An Improved Process for the Preparation of Pure Nitric Acid.
Year: 1891

page_text: Date of Application, 23rd Dec., 1891
Complete Specification Left, 10th Aug., 1892-Accepted, 17th Sept., 1892
PROVISIONAL SPECIFICATION.
An Improved Process for the Preparation of Pure Nitric Acid.
A communication to me from OSCAR GUTTMANN and LUDWIG ROHRMANN, of
Krauschwitz, near Muskau, in the Empire of Germany.
I, EDMUND EDWARDS, of the firm of Edwards and Co., Patent Agents and
Engineers, of 35, Southampton Buildings, Chancery Lane, in the County of
Middlesex, do hereby declare the nature of this invention to be as follows:-
As is well known, nitric acid prepared in the usual way, by distillation, contains
according to the yield of chlorine of the nitrate of soda used, and the degree of heat,
a varying proportion of nitrous acid, which, particularly in the case of the manu-
facture of nitric acid from acid waste of nitrous materials, is considerable, and
which heretofore has been removed from the finally condensed acid, by means of a
special process.
This process is effected either by heating the acid and introducing
a stream of cold or hot air, or by blowing air into the vessel immediately after the
condensation of the acid, or in various other ways, but always by the treatment of
the finished acid, the nitrous acid being only slowly removed, and often remaining
in some other form.
By the improved process which forms the subject of the present invention on the
other hand the acid in a gaseous condition is treated at the very moment of its
formation so that not only an intimate action of the air and acid upon one another
are obtained, but also the nitrous acid by the action of the air and of the water
contained in the acid, is at once converted to nitric acid, so that pure nitric acid
results.
This removal of water has the further advantage that the nitric acid left is
highly concentrated.
The process consists in the introduction of an air blast between the distillation
and the condensing apparatus so that the acid in a gaseous form becomes mixed
with 'air, on its way from the distilling to the condensing apparatus, before it has
had time to condense. By the use of an air blast in this way, not only does the
air in the gaseous acid assist the passage of the latter to the condensing apparatus,
and carry the halogen combinations which arose from the condensing apparatus to
the towers or other apparatus for the interception of the last traces of gas but it
also causes a partial vacuum in the distilling vessel, so that the distillation is
accelerated and can be conducted at a lower temperature.
The blast of air can be produced in any convenient way, and may be used either
cold, or preferably hot, for which purpose it may be passed through a coil of pipes
in the flue of the furnace.
Thated this 22nd day of December 1891

page_text: A communication to me from OSCAR GUTTMANN and LUDWIG ROHRMANN, of
Krauschwitz, near Muskau, in the Empire of Germany.
I, EDMUND EDWARDS, of the firm of Edwards and Co., Patent Agents and
Engineers, of 35, Southampton Buildings, Chancery Lane, in the County of
Middlesex, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement and accompanying drawing, that is to say :-
As is well known, nitric acid prepared in the usual way, by distillation, contains,
according to the amount of chlorine in the nitrate of soda used and the degree of
heating, a varying proportion of low oxides of nitrogen such as nitrous acid, which,
particularly in the case. of nitric acid manufactured from the waste acids of nitro-
compounds, is considerable, and which hitherto has been removed from the finished
acid. This removal is effected either by warming the acid and introducing a
current of cold or hot air, or in various other ways, but always by treatment of the
finished acid, the low oxides being only slowly removed or sometimes recovered in
some other form.
By the improved process which forms the subject of this invention on the
contrary the acid is treated in a gaseous state at the very moment of its formation,
whereby not only an intimate reaction upon each other of air and acid is obtained,
but also the low oxides are immediately converted into nitric acid by the action of
the air and the water contained in the acid, so that pure nitric acid results. This
abstraction of water has the further advantage that the nitric acid is more con-
centrated than usual.
In order that the present invention may be more fully understood, reference is
made to the accompanying sheet of drawing.
The improved process consists in producing gaseous nitric acid in the distilling
vessel A by distilling nitre or saltpetre with sulphuric acid. The gaseous nitric
acid thus produced is passed from the vessel A through a conduit of pipes B to a
condenser C consisting of an inclined main pipe a and a quantity of vertical pipes b
communicating with the said main pipe. The main pipe a is divided by walls or
plates c into several chambers, which are connected with one another by means of
small elbow joints d.
Every chamber of the main pipe a communicates with two vertical pipes b.
These pipes are connected with the adjacent pipes b of the adjoining chambers by
means of bent tubes e.
b
It is obvious that the gases in consequence of the above explained arrange-
ment will pass from one pipe b to the next one whereby a condensation is
effected. The condensing liquid is collected in the chambers of the main pipe a
and passing from the higher situated chamber to the lower ones it enters finally
the reservoir D. The elbow joints d being filled up with condensing liquid
prevent the escape of the gases to the reservoir D thereby causing the gases to
pass along the pipes or coils of the condenser C.
Before the gases produced in the distilling vessel A enter the condenser an
air blast is introduced in the conduit B by means of an injector or other suitable
apparatus, which mixes the gaseous acid with air on its way from the distilling
vessel A to the condenser C.
I prefer to arrange the injector in the manner shewn in Figure 2, where it will
be seen that it consists of a hollow mouthpiece E to be inserted in the conduit B.
Through the said mouth piece E air is blown into the conduit B so that the
gaseous acid immediately after its formation is mixed with air, thereby obtaining
the above mentioned advantages. By thus using an air blast the air current

page_text: introduced into the gaseous acid carries along the halogen combinations from the
condenser C to a vessel jointed with the condenser and adapted to collect the last
residues or remains of gas, and also causes a partial vacuum in the distilling
vessel A. so that the distillation is accelerated and effected at a lower temperature.
The air blast may be produced in any convenient way and be used either cold
or preferably hot, for which purpose the conduit or pipe F is heated in a suitable
manner.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The process which consists in introducing an air blast into the gascous nitric
acid immediately after its formation and before its condensation, for the purpose of
converting the low nitric oxides into nitric acid of high concentration.
2. The arrangement of an air blast E in the conduit B between the distilling
vessel A. and the condenser C for the purpose of mixing the gaseous acid with air,
of carrying away from the condenser the halogen combinations formed, and of
causing a partial vacuum in the distilling vessel, substantially as described with
reference to the drawing.
Dated this 10th day of August 1892.
EDWARDS & Co.,
35, Southampton Buildings, London, Agents for the Applicant.