IMPROVEMENTS RELATING TO, .THE. MANUFACTURE OF SULPHURIC ACID
Year: 1881

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS RELATING TO, .THE.
MANUFACTURE OF SULPHURIC ACID." A communication from abroad by
Frederic Benker and Henri Lasne, both of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
Office of the Commissioners of Patents on the 5th May 1881.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. " IMPROVE-
MENTS RELATING TO THE MANUFACTURE OF SULPHURIC ACID." A communication
from abroad by Frederic Benker and Henri Lasne, both of Paris, in the Republic
of France.
In the manufacture of sulphuric acid as at present ordinarily conducted the
gases from the chambers before being allowed to pass into the atmosphere are
made to traverse what is known as the Gay Lussac tower.
The Gay Lussac tower is a column packed with small lumps of coke, down
which concentrated sulphuric acid is kept trickling, and its function is to bring the
gases from the chambers into intimate contact with sulphuric acid of a certain
strength in order that such of the nitrous compounds contained in the chamber
gases as are capable of entering into chemical combination with sulphuric acid of
that strength may be absorbed thereby in order to be thereafter liberated therefrom
for use again.
=
The Gay Lussac tower thus effects a very important economy in the manufacture :
of sulphuric acid, but it does not absorb the whole of the nitrous compounds
contained in the gases from the chambers, and the chief reason of this is that a
large part of those compounds are in the state of nitric peroxide, which is a body
which cannot enter into chemical combination with sulphuric acid. Despite the.
Gay Lussac tower therefore it has not hitherto been possible to manufacture
sulphuric acid without losing nitrous compounds in such proportion as to involve a
consumption of at least from three to four parts of nitrate of soda per hundred
parts of sulphur burnt. The cost of this proportion of nitrate of soda is about
one-tenth of the total cost for materials of sulphuric acid manufactured from
pyrites.
The present Invention relates to a means of reducing this loss of nitrous
compounds to from one-half to one-third of its present amount. The said means
consists in transforming the nitric peroxide contained in the chamber gases into
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page_text: compounds absorbable by strong sulphuric acid by the chemical reaction upon the
said nitric peroxide of sulphurous acid gas, aided by vapour of water and free
oxygen, and the present Invention consists in introducing sulphurous acid gas for
this purpose into the gases from the chambers at such a point of the passage of
those gases from the chambers to the Gay Lussac tower as to permit that before
they reach the Gay Lussac tower the gases from the chambers, and the sulphurous
acid gas so added to them shall have mingled sufficiently to secure that on their
reaching the Gay Lussac the nitric peroxide of the chamber gases shall be absorbed
and retained as nitro-sulphonic acid, from which nitrous acid, for uso again, can
afterwards be liberated by well-known means. The sulphurous acid gas may be
either admitted into the pipe which conveys the exit-gases from the chambers to
the Gay Lussac tower, at a point sufficiently distant from the Gay Lussac tower
to permit of an approach to complete mixture before the gases reach the Gay
Lussac tower, or a special small chamber may be interposed between the present
chambers and the Gay Lussac tower, both the exit-gases from the present chambers
and the sulphuric acid gas which is to react on their nitric peroxide being made to
pass through this small special chamber before entering the Gay Lussac tower.
The sulphurous acid to be thus introduced into the gases coming from the
vitriol chambers may be taken from the pyrites burners or the sulphur burners, as
the case may be, or it may be generated in special apparatus, or may be taken from
the gases passing from the Glover tower. It may be either forced or aspirated by
whatever means may be preferred in each particular case, but the means employed
must be such as to permit that the quantity of sulphurous acid gas introduced into
the exit-gases from the chambers may be easily regulated at will. My corre-
spondents prefer to draw it from the apparatus in which it is produced and to
inject it into the exit gases from the vitriol chambers by means of an injector
on the same principle as the Körting injector, but made of an alloy of lead and
antimony.
The quantity of sulphurous acid gas to be introduced into the gases coming from
the vitriol chambers must be regulated by tests of the gases passing off from the
Gay Lussac tower. The necessary tests of these gases may most easily be made
by means of peroxide of lead paper. If wet peroxide of lead paper be decolourized
by the gases passing off from the Gay Lussac tower immediately on being immersed
in them, it will be because too much sulphurous acid gas is being added to the
gases from the vitriol chambers. . When sulphurous acid gas is being supplied to
the chamber gases in sufficient but not excessive proportion, the gases passing from
the Gay Lussac tower will not decolourize wet peroxide of lead paper in less than
from five to fifteen minutes, according to the rate at which those gases are travelling
in the conduit into which the test paper is introduced.
It will be well understood that in order to obtain the best possible results from
the present Invention the vitriol chambers must be so worked that the gases coming
from them shall contain free oxygen, preferably in the proportion of from five to
seven per cent., and that at least so much vapour of water should be present with
the mixture of gases formed by adding sulphurous acid gas to the chamber gases
as shall correspond to the quantity necessary for the transformation of all the
nitric peroxide in the chamber gases into nitrosulphonic acid.
Carefully worked this Invention reduces the loss of nitrous compounds in the
manufacture of sulphuric acid by the full amount of the quantity thereof, which at.
present escapes as nitric peroxide, and at the same time greatly increases the
quantity of sulphuric acid, which can be manufactured in chambers of a given cubic
capacity per unit of time.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, and of
an Order of the Lord Chancellor, filed by the said Walter Weldon in the Great
Seal Patent Office on the 12th November 1881.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. "IMPROVE-
MENTS RELATING TO THE MANUFACTURE OF SULPHURIC ACID." A communication
from abroad by Frederic Benker and Henri Lasne, both of Paris, in the Republic
of France.
In the manufacture of sulphuric acid as at present usually conducted the gases
from the chambers before being allowed to pass into the atmosphere are made to
traverse what is known as the Gay Lussac tower.
The Gay Lussac tower is a column packed with small lumps of coke, down
which concentrated sulphuric acid is kept trickling, and its function is to bring the
gases from the chambers into intimate contact with sulphuric acid of a suitable
strength, in order that such of the nitrous compounds contained in the chamber
gases as are capable of entering into chemical combination with sulphuric acid of
such strength may be absorbed thereby, in order to be afterwards liberated
therefrom for use again.
The Gay Lussac tower thus effects a very important economy in the manufacture
of sulphuric acid, but it does not absorb the whole of the nitrous compounds
contained in the gases from the chambers, because it is only that portion of the
said compounds which is in the state of nitrous acid which can be absorbed by the
sulphuric acid of the Gay Lussac tower, whereas a large proportion of the said
compounds is in the state of nitric peroxide.
The object of a former Invention, which was communicated to John Imray by
the correspondents who have communicated to me the present Invention, and for
which former Invention Letters Patent, numbered 4522, and dated the Fourth of
November 1880, have been granted, is to increase the proportion of the nitrous
compounds contained in the chamber gases which can be absorbed in the Gay
Lussac tower by mixing with the chamber gases before they enter the Gay Lussac
tower sulphurous acid gas, which shall reduce the nitric peroxide in the chamber.
gases to the state of oxidation in which it can enter into chemical combination with
sulphuric acid. The present Invention relates to an improvement upon the said
former Invention, and consists in introducing into the chamber gases the sulphurous
acid gas which, aided by vapour of water and free oxygen, is to react upon the
nitric peroxide contained in the chamber gases as aforesaid at such a point of the
passage of the chamber gases from the chambers to the Gay Lussac tower as to
permit that before reaching the Gay Lussac tower the chamber gases and the
sulphurous acid gas which has been added to them shall have mingled sufficiently
to secure that in the Gay Lussac tower the nitric peroxide of the chamber gases
shall be absorbed and retained as nitro-sulphonic acid, from which nitrous acid for
use again can afterwards be liberated by well-known means. The sulphurous acid-
gas may either be admitted into the pipe which conveys the exit gases from the
chambers into the Gay Lussac tower, being admitted thereinto at a point sufficiently
distant from the Gay Lussac tower to permit of an approach to complete mixture
before the gases reach the Gay Lussac tower, or a special small chamber may be
interposed between the present chambers and the Gay Lussac tower, both the
exit-gases from the present chambers and the sulphurous acid gas which is to react
on their nitric peroxide being made to pass through this small additional chamber
before entering the Gay Lussac tower.
The sulphurous acid to be thus introduced into the gases coming from the
vitriol chambers may be taken from the pyrites-burners or from the sulphur-
burners, as the case may be, or it may be generated in special apparatus. My

page_text: correspondents have found it most convenient, however, to take the sulphurous
acid employed under their Invention in the state of a mixture of sulphurous acid
gas and other gases from the pipe conveying sulphurous acid gas mixed with other
gases from the Glover tower to the chambers. The sulphurous acid gas or mixture
of sulphurous acid gas and other gases to be introduced into and mixed with the
gases from the chambers as aforesaid may be either forced or aspirated or other-
wise introduced by whatever means may be preferred in each particular case, but
the means employed must be such as to permit that the quantity of sulphurous
acid gas introduced into the exit-gases from the chambers may be easily regulated
at will. My correspondents prefer to draw it from the apparatus from which it is
supplied, and to inject it into the exit-gases from the vitriol chambers by means of
an injector on the same principle as the Körting injector, but made of an alloy of
antimony and lead.
When the sulphurous acid used under my correspondents' Invention is taken
from the Glover tower, there is no need to pass it through an apparatus for freeing
it from dust, as described in the Specification of the former Invention aforesaid.
It is still necessary, however, to have with it enough vapour of water for the
accomplishment of the desired reactions, and at the same time to avoid having
with it too much vapour of water. It will therefore still be necessary in most
cases to pass the sulphurous acid gas or mixture of sulphurous acid and other gases
after it leaves the injector, but before it is introduced into the gases from the
chambers, through a small coke tower down which sulphuric acid shall be kept
trickling. The strength of the sulphuric acid supplied to this tower must vary
according to the amount of moisture in the atmosphere at the time. At Paris in
summer my correspondents supply to this tower sulphuric acid of about 1.53
specific gravity, and in winter sulphuric acid of. about 1·33 specific gravity, except
very occasionally during periods of intense cold when it is not necessary to supply
any sulphuric acid to this tower at all.
In witness whereof, I, the said Walter Weldon, have hereto set my hand and
seal, this Seventh day of November, in the year of our Lord One thousand
eight hundred and eighty-one.
WALTER WELDON. (L.S.)