be employed by taking
care that a refrigerant should be passed through beforehand, because
the hot water on account of its temperature diminishes the amount or
degree of vacuum obtained by Bunsen's apparatus, for the same reason
the heated water of condensation from the alembic cannot be advan-
tageously utilized.
.
I have found it useful to place the air cocks B² and B³ near the tank
for the supply of water to the worm under water in a small vessel having
compartments which hinder the re-entrance of air, and indicates any
defect in either of the cocks. When the vacuum is made the sulphuric
acid previously concentrated in free air without a vacuum to 60° or 62°,
and brought to the vessel F and gauged, is afterwards received in the small
leaden cistern P, from which the syphon N draws it into the alembic, and
it is this syphon that serves at the end of the operation to draw off the
acid concentrated to 66°. The fire is made in the furnace I as soon as the
alembic is filled, and I may remark that it is useless to make the vacuum
until the acid boils. The acid vapours arising from the ebulition are con-
ducted by a series of curved pipes J, J, J, to a pipe K enclosed in a
refrigerating case or jacket, and then the condensation is finished in the

page_text: large worm K' having a sufficient number of coils. Instead of employing
a jacket, I have found it more easy to plunge the pipe K, which is about
twenty feet long, in a gutter having water overflowing. The liquids
called small waters are received in the receiver L, formed of two round
stoneware vessels pierced with holes and laid end to end, the vessels
being encased in a jacket of lead about one-eighth of an inch in thickness.
These stoneware vessels sustain the lead so that it perfectly resists the
pressure of the atmosphere, but when desired instead of a cylindrical
receiver I employ a cubical leaden case filled with earthen or stoneware
boxes, similar to those contained in the alembic; I give to this receiver
a capacity somewhat larger than shown in the Drawing, in order that
it may receive the acid which is sometimes carried by spurts outside the
alembic, for in fact there is tumultuous ebulition when after allowing
the vacuum in the alembic to be lessened it is quickly increased to the
degree at which the boiling commences. I here remark that it is
advantageous to maintain the vacuum to the highest possible degree, for
when the boiling acid has a lower temperature, and thereby the corrosion
of the lead is prevented, and also the production of gas which lowers the
level of the mercury on the tube of the barometer. When the acid is
concentrated to 66°, that is to say, when the vacuum being maintained
at twenty-eight inches and three-eighths, the large mercurial barometer Q
indicates 190 to 195 degrees centigrades, the fire is withdrawn from the
furnace I, and the two water cocks 1 and 2 are open to communicate
with the perforated iron pipe which surrounds the upper part of the
alembic, and then the water from the reservoir D at both sides gushes
with pressure on the walls of the leaden boiler or alembic, and cools the
acid and preserves the metal from the action of the heat during the
withdrawal and refilling. The hot water descends into the sheet iron
cistern S, which contains the leaden alembic and runs off by means
of the pipe T, and the cistern rests upon a vault of fire-bricks. When
the acid at 66° is sufficiently cooled it is drawn out by the leaden
syphon N which remains primed, or it can be easily made so by the
vacuum yet existing in the alembic; in fact when the cork V herein-
after described is opened, the acid is drawn out by the syphon N to the
cistern P. The syphon N being primed, the running off is regulated
by allowing the entrance of air to the boiler by the cock B2 or B³, and
the acid is received into decanting cisterns T2, of from one thousand
one hundred to one thousand three hundred and fifty gallons capacity
for the purpose of allowing it to deposit when sheltered from the

page_text: contact of the atmosphere the small quantity of sulphate of lead
contained in the liquid. The clarified or purified acid is drawn out
through a stoneware cock, or by preference through a short branched
syphon in order to avoid the white deposits which take place when the
pipes are long. Instead of the large leaden cisterns, in which if an
operation fails much acid is spoiled, I may employ large stoneware
vessels or vases having corks at different levels. The cork at the top
would allow the decantation of the clarified or purified acid, and by the
lower cork the sulphate of lead deposited at the bottom of the vessel
could from time to time be taken off. This deposit is not lost whilst in
an apparatus of platinum it dissolves a notable quantity of this precious
metal, in which is passed freely in the acid of commerce. Before
commencing a fresh operation care must be taken to draw out through
the wall the small waters contained in the cylindrical receiver L, and
it is to be understood that the fire is not to be re:lighted until the
alembic is again filled.
I now describe some of the parts more in detail, and first remark
that one can apply without much cost to the alembic the several
appliances actually used for the concentration in platinum vessels.
The furnace I is best to be isolated to facilitate the cleaning of the flues
and the reparation of the boiler or alembic. The heated air which
passes under the cistern S and through the pipes G does not enter by
a single flue, which produces spurts of heat, but passes first into a flue
having at each sides small flues or holes to divide the heated air or
smoke into small channels before it arrives at the flue in contact with
the boiler. The hot air afterwards traverses the leaden tubes G, G, G,
placed lengthways in the apparatus, and passes to the chimney after
heating the walls of the lead in contact with it, and these tubes of lead
are provided with holes covered with caps, so that the tubes can be
cleaned weekly, or as often as required. The mouths of the tubes are
covered with sheet-iron sockets or cases to protect the soldered joints
from the action of the flame..
Although the alembic or A, intended as a substitute for the costly
platinum apparatus at present in use, may be constructed on a large
scale without great expense, with perfect hermetic closing, and be
capable of being cleaned with facility, it is better in large manufacturies
to have several alembics or boiler of a medium size, for example, about
245 gallons capacity, because an apparatus much larger demands a great

page_text: surface of lead, and also the leaden pipes K and worm K would have to
be so large that they might give way to the atmospheric pressure; and
also the construction of a very large alembic is difficult because it is
necessary to reverse it to be able to solder the tubes.
A single operative will be sufficient to attend to the several parts of
the apparatus if the engineer employed to construct them has taken
care to collect in the same factory receptacles, reservoirs, worms, horns,
pipes, and cocks represented in the Drawings.
I have said that I sustain the walls of the alembic by hollow boxes
well packed together, the projecting pyramids on the boxes preventing
the lead from becoming so soft by the heat that it might melt on the
boxes. The acid can also circulate through the spaces between the
projections, and thereby prevent the overheating of the metal, which, if
it occurred, would not be indicated by the thermometer contained in a
leaden tube in the middle of the boiler. In the case of overheating the 1
metal would be attacked first with sulphurous acid, then with flower of
sulphur, and finally with hydro-sulphuric acid.
The boxes give passage to the pipes composing the tubular warming
apparatus, which I claim as my Invention and property, for the con-
centration of sulphuric acid up to 60° in leaden vessels heated in free
air, and also when a vacuum is used. In the generally adopted at
present to obtain the concentration it is only the bottom of the cisterns
that are submitted to the action of the heat, whilst with the tubes and
boxes which sustain the walls and interiors of the boilers. These tubes
arranged lengthways in order to diminish the number of solderings in
the walls.
In watering the alembic at the end of the operation I have sur-
mounted a serious difficulty, which has perhaps overcome my predecessors,
for during the employing and refilling the alembic the lead is exposed
to the effect of the heat accumulated in the masonary of the furnace, a
which might raise the acid to the thermometric heat at which the metal
would begin to corrode. This accident is avoided and the concentrated
acid can be quickly withdrawn by watering the walls and the bottom of
the alembic with cold water by means of the perforated pipe before
mentioned.
I may here speak of the continuous concentration in which the
watering is dispensed with, thereby avoiding those abrupt transitions
of heat and cold which are prejudicial to the lead and masonry of the

page_text: alembic. In this case it is necessary to have much longer alembic, and
cause the acid at 60° to enter in a small channel at one end to be
withdrawn at the other end at 66°, and then to pass it, after cooling,
into two recipients, from whence it can be alternately withdrawn by
cocks without destroying the vacuum required in the interior. It is
necessary also to collect the small waters in two vases hermetically
sealed and capable of resisting the pressure of the atmosphere. Again;
if it is not wished to adopt for intermittent concentration the tubular
heater on account of the difficulty in the contraction and reparation of
the alembic, the same heating surface can be obtained in a vessel much
longer and higher, from whence it would be easy to withdraw the stone-
ware boxes in case of accident; with the leaden tubes this withdrawal
of the boxes is more difficult, and some of the lower ones may be
broken when the alembic has to be repaired. The apparatus H to make
the vacuum consists of a cylindrical steam box made of brass, in the
centre of which there are five conical pipes of different dimensions
boxed one into the other, so as to leave between them at their ends thin
annular spaces. It is by these passages that the steam escapes from
the box with a speed sufficient to balance the pressure of the atmospherė
by means of the thin films of steam, and thus there is a suction in the
vessels with which this apparatus communicates.
I now describe the two leaden cocks V and W, each plated with annealed
glass, and which good results. At the bottom of the space in the shell
of the cock is connected a disc of cut glass having a three-quarter inch
lateral hole, and to prevent the disc from turning and closing the passage
in the cock there is a small hollow cut at the edge of the disc and filled
with lead. The plug Z is also furnished with a glass disc having a lateral
hole, and fixed by means of a hollow filled with lead. When it is
required to make the two openings correspond, that is, to open the cock,
the key is turned by means of the small iron handle V and W, and then
the liquid traverses the canal boxed in the two pieces and flows through
a bent pipe into the overflow cistern P, used for immersing the cock
and preventing the entrance of air. The holes in the taps are made
large enough to be able to accelerate the emptying and refilling the boiler,
and thus the vase when it is nearly empty is only a short time exposed.
Having now described the nature and particulars of my said Inven-
tion, and the manner in which the same is to be performed, I desire it
to be understood that I claim,—

page_text: First. The system of sustaining by internal boxes or framework of
porcelain, stone, or earthenware, unattackable by acids, the walls of
the leaden alembics or boilers in which there is a vacuum, and intended
to replace the platinum alembics at present used to concentrate sulphuric
acid to 66°.
Secondly. The application of the tubular heating apparatus to these
leaden alembics and also to the cisterns in which the acid is concentrated
in the open air to 60° or 62°, thereby effecting a sensible economy of
fuel.
Thirdly. The modes of forming a vacuum by means of the steam horn,
and also the high-pressure water horn.
Fourthly. The system of cooling the alembic or boiler at the end of
the concentrating operation, that is, when the heat accumulated in the
furnace would endanger the melting of the lead if no other water were
used.
And fifthly. The application of the hollow porcelain, stone, or earthen-
ware boxes to sustain the interiors of the walls of the leaden reservoirs
when pumping, by means of my steam or high-pressure water horns,
sulphuric acid, and other corrosive liquids, as all such improvements
are herein described and illustrated in the accompanying Sheet of
Drawings.
In witness whereof, I, the said Auguste Ferdinand de Hemptinne,
have hereunto set my hand and seal, this Third day of May in
the year of our Lord One thousand eight hundred and seventy-
one.