APPARATUS FOR CONCENTRATING SULPHURIC ACID
Year: 1884

page_text: I ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex
Engineer do hereby declare the nature of the said invention for "APPARATUS FOR
CONCENTRATING SULPHURIC ACID " to be as follows:-
This invention relates to improvements in apparatus for concentrating sulphuric
acid to produce oil of vitriol in which the sulphuric acid is subjected to heat in
platinum boilers. Heretofore all such boilers that have been in practical use have been
constructed either with a large platinum boiler, or with a platinum dish with leaden
water dome as shown in the United States lettors patent granted to Faure & Kessler
No 158,924 dated January 19. 1875 and modifications thereof. The gas produced
from the sulphuric acid in the platinum dishes of Faure & Kessler being condensed
under the water dome above the stills allowed the upper surface of the acid to be
cooled, while the lower surface was heated to the highest possible degree thus
greatly limiting the amount of oil of vitriol produced per square inch of heating
surface.
The great diameter of the platinum dishes in all apparatus heretofore used made
it necessary to use very heavy platinum prepared by the expensive process of
hammering in order to support the weight of the acid contained therein and the
large size of these dishes and the said unavoidable cooling under the water dome
required a large amount of fuel to heat the acid.
The objects of this invention are first, by the shape position and connections of
the boiler to allow the acid to be more rapidly and easily and more highly heated;
second to condense the gas away from the place where the acid is heated so that
comparatively little cooling action takes place upon the upper surface of the acid,
third to produce more oil of vitriol per square inch of heating surface; fourth by the
shape and construction of the boilers to allow the use of much lighter platinum and
of rolled instead of hammered platinum, thus greatly reducing the cost; fifth to
reduce the amount of fuel per pound of oil of vitriol produced; sixth to reduce
the size of the apparatus and thus the cost of the lead and brick plant in the
construction of the apparatus; seventh to reduce the loss of platinum through
action of the heat and acid these objects are attained by the apparatus hereinafter
described.

page_text: The furnace is constructed as usual in apparatus for this purpose although it
may be of much smaller dimensions than heretofore.
The heat from the same passes through an inclined shaft and wraps the lower
surface of the platinum boiler or boilers and thence passes under a leaden pan so as
to heat the acid up to a certain point before it passes into the platinum stills.
This leaden pan containing the supply of sulphuric acid, is constructed in the
usual manner and from it the acid is drawn by means of a regulating syphon into
a leaden boot or receiver from which it flows into a platinum funnel and thence
through the supply pipe into the first boiler of a series of platinum boilers formed
and connected and supported in a peculiar manner.
They consist of a horizontal platinum tube or preferably a series of horizontal
platinum tubes at the top of the furnace and shaft and arranged preferably in
descending order toward the furnace so that the acid will flow from each into the
one next below it by means of platinum overflow pipes which are preferably placed
at alternate ends of the platinum tubes or boilers; said pipes being preferably so
arranged that the surface acid of an upper or preceding tube will be carried to the
bottom of the tube next below it.
This method of connection has been found by experiment to create more rapid
evaporation of gases than any other, and consequently it makes the apparatus more
productive. The depth of acid in the first or highest of the tubes or boilers should
be less than in the next succeeding and the depth should become greater in each in
turn, for the reason that the acid being weaker in the first will reach boiling point
at a lower degree of temperature and therefore less acid should be allowed to
remain in the tube.
This construction will prevent the ebullition from overflowing the pipe for the
escape of gases
hereinafter described. The connecting or overflow pipes should be
made in sections so that any one tube or boiler can be easily removed and another
substituted if repairs are necessary. This is one of the chief advantages of the
descending series of tubes; for when arranged thus, the connecting tubes may each
contain a nicely constructed slip-joint which would not be possible without breakage
if the tubes were on the same level.
By the use of these horizontal tubular boilers the shape of which may be varied
a great saving is effected by reducing the loss of platinum caused by exposure to
heat upon one side and to acid upon the other. The tubes or boilers work well
when arranged on the same level, and they may be arranged lengthwise with the
shaft of the furnaco or at any intermediate anglo of inclination provided that ench
is substantially horizontal the descending series is however preferred in order that
the difference of acid level may be maintained and that the tubes may be made
removable by slip joints.
The series of tubes may be extended to any desired length the number being
limited only by the size of the fire space in the furnace and the amount of
production. A single tube constructed as described and especially if arranged.
lengthwise with the flue of the furnace would be far more productive and economical
than any of the apparatus heretofore used: but it would be far less productive or
economical than the series of tubes for the greater the number of tubes or the
greater the length of the tubes the greater will be the amount of surface exposed
to the heat of the furnace and so much greater will be the amount of acid
flowing through the tubes, and the amount of production of oil of vitriol. Henco
with an increased number of tubes the size of the pipes connecting them must
be increased.
From the last of the series of boilers the acid passes by means of a platinum
pipe into a cooler which is constructed in any ordinary manner preferably with a
coil of leaden pipe through which cold water passes.
The platinum boilers or tubes have gas openings at their tops preferably in the
centre through which the gas produced in each passes through platinum pipes to
leaden water arins in which and in leaden condensers attached it is condensed in

page_text: the usual manner The pipes leading to the water-arms are preferably furnished
with flaring mouths at the junction with the platinum tube or boiler.
Very weak sulphuric acid gas being produced from the boilers containing the
weak acid it is of little value, and hence for economy of space the first two water-
ways and perhaps more in a long series of boilers may be connected with one
condenser but the pipes & lending from the other boilers forming the latter or
lower half of the series and containing strong acid, and giving off strong sulphuric
acid gas, should never be connected with any of the pipes of the earlier or upper
half of the series, and the pipe of the last or lowest boiler must never be connected
with any other pipe for the reason that the tests are made upon the acid condensed
from the gas produced by this boiler for regulating the flow of acid into the
apparatus from the regulating syphon.
The connecting pipes may be of glass connected with the boilers and condensers
by hydraulic joints, but platinum is much better.
The construction of the water arms is as follows.-There is an outer casing of
wood without top, containing the water and an inner closed condenser of lead
surmounted by the water.
The connecting pipes are connected with the leaden casing of each water way by
a hydraulic joint projecting above the water and from the other end of the casing
projects a leaden pipe leading to the condenser This also being connected by a
hydraulic joint. The condensers may all be in one water box. Both the water
arms and the water box receive a constant supply of cold water. At the further
extremity of each condenser are two openings at the top for the exit of gases that
have not been condensed by the cooling process, and another at the bottom through
which the sulphuric acid passes to a proper receptacle.
The boilers are supported above the furnace and shaft by vertical iron plates
forming the upper portion of the sides of the furnace and shaft; said plates should
be formed to fit the shape of the tubes. Thus the ends of the cylindrical tubes
forming the boilers project beyond the direct heat of the furnace and hence the fine
gold solder with which the ends are united to the cylindrical sides of the tubes as
well as the fine gold solder with which the connecting pipes are united to them
will be in no danger of fusion from the heat, these parts being all outside the flue.
The tubes or boilers are above the acid level protected from the flames by pieces of
cast iron filling the space between adjoining tubes and extending from the-level of
the bottom of the overflow pipe in the upper tube to the level of the bottoin
of the overflow pipe in the lower tube. This construction allows the flames to
strike the entire surface of the platinum up to the acid level but prevents them
from striking the tubes above the acid level. Hence the greatest amount of boiling
surface is obtained for the acid and no heating surface whatever for the gas above it.
This construction greatly increases the producing power of the apparatus.
Dated this 24th day of June 1884.

page_text: COMPLETE SPECIFICATION,
CONCENTRATING SULPHURIC ACID
"
I ALFRED JULIUS BOULT of 323 High Holborn in the county of Middlesex
Engineer do hereby declare the nature of this invention for "APPARATUS FOR
A communication from Marinus Willett of
Newport, Rhode Island, United States, Gentleman and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement :-
This Invention relates to improvements in apparatus for concentrating Sulphuric
acid to produce Oil of Vitriol in which the Sulphuric acid is subjected to heat in
platinum boilers-Heretofore all such boilers that have been in practical uso have
been constructed either with a large platinum boiler or with a platinum dish with
leaden water domo as shown in the United States Letters Patent granted to
Faure & Kessler N° 158,924 dated January 19th 1875 and modifications thereof.
The gas produced from the Sulphuric acid in the platinum dishes of Faure &
Kossler being condensed under the water dome above the stills allowed the upper
surface of the acid to be cooled while the lower surface was heated to the highest
possible degree thus greatly limiting the amount of oil vitriol produced per square
inch of heating surface.
The great diameter of the platinum dishes in all apparatus heretofore used made
it necessary to use very heavy platinum prepared by the expensive process of
hammering in order to support the weight of tho acid contained therein and the
large size of these dishes and the said unavoidable cooling-under the water dome
required a large amount of fuel to heat tho acid.
The objects of this invention are first, by the shape position and connections of
the boiler to allow the acid to be more rapidly and easily and more highly heated ;
second, to condense the gas away from the place where the acid is heated so that
comparatively little cooling action takes place upon the upper surface of the acid;
third, to produce more oil of vitriol per square inch of heating surface; fourth, by
the shape and construction of the boilers to allow the use of much lighter platinum
and of rolled instead of hammered platinum thus greatly reducing the cost; fifth,
to reduce the amount of fuel per pound of oil of vitriol produced; sixth, to reduce
the size of the apparatus and thus the cost of the lead and brick plant in the con-
struction of the apparatus; seventh, to reduce the loss of platinum through action
of the heat and acid-These objects are attained by the apparatus illustrated in
the accompanying Drawings in which,
Figure 1 is a side view of the improved apparatus; Figure 2 is a view of the
same from above; Figure 3 is an end view of the apparatus showing one of the
improved boilers with its connections.
Similar letters refer to identical parts throughout the several views.
A is the furnace constructed as usual in apparatus for this purpose although it
may be of much smaller dimensions than heretofore-The heat from the same
passes through the inclined shaft a and wraps the lower surfaces of the platinum
boiler or boilers, and thence passes under the leaden pan B so as to heat the acid
up to a certain point before it passes into the platinum stills-This leaden pan B

page_text: containing the supply of Sulphuric acid, is constructed in the usual manner and
from it the acid is drawn by means of the regulating syphon C into the leaden
boot D from which it flows into the platinum funnel E and thence through the
supply pipe E into L which is the first of the series of platinum boilers.
LM NO are the boilers formed and connected and supported in the peculiar
manner by which the advantages of small cost of construction are attained com-
bined with great producing power-They consist of a horizontal platinum tube or
preferably a series of horizontal platinum tubes, at the top of the furnace A and
shaft a and arranged preferably in descending order toward the furnace A so that
the acid will flow from each into the one next below it by means of the platinum
overflow pipes l m n which are preferably placed at alternate ends of the platinum
tubes or boilers said pipes l m n being proferably so arranged that the surface
acid of an upper or preceding tube will be carried to the bottom of the tube next
below it as shown in Figure 1.
This method of connection has been found by experiment to create more rapid
evaporation of gases than any other, and consequently it makes the apparatus more
productive. The depth of acid in the first or highest of the tubes or boilers should
be less than in the next succeeding and the depth should become greater in each in
turn, for the reason that the acid being weaker in the first will reach boiling point
at a lower degree of temperature and therefore less acid should be allowed to
remain in the tube-This construction will prevent the ebullition from overflowing
the pipe S for the oscape of gases hereinafter described.
It has been found that the bottom of the escape pipe & leading from the first tube
or boiler L should be preferably about one inch and a half from the bottom of the
tube or boiler and that the bottom of the discharge pipe F leading from the last of
the series should be preferably about two and a half inches from the bottom of the
last tube or boiler and that the connecting pipe acting as the discharge from each
succeeding tube should be preferably higher than in the one preceding by a fraction
of an inch corresponding with the number of tubes in. use-This allows a greater
depth of acid in the tubes containing the stronger acid and subjected to the most
heat. The boiler containing the weakest acid will thus have a film of acid only
one and a half inches deep and the boiler containing the strongest acid will contain
a film of acid only two and a half inches deep.
The connecting pipes l. m. n should be made in sections so that any one tube or
boiler can be easily removed and another substituted if repairs are necessary-The
points are indicated at h. This is one of the chief advantages of the descending
series of tubes; for when arranged thus the connecting tubes l. m. n may each
contain a nicely constructed slip-joint h which would not be possible without
lenkage if the tubes were on the same level.
The size and form of these platinum tubes or boilers that have been found useful
is that of a cylinder six inches in diameter and three feet long though the invention
is not confined to these dimensions; nor to this shape.
The cross section may be oval or of any other convenient form.
In the construction of tubes of this sizo rolled platinum may be used instead of
the much heavier beaten platinum necessary for the dishes heretofore employed.
The reduction in the amount of this metal considerably decreases the cost of
constructing apparatus yielding a given quantity of Oil of Vitriol; and this
apparatus being much more compact there is also a great saving of brickwork in
building.
The producing capacity of this apparatus is much greater than that of Fauro &
Kesslers, the latter producing but eleven pounds of oil of vitriol per square inch
of heating surface whereas mine will produce from eighteen to twenty two pounds
per square inch.
By the use of these horizontal tubular boilers a great saving is effected by
reducing the loss of platinum caused by exposure to heat upon one side and to acid
upon the other-Some loss is inevitable; and in the old stills the loss of platinum
per ton of oil of vitriol produced was two grammes and in Faure & Kessler's

page_text: apparatus the loss was about three one hundredths (03) of a gramme per ton;
while in this apparatus on account of the small amount of platinum exposed in
proportion to the production, the loss of platinum per ton of oil of vitriol produced
will be greatly reduced below that of Faure & Kessler, namely, according to
estimates, to about six ten-thousandths (0006) of a gramme.
The tubes or boilers L M N. O. work well when arranged on the same level; and
they may be arranged lengthwise with the shaft a or at any intermediato anglo of
inclination provided that each is substantially horizontal, the descending series
shown in the drawings is however preferred in order that the difference of acid
level may be maintained and that the tubes may be made removeable by the slip
joints h.
The series of tubes may be extended to any desired length; the number being
limited only by the size of the fire space in the furnace and the amount of pro-
duction. A single tube constructed as shown and described and especially if
arranged lengthwise with the flue of the furnace would be far more productive and
economical than any of the apparatus heretofore used, but it would be far less
productive or economical than the series of tubes shown; for of course the greater
the number of tubes or the greater the length of the tubes the greater will be the
amount of surface exposed to the heat of the furnace and as much greater will be
the amount of acid flowing through the tubes and the amount of production of oil
of vitriol. Hence with an increased number of tubes the size of the pipes l. m. n.
connecting them must be increased. It is found that with a series of four tubes
as shown the best size of connecting pipe is about one inch inside measurement;
and that if six tubes are used an inch and a quarter pipe will be required. From
the last of the series O tho acid passes, by means of the platinum pipe F into the
cooler G which is constructed in any ordinary manner preferably with a coil of
leaden pipe through which cold water passes.
The platinum boilers or tubes L M. N. O. have gas openings at their tops
preferably in the centre through which the gas produced in each passes through the
platinum pipes S1 S2 S3 S* respectively to the leaden water arms Y¹ Y' 'Y' Y*
respectively in which and in the leaden condensers W W W³ attached it is
condensed in the usual manner-it is preferred to have these pipes S about two
inches in diameter and with a flaring mouth about three inches in diameter at the
junction with the platinum tube or boiler.
Very weak sulphuric acid gas being produced from the boilers containing the
weak acid it is of little value and hence for economy of space tho first two water-
ways Y Y and perhaps more in a long series of boilers may be connected with
one condenser Wi as shown in Figure 3, but the pipes S S &° leading from the
boilers O and N forming the latter or lower half of the series and containing strong
acid and giving off strong sulphuric acid gas, should never be connected with any
of the pipes of the earlier or upper half of the series; and the pipe S' of the last
or lowest boiler O must never be connected with any other pipe for the reason that
the tests are made upon the acid condensed from the gas produced by this boiler
for regulating the flow of acid into the apparatus from the regulating syphon C.
The pipes S may be of glass connected with the boilers and condensers by hydraulic
joints but platinum is much better.
The construction of one of the water arms Y is shown in detail in Figure 3;
b being the outer casing of wood without top containing the water and c being the
inner closed condenser of lead surrounded by the water.
The pipes S are connected with the leaden casing c of each water way Y by a
hydraulic joint y projecting above the water as shown in Figure 3 and from the
other end of the casing c projects the leaden pipe d to the condenser W, this also
being connected by a hydraulic joint f. The condensers W W W³ may all be in
one water box X as shown in Figure 3. Both the water arms Y and the water
box X receive a constant supply of cold water. At the further extremity of
ench condenser W are two openings at the top, not shown, for the exit of gases
that have not been condensed by the cooling process, and another at the bottom

page_text: represented by the pipe V through which passes to a proper receptacle the sulphuric
acid produced by tlie condensation.
The platinum tubes L M NO are supported above the furnace A and shaft a
by vertical iron plates T (Figure 1) forming the upper portion of the sides of the
furnace and shaft said plates should be formed to fit the shape of the tubes. Thus
the ends of the cylindrical tubes forming the boilers project beyond the direct heat
of the furnace as shown in Figures 1 and 3 and hence the fine gold solder with
which the ends are united to the cylindrical sides of the tubes as well as the fine
gold solder with which the connecting pipes l. m. n are united to them will be in
no danger of fusion from the heat, these parts being all outside the Bue. The tubes
or boilers above the acid level are protected from the flames by pieces of cast iron
(or other suitable material) R. R. (Figure 1) filling the space between adjoining
Lubes and extending from the level of the bottom of the overflow pipe in the upper
tube to the level of the bottom of the overflow pipe in the lower tube. This con-
struction allows the flames to strike the entire surface of the platinum up to the
acid level but prevents them from striking the tubes above the acid level. Henco
the greatest amount of boiling surface is obtained for the acid and no heating
surface whatever for the gas above it. This construction greatly increased the
producing power of the apparatus.
Prior to this invention apparatus for concentrating sulphuric acid have been
made with a series of platinum retorts 'arranged in a plane and connected together
by platinum so called syphon pipes which extend from the bottom of one retort to
a higher point of the next adjoining retort; said retorts being platinum dishes set
into the top of the furnace in the same manner as vessels are set in ordinary
cooking stoves and they are covered with conical platinum tops as shown in the
United States Letters Patent granted to Kolbe and Lindfors August 30th 1881
No 246,396. The apparatus shown in this Patent is designed to accomplish one
of the results secured by this invention namely, lessening the cost of the apparatus
But it does not greatly, if at all reduce the cost for the reason that the forms of the
platinum boilers shown would make them very expensive as they must be con-
structed of beaten platinum and probably a larger amount of platinum would bo
required to construct such apparatus than to construct one of the same producing
capacity under the Faure & Kessler Patent, because in the Kolbe & Lindfors Patent
a very small heating surface is exposed, and considerable depth of acid exists above
the heating surface owing to the improper form and position of the connections of
the retorts. Hence for the amount of platinum used there would be a very small
production as compared with that of this improved apparatus. I do not regard the
Patent No 246,396 as a practical improvement over the Faure & Kessler Patent or
as practically effecting any of the results of my invention.
In view of the series of retorts shown in this Patent, however, I do not claim
broadly the use of a series of platinum retorts connected together.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as cominunicated to
mo by my foreign correspondent I declare that what I claim is
1. In apparatus for concentrating sulphuric acid, the tube L in combination
with the gas escapo S supply pipe E' and discharge pipe substantially as
described.
2. In an apparatus for concentrating sulphuric acid a group of boilers as L, M.
N. O. arranged over a furnace in a descending series and connected and mounted
substantially as specified whereby the lower portions of the boilers are exposed to
the heat of the furnace substantially to an equal height on both sides as and for
the purpose set forth.
3. In apparatus for concentrating sulphuric acid the descending series of two or.
more platinum boilers connected together by platinum pipes each having the slip
5 joint substantially as described.
4. In an apparatus for concentrating sulphuric acid, a group of boilers arranged
over a furnace in a descending series, in combination with a series of plates between

page_text: the boilers having the lower portion of one plate in contact with the lowest boiler
of a pair of the series at the level of the liquid and its highest part in contact with
the highest boiler of the two, at the level of the liquid, substantially as described.
5. In apparatus for concentrating sulphuric acid the connected series of two or
more platinum tubes L M N. O. supported and protected at the top of the furnace A
by the plates T and R substantially as described.
6. In apparatus for concentrating sulphuric acid the descending series of two or
more tubular boilers L. M. N. O. having the acid level higher in each lower boiler
of the series than in the one preceding by means of the relative position of the
connecting pipes and discharge pipo F substantially as described.
7. In an apparatus for concentrating sulphuric acid in combination with a
descending series of horizontal tubular boilers as L. M. N. O. connected substantially
as described whereby a fixed fluid level is maintained in each, a plate, as R arranged
between each pair of boilers in the series, the lower end of said plate being joined
to the lower boiler at its fluid level, while its upper end is joined to the upper boiler
at its fluid level substantially as and for the purposes specified.
8. In apparatus for concentrating sulphuric acid a connected series of two or
more tubular boilers exposed to the direct heat of the furnace up to tho acid level,
and having the ends and connecting pipes protected from the direct heat by
projecting beyond the flue of the furnace substantially as described.
9. In apparatus for concentrating sulphuric acid a connected series of two or
more boiler tubes L M in combination with the furnaco A gas escape pipe S and
with a supply pipe El connected with the first of the series and the discharge pipe F
connected with the last of the series substantially as described.