Improvements in and Apparatus for the Manufacture of Sulphuric Anhydride.
Year: 1898

page_text: Date of Application, 21st July, 1898
Complete Specification Left, 20th May, 1899-Accepted, 21st July, 1899
PROVISIONAL SPECIFICATION.
Improvements in and Apparatus for the Manufacture of Sulphuric
Anhydride.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by The Badische Anilin & Soda Fabrik, of
Ludwigshafen-on-Rhine in the German Empire) to be as follows: -
It is well known that when sulphur dioxide is combined with oxygen to form
sulphuric anhydride, a considerable amount of heat is evolved. This is stated in
literature to be in accordance with the equation SO₂ + 0 = SO, + 32, 2 Cal.
(See Hess. Poggendorff's Annalen, Vol. 56, p. 471, 1842. Thomsen Poggendorff's
Annalen Vol 150 p. 32, (1873) Ostwald, Allgem Chemie Vol. II pp. 123 & 124.
The reaction between 80, and 0 only takes place at an elevated temperature, so
that it is necessary to submit the gases, either separately, or in admixture to a
preliminary heating. During the reaction the heat of chemical union becomes
added to that applied and thus the temperature may rise to an enormous degree.
even to bright red heat, according to the richness of the gas mixture in sulphur-
dioxyde or the strength of the current of the gases.
My foreign correspondents have found that this accumulation of heat and rise
of temperature is very injurious when practically manufacturing sulphuric
anhydride. The injurious effects are of various kinds. For instance, the iron
parts of the apparatus are quickly destroyed by oxydation the action of the
contact substance employed for promoting, or inducing the reaction is weakened,
the efficiency of the apparatus is diminished, and the course of the reaction which
should be approximately quantitative, becomes essentially less perfect.
The overheating is especially injurious if the arrangement of the apparatus be
such that the mixture of gases containing the SO3 leaves the contact-mass at the
point where it has the highest temperature.
My foreign correspondents have discovered that this deterioration in the course
of reaction is due to the fact that the reconversion of $0, into SO2 + 0 takes
place at temperatures which are but little higher than those at which the forma-
tion of $0 proceeds most favourably whilst, at the same time the union of
SO, and takes place very much more rapidly in the first portions of
the contact mass than in those following so that the whole apparatus from the
beginning attains too high a temperature.
The reversal of the reaction increases in amount the more the contact-apparatus
becomes over-heated by the afore-mentioned excess of heat, that is, accordingly as
more gases or more concentrated gas mixtures, pass through the contact apparatus
Consequently it is impossible to effect any satisfactory union of sulphuric dioxide
and oxygen, or some of the sulphuric anhydride formed is decomposed in the
reverse direction. The gases leaving the apparatus therefore contain unchanged

page_text: sulphur dioxide which can only be used in other ways, if at all, such as for the
manufacture of sulphuric acid according to the chamber process or the manu-
facture of bisulphite or the like.
My foreign correspondents have invented a process and apparatus in which
it can be carried out which avoid the aforesaid disadvantages. The process
according to this invention consists in cooling the contact-mass by suitably
regulated external cooling whereby the injurious excess of heat is withdrawn.
In this way a condition of temperature in the contact-apparatus is attained which
is within wide limits independant of the quantity and concentration of the gas
treated, and which includes the most favourable temperature for the formation
of SO. By the process according to this invention it is possible to obtain a
practically quantitative yield of sulphuric anhydride, to a degree comparable with
the action in the sulphuric acid chambers further the contact-mass, and the
apparatus generally are more durable owing to. the lower temperature to which
they are subjected and their efficiency is largely increased.
The manner of practising the process according to this invention can be varied
in many respects, in particular, regard must be had to the concentration of the
gases to be treated.
.
The cooling of the contact-chamber so as to produce the most favourable. range
of temperature therein is generally effected by means of a current of gas. Both
the rate of flow and the temperature of this current are kept under control. My
foreign correspondents use for instance, air in this way or the actual gases which
are to be treated. But the cooling can be effected in other ways for instance in
liquid baths especially molten metal baths, whose temperatures are under control.
When the gases to be treated are themselves used for cooling the contact-
apparatus a part or the whole of the current of gases so to be treated is caused
to pass through the space exterior to the chamber containing the contact mass
as to withdraw from the latter the excess of heat. The gases coming from the
cooling chamber are then brought to the temperature best suited for the most
favorable course of the reaction. For this purpose in some cases a further
heating or a cooling operation is necessary; this depends largely upon the con-
centration of the gases.
So
I will now describe apparatus in various forms suitable to the purposes of this
invention.
In a brickwork structure or an iron tube is fixed a second tube consisting of
two parts which have different functions and may differ from one another in
length and diameter and either part or both parts can be replaced by a plurality
of tubes. The one part of the said tube is occupied by the contact substance and
this is cooled by cold air entering at the lower end of the outer structure or tube.
In the other part of the aforesaid inner tube the gases containing the sulphur
dioxide which enter at the upper end thereof are heated to the temperature
necessary for the reaction.
When commencing the operation the whole apparatus is first raised to the
temperature necessary for the reaction by heating by means of gas flames or
otherwise. Then, when concentrated gases are used after the reaction has once
commenced further heating is unnecessary, because the air cooling the contact
mass absorbs heat and transfers sufficient to the portion of the tube containing
the sulphur dioxide gases to prevent a change of position in the reaction zone, or
the entire cessation of the reaction. The stream of air can be regulated by means
of adjustable up-draught openings in such a way that the contact mass
constantly maintained at the most favourable temperature 'for the reaction.
When the gases contain but little sulphur dioxide the air which is somewhat
heated by its cooling action is further heated by means such that the gases
flowing in through the part of the tube therefor receive a greater increment of
heat. When the gases are still poorer in SO, it may be necessary to continually
heat to some extent by means of the gas flames or otherwise, the current of
air flowing into the outer structure or tube.
is

page_text: The gases, containing, the sulphuric, anhydride issuing from the contact mass
leave the apparatus by a pipe and are worked up in any suitable way.
When the apparatus is made up of a plurality of contact tubes they can be
put in connection with one another by means of a tube plate and cover above
and below.
Another form of the apparatus is as follows:-
-
Within brickwork a tube is fixed which contains an inner tube passing through
tube plates above and below which close the space between the outer and. inner
tubes.
The apparatus is brought to reaction temperature by any source of heat such for
instance as gas flames between the brickwork and the outer, tube, the gases from
which flames can pass away through flues in the brickwork. Then the gases to
be treated are passed through entrance passages into the space between the
inner and outer tubes say at bottom or midway or both.
The temperature of this can be further regulated by a heating apparatus
through which the gases pass on their way to the said space. The said gases
cool the contact mass in the inner tube and pass into the contact mass in the
inner tube and out by the lower end of the said tube. The temperature of the
gases can also be regulated by passing through a temperature regulator on their
way to the inner tube.
This apparatus also can have a plurality of tubes and my foreign correspondents
have found that in large apparatus containing many tubes it is advisable that
the current of gases in the outer tube or chamber be thoroughly sub-divided.
This can be effected by gas chambers surrounding the said outer-tube or chamber,
openings serving to introduce the gases into the said outer tube or chamber around
its entire circumference and further by the use of tubes passing diametrically
through the said outer tube or chamber and furnished with holes at the sides
varying in size in proportion to the part of the apparatus at which they occur,
the gases are divided uniformly in the interior of the said tube or chamber.
In order that the cooling gases may retain the direction of their current and
pass as closely as possible in contact with the contact mass there are inserted at
intervals which must not be too great, a number of partitions extending across
the said tube or chamber sufficient space being left for the gases to pass through
close to the walls of the inner tubes.
It is desirable to thoroughly mix the gases before their entrance into the contact
mass in order to equalize their temperature. This can be effected by a mixing
apparatus fitted in the cover. The strength of the current and the temperature of
the cooling gases is regulated upon the basis of the readings of the thermometers
in the various parts of the apparatus and to such an extent that analyses of the
gases entering and leaving the apparatus shew that the most favourable practical
result is being obtained.
In this apparatus also air or other gas can be used for cooling and be passed
in by a ventilator or fan it of course not being permitted to enter the inner tube
or tubes....
The heat of the air or gas issuing from the apparatus can be utilized in any
way desired for. instance by transferring its heat in an interchanger to the cold
gases to be treated.
The following is an arrangement of the apparatus which is particularly suited
for use when treating rich gas mixtures. The entering gas current is lead to the
part surrounding the hottest part of the contact mass in the inner tube so that
the relatively coldest gas acts upon the hottest part of the contact mass and
energetically cools this. The cooling gas current can leave the cooling chamber
through parts arranged similarly to those herein before described for admittance
in the preceding example and can then be conducted either directly to the inner
tube or tubes or through a temperature-regulating apparatus. Also a portion of
the gas can be led at the same time directly into the cover and thence into the
inner tubes.
Here also the regulation of the gas currents is based upon gas analyses and the

page_text: readings of thermometers and here also air or other gas instead of the gases to be
treated can be used for cooling. This is especially desirable when rich gases are
to be treated for their volume and quantity are comparatively small and might not
be sufficient to cool efficiently. For this purpose the cooling current of air or gas
is created by a fan or ventilator and passed to the part surrounding the hottest part
of the contact mass and streams through the surrounding tube and cools the contact
mass and then leaves the apparatus. The heat contained therein can be used in
any way desired for instance for heating up the entering gases to be treated so
that the reaction zone in the inner tube does not change its position. Or the
apparatus may be arranged as follows: In a brickwork passage or tube, a tube
or several tubes closed at bottom is or are suspended from a plate which closes
it or them above and into this tube or each of these tubes projects a tube fitted
into the said plate. When a plurality of tubes is used the inner and outer tubes
are separated from one another by a box-like chamber the interior of which serves
for the sub-division of the entering gases. The gases stream through the space
between the inner and outer tubes and cool the contact mass in the inner tube
or tubes. They can be heated further by gas flames below the lower ends of the
outer tubes or otherwise or be cooled for example by a regulated stream of air.
The treated gases leave the apparatus through a cover and outlet over the upper
end of the inner tube or tubes.
Having described various forms of the apparatus and ways of carrying out
the process. I will now describe what I believe to be the best manner of pro-
ceeding in order to obtain as favourable a result as possible.
Taking the case of a mixture of gases such as frequently occurs containing
about twelve per cent. by volume of sulphur dioxide and a similar quantity of
oxygen and an apparatus with a plurality of tubes as described under the preced-
ing second example of the apparatus. The apparatus is heated first say by means
of gas flames until a thermometer in the upper cover shews a temperature of
about 300 Centigrade. The entire stream of gases is then passed into the appara-
tus. The gases entering and leaving the apparatus are analysed to determine their
contents of sulphur dioxide and in this way the practical effect is determined.
The temperature in the interior of the contact apparatus is regulated on the
basis of the readings of the thermometers in the upper and lower covers by regu-
lating the intensity of current of the cooling stream of gases by means of valves
and the temperature if necessary by the aid of the heater that the most favorable
conversion of SO, into SO, is achieved.
In this example this object is achieved by passing about two thirds of the
entire gas current in at the entrance to the chamber surrounding the inner tubes
and one third direct into the top cover, so that the temperature therein (which
becomes uniform owing to the action of the mixing-chamber in the said cover) is
about 380° Centigrade whilst the thermometer in the lower cover indicates
about 234° Centigrade. In this actual case taken from experimental practice
on the factory scale my foreign correspondents effected a conversion of from
96 to 98 per cent. of that theoretically possible, whilst making from 40 to 50 kilo-
grams of SO, per tube in twenty-four hours. The conversion can be increased to
99 per cent. if the gas be permitted to remain longer in the presence of the contact-
substance.
Dated this 91st law of Tu1.. 1000
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C.,
Agents.

page_text: Improvements in and Apparatus for the Manufacture of Sulphuric
Anhydride.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the The Badische Anilin & Soda Fabrik, of
Ludwigshafen-on-Rhine, in the German Empire) and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:
-
It is well known that, when sulphur dioxide is combined with oxygen to form
sulphuric anhydride, a considerable amount of heat is evolved. This is stated in
literature to be in accordance with the equation SO, + 0 = SO3 + 32, 2 Cal.
(see Hess Poggendorff's Annalen Vol. 56, p. 471, 1842; Thomsen Ann. ch. ph. (4)
Vol. 30 p. 422, 1873 Ostwald Allgemeine Chemie, Vol II p.p. 123 and 124). The
reaction between SO, and O only takes place at an elevated temperature, so that
it is necessary to submit the gases, either separately, or in admixture, to a pre-
liminary heating. During the reaction the heat of chemical union becomes added
to that applied, and thus the temperature may rise to an enormous degree, even
to bright red heat, according to the richness of the gas mixture in sulphur-
dioxide, or the strength of the current of the gases.
My foreign correspondents have found that this accumulation of heat and rise
of temperature is very injurious when practically manufacturing sulphuric
anhydride. The injurious effects are of various kinds. For instance, the iron
parts of the apparatus are quickly destroyed by oxidation, the action of the
contact-substance employed for promoting, or inducing, the reaction is weakened,
the efficiency of the apparatus is diminished, and the course of the reaction, which
should be approximately quantitative, becomes essentially less perfect.
The overheating is especially injurious if the arrangement of the apparatus be
such that the mixture of gases containing the SO, leaves the contact-mass at the
point where it has the highest temperature.
My foreign correspondents have discovered that this deterioration in the course
of the reaction is due to the fact that the reconversion of SO, into SO, + O takes
place at temperatures which are but little higher than those at which the forma-
tion of SO proceeds most favourably, whilst, at the same time, the union of
SO, and takes place very much more rapidly in the first portions of
the contact-mass than in those following, so that the whole apparatus, from the
beginning, attains too high a temperature.
The reversal of the reaction increases in amount the more the contact-apparatus
becomes over-heated by the afore-mentioned excess of heat, that is, accordingly as
more gases, or more concentrated gas mixtures pass through the contact-apparatus.
Consequently it is impossible to effect any satisfactory union of sulphur dioxide
and oxygen, or some of the sulphuric anhydride formed is decomposed in the
reverse direction. The gases leaving the apparatus therefore contain unchanged
sulphur dioxide which can only be used in other ways, if at all, such as for the
manufacture of sulphuric acid according to the chamber process, or the manu-
facture of bisulphite, or the like.
My foreign correspondents have devised a process, and apparatus in which
the said process can be carried out, by which the aforesaid disadvantages are
avoided. In this process platinized asbestos is the contact substance recommended
for use.
It can for instance be prepared as described in the Specification of
Winkler's German Patent No. 4566; see also Lunge's "Sulphuric Acid & Alkali "

page_text: 2nd Edition Vol. 1, p. 863 and Dammer, Chemische Technologie, Vol. 1, p. 189.
The process, according to this invention, consists in cooling the contact-mass by
suitably regulated external cooling, whereby the injurious excess of heat is with-
drawn. In this way a condition of temperature in the contact-apparatus is attained
which is, within wide limits, independant of the quantity and concentration of the
gas treated, and which includes the most favourable temperature for the formation
of SO. By the process according to this invention it is possible to obtain a
practically quantitative yield of sulphuric anhydride, to a degree comparable with
the action in the sulphuric acid chambers; further, the contact-mass, and the
apparatus generally, are more durable, owing to the lower temperature to which
they are subjected, and their efficiency is largely increased.
The manner of practising the process according to this invention can be varied
in many respects, in particular, regard must be had to the concentration of the
gases to be treated.
•
The cooling of the contact-chamber so as to produce the most favourable range
of temperature therein is generally effected by means of a current of gas. Both
the rate of flow and the temperature of this current are kept under control. My
foreign correspondents use, for instance, air in this way, or the actual gases which
are to be treated. But the cooling can be effected in other ways, for instance, in
liquid baths, especially molten metal baths, whose temperatures are under control.
When the gases to be treated are themselves used for cooling the contact-
apparatus, a part, or the whole, of the current of gases so to be treated is caused
to pass through the space-exterior to the chamber containing the contact-mass, so
as to withdraw from the latter the excess of heat. The gases coming from the
cooling chamber are then brought to the temperature best suited for the most
favourable course of the reaction. For this purpose, in some cases, a further
heating, or a cooling, operation is necessary, this depends largely upon the con-
centration of the gases.
I will now describe with reference to the accompanying drawings apparatus, in
various forms, suitable to the purposes of this invention. I refer first to Figure I
which is a vertical section.
In a brickwork structure, or an iron tube, M, is fixed a tube R leaving a space
between the outside of the tube R and the inside of the brickwork or tube, M.
The two portions a and b of the tube R have different functions, and may differ
from one another in length and diameter, and either part, or both parts, can be
replaced by a plurality of tubes. The one part 6 of the said tube R, is occupied
by the contact-substance, (indicated by the crossed lines) and this is cooled by cold
air entering by the inlets n at the lower end of the outer structure, or tube. In
the other part a, of the aforesaid inner tube, the gases containing the sulphur
dioxide which enter at the upper end thereof, are heated to the temperature
necessary for the reaction.
When commencing the operation the whole apparatus is first raised to the
temperature necessary for the reaction by heating by means of gas flames h, or
otherwise. Then, when concentrated gases are used, after the reaction has once
commenced, further heating is unnecessary, because the air cooling the contact-
mass absorbs heat and transfers sufficient heat to the other portion a of the tube
containing the sulphur dioxide gases to be treated to prevent a change of position
in the reaction zone, or the entire cessation of the reaction. The stream of air
can be regulated by means of adjustable up-draught openings L, in such a way
that the contact-mass in the part 6 is constantly maintained at the temperature
most favourable for the reaction.
When the gases contain but little sulphur dioxide the air, which is somewhat
heated by its cooling action, is further heated by means of the gas flames h¹, h¹,
or in other manner, so that the gases flowing in through the part of the
tube receive a greater increment of heat. When the gases are still poorer in SO,
it may be necessary to continually heat the curent of air flowing into the outer
structure, or tube, to some extent, by means of the gas flames at h h or otherwise.

page_text: The gases containing the sulphuric anhydride issuing from the contact-mass
in the part b, leave the apparatus by a pipe c and can be worked up in any
suitable way.
Figure I shews in vertical section an arrangement wherein the apparatus is
made up of a plurality of contact-tubes R R put in communication with one
another by means of tube plates W, WI, and covers D, D' above and below.
The parts which correspond with those shewn in Figure 1 are marked with the
same letters of reference.
Another form of the apparatus is illustrated in elevation, partly in section, in
Figure II.
Within the brickwork, or tube, M, a tube S, is fixed which contains an inner
tube A passing through tube plates W and Wi above and below which close the
spaces between the said tubes.
The apparatus is brought to reaction temperature by any source of heat, such,
for instance, as gas flames at h between the brickwork or tube M, and the tube S,
the gases from which flames can pass away through flues at L. When the apparatus
is working the source of heat can usually be removed and cold air be allowed
to circulate through the space between the brickwork, or tube, M, and the tube S
thus contributing to the cooling of the whole apparatus. The gases to be treated
are passed through entrance passages into the space between the tubes, S and R
say at bottom E or midway E or both. The temperature of these can be further
regulated by a heating apparatus G through which the gases pass on their way
to the said space. The said gases cool the contact-mass in the inner tube R and
afterwards pass through A and F into the said contact-mass and out through c
at the lower end of the said tube R. The temperature of the gases can also be
regulated by their passing through a temperature regulator H, on their way from
the space between the tubes S and R to the inner tube R by manipulating the
valves as shewn for the purpose.
This apparatus also can have a plurality of tubes R as illustrated in Figure II*
and my foreign correspondents have found that, in large apparatus containing
many tubes, it is advisable that the current of gases in the outer tube, or
chamber, S, be thoroughly subdivided. This can be effected by means of gas
chambers A. A surrounding the said outer tube or chamber S the gases passing from
the said chambers A. A' into the said outer tube, or chamber, S, through openings
around its circumference; or by means of tubes B, B¹, passing diametrically
through the said outer tube or chamber, S, and furnished with holes at the sides
varying in size in proportion to the part of the apparatus at which they occur,
so that the gases are divided and pass uniformly into the interior of the said tube
or chamber S.
In order that the cooling gases may retain the direction of their current and
pass as closely as possible in contact with the walls of the tubes R containing
the contact-mass, there are inserted, at intervals which must not be too great,
a number of partition's C, C, extending across the said tube, or chamber, S, suffi-
cient space being left for the gases to pass through close to the walls of the inner
tubes R R as indicated by the small arrows.
It is desirable to thoroughly mix the gases before their entrance into the
contact-mass, in order to equalize their temperature. This can be effected by a
mixing apparatus N fitted in the cover ) the gases passing up the passages 0, F,
and between the plates as shewn. The strength of the current and the temperature
of the cooling gases is regulated upon the basis of the readings of the thermometers:
in the various parts of the apparatus especially within the covers D and D¹ and to
such an extent that analyses of the gases, entering and leaving the apparatus,
shew that the most favourable practical result is being obtained.
Figure II illustrates a form of apparatus in which the gas distribution cham-
hers (corresponding to those marked A A' in Figure II^) are extended to form a
jacket A to the whole apparatus, thus útilizing the radiant heat of the apparatus.

page_text: to heat the cooling gases. The said jacket is shewn as being provided with
plates for giving a circuitous course to the gases.
In this apparatus also air, or other gas, can be used for cooling, and be passed
in by a fan the said air, or gas, of course not being permitted to enter the inner
tube, or tubes, R. Thus in the form of apparatus shewn in Figure II the air,
could be blown by means of the fan V in through the heater G and out through
the interchanger H.
The heat of the air, or gas, issuing from the apparatus can be utilized in any
way for which such a source of heat is suitable, as, for instance, by transferring its
heat, in the said interchanger H, to the cold gases to be treated and entering
through J.
Or
Figures III and III illustrate an arrangement of the apparatus which is
particularly suited for use when treating rich gas mixtures. The entering gas
current is led through E F to the part surrounding the hottest part P of the
contact-mass in the inner tube R so that the relatively coldest gas acts upon the
hottest part of the contact-mass and energetically cools this. The cooling gas
current can leave the cooling chamber S, through pipes A, A¹, arranged similarly
to those shewn at E E for admittance in the preceding example, and can then be
conducted, either directly by the pipe 0 to the inner tube, or tubes, or through
a temperature regulating apparatus H by manipulating the valves shewn.
the gas can be led partly directly into the inner tube or tubes R and partly
through the regulating apparatus. J is a passage directly to the inner tubes R.
Here also the regulation of the gas currents is based upon gas analyses and the
readings of thermometers, and here also air, or other gas, instead of the gases to
be treated, can be used for cooling. This is especially desirable when rich gases
are to be treated, because their volume and quantity are comparatively small
and might not be sufficient to cool efficiently. For this purpose the cooling
current of air, or gas, is created by a fan Vi as shewn in Figure III and passed
through E to the part surrounding the hottest part P of the contact-mass and
streams through the surrounding tube S and cools the contact-mass and then
leaves the apparatus. The heat contained therein can be used in anyway desired,
for instance, for heating up the entering gases to be treated so that the reaction
zone at P in the inner tube R does not change its position. Or the apparatus
may be arranged as shewn in Figures IV and IV.
In a brickwork passage, or tube, M, a tube, or several tubes, S, closed at
bottom, is, or are, suspended from a plate W, which closes it, or them, above
as shewn in Figure IV and into this tube, or each of these tubes, projects a tube
fitted into the said plate. When a plurality of tubes is used the upper ends of the
inner tubes R, extend above the upper ends of the outer tubes S and are
surrounded by a box-like chamber K, the interior of which serves for the sub-
division of the entering-gases. The gases entering at E stream through the
space between the tubes R and S, and cool the contact-mass in the inner tube, or
tubes, R. They can be further heated by the gas flames h, below the lower ends
of the tubes S, or otherwise, or be cooled, for example by a regulated stream of air
passing out at L. The gases pass up through the contact mass in the tube
or tubes R and the treated gases leave the apparatus through a cover D and
outlet cover the upper end of the said tube, or tubes.
Having described various forms of the apparatus and ways of carrying out
the process I will now describe what I believe to be the best manner of proceeding
in order to obtain as favourable a result as possible, taking the case of a mixture
of gases, containing about twelve per cent., by volume, of sulphur dioxide, and a
similar quantity of oxygen, and an apparatus with a plurality of tubes as herein-
described and illustrated by Figure II. The apparatus is heated first (say by
means of gas flames or fire heat at h¹) until a thermometer in the upper cover D
indicates a temperature of about 300° Centigrade. Then the source of heat is
removed, and the whole gas stream passed into the apparatus at A. The tem-
perature within the cover D first rises. When it has reached a temperature

page_text: favourable for the reaction the upper valve V is opened, so that a part of the
gases enter directly through J. The gases entering and leaving the apparatus are
analysed to determine their contents of sulphur dioxide and, in this way, the
practical effect is determined. The temperature in the interior of the contact-
apparatus is regulated on the basis of the readings of the thermometers in the
upper and lower covers D), D', by regulating the intensity of current of the
cooling stream of gases by means of the valves V, VI and VI and the temperature,
if necessary, by the aid of the heater G, so that the most favourable conversion
of SO, into SO, is achieved.
In this example this object is achieved by passing about two thirds of the entire
gas-current in at the entrance A to the chamber S surrounding the inner tubes R
and one third directly into the top cover D, so that the temperature which becomes
uniform owing to the action of the mixing-chamber N, in the said cover, is about
380° Centigrade, whilst the thermometer in the lower cover D¹ indicates about
234° Centigrade. In this actual case, taken from experimental practice on the
factory scale by my foreign correspondents they have effected a conversion of
from 96 to 98 per cent. of that theoretically possible, whilst making from 40 to
50 kilograms of SO, per tube in twenty-four hours. The conversion can be
increased to 99 per cent. if the gas be permitted to remain longer in the presence
of the contact substance.
In the drawings accompanying this Specification the scale may be taken
as being one twentieth real size, but, of course, the size of the tubes and the
relative sizes of the various parts can be varied without departure from the nature
of the invention.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The improvement in the manufacture of sulphuric anhydride by the contact-
process, consisting in subjecting the contact-mass to a regulated cooling so as to
remove the excess of heat due to the reaction.
2. The several arrangements or constructions of apparatus substantially as
hereinbefore described and severally illustrated in the various figures of the
accompanying drawings for the purposes hereinbefore explained.
Dated this th day of Alax 1899
Dated this with day of Nax
899
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.