A Process of and Apparatus for Distilling and Condensing Nitrio Acid, Tar, and other Liquids.
Year: 1894

page_text: Date of Application, 28th July, 1894-Accepted, 26th Jan., 1895
COMPLETE SPECIFICATION.
A Process of and Apparatus for Distilling and Condensing Nitrio
Acid, Tar, and other Liquids.
I, WILLIAM BESTWICK MAXFIELD of No. 19 Bowling Green Street, Leicester
in the County of Leicester, England Registered Patent Agent do hereby declare
the nature of this invention as communicated to me by Wilhelm Dieterle of
Feuerbach near Stuttgart, Doctor, and Ludwig Rohrmann of Krauschwitz near
Muskau, Province of Silesia, Germany, Manufacturer 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 a process of and apparatus for distilling and condensing
nitric acid, tar and other liquids, or the production of nitric acid free from halogens
and from nitro-sulphuric acid.
In the patented processes having for their object the production of pure or
purified nitric acid from ordinary nitre rendered impure by halogenous salts,
constant use has been made of the law on the displacement of gases from liquid
solutions by forcing in an excess of air, or of another inert gas, and this law was
applied to distilling or for acid already distilled.
It is to be understood therefore that in this process the impure nitric acid is
distilled the gaseous impurities accompanying the nitric acid during the whole
process of distillation-so that the purifying agent must be of constant strength
from the beginning to the end of the distilling process whereby the preparation of
a chemically pure acid is rendered very difficult.
In carrying out our improved process we start from the fact that there exists in
the vessel wherein the reaction takes place and immediately after the mixing of
saltpetre with sulphuric acid, in suitable proportions, ready formed nitric acid in the
highest degree of concentration as the water added with the nitre and the sulphuric
acid are combined with the acid sulphate at the temperature hereinafter mentioned.
The result thereof is that a comparatively low temperature from 50° to 60° C.
or thereabouts, all the halogenous hydracides proceeding from the nitre become
oxidized and are converted into free halogens while a corresponding mass of nitric
acid is reduced to a lower order of nitrogenous oxides. Should air or another
inert gas be blown into the vessel from the beginning and throughout the heating
of the treated mass, all gaseous impurities chiefly halogens and nitrogenous oxides
of the lower orders are removed from the nitric acid before the distillation that is
This great
to say, that purified instead of impare nitric acid being distilled.
advantage is particularly noticeable when using nitre sullied by a large quantity
of chloride of sodium, as in this case the above process allows of pure nitric acid
free of halogens and nitro-sulphuric acid being produced which could not or only
be imperfectly obtained by the other usual processes. It is a well known fact that
during the distillation proper, either through over heating or through the action
of the nitric acid upon the material of the vessel a small evolution of reduced
gaseous products from the nitric acid takes place. To prevent these gaseous
products from being absorbed by the distilled acid and rendering the latter impure, a
current of air or of another inert gas is conveyed throughout the distillation into
the contents of the vessel; as according to the same law, that is to say, the law
of the displacement of gases from their solution by another gas the latter being
introduced in large excess, it follows that the absorption or solution of such gas by
a liquid in the presence of another inert gas which is in excess of it, must obviously
be prevented.

page_text: To carry into practice the steps above set forth, the cooling apparatus shown
in cross section Figure 1 is made use of, Figure 2 being a plan of the same.
Figure 3 is a cross section of a modification of my invention and Figure 4 a plan
thereof.
Similar letters of reference indicate similar parts throughout the drawings.
A
A in these drawings represents the generating receptacle containing the mixture
into which air or other indifferent gas is forced by means of a tube "B." From this
receptacle the air laden with vaprous nitric acid is conducted by a pipe "d" to the
cooler or condenser composed of a series of coils of pipe forming a worm.
tube b is connected to the coils of the worm by small or branch inclined pipes
and terminates in a suitable reservoir, provided with a siphon cock as shown at "h."
The lower coil of the cooler or condenser communicates through a suitable pipe
with the receiver "K" for the purified nitric acid.
66
a,
"
The air laden with the nitric acid, and the impurities pass to the cooler and
condensation thereof takes place in the upper coils, and in order that this
condensation may more tranquilly and effectually take place, the said upper coils
(three in the drawing) are not in communication with the tube or canal "b." By
this means a nitric acid free of balogen and nitrous acid is produced within the
cooler, and in this quality the nitric acid is then conveyed to the receiver K.
As the most concentrated nitric acid possesses at an ordinary temperature, a
considerable tension, it unavoidably occurs at the beginning of the introduction of
air into the contents of the vessel wherein the reaction takes place, before the
removal of chlorine and the bleaching have taken place. The bleaching has for
its object, to discolour colcured artificial or natural products and to obtain products
which are more or less white or pale, small quantities of nitric acid are carried
away in the cooler showing still a slight colour and having a slight chlorine
reaction. In order to collect this first production a branch pipe is inserted
between the cooler and the receiver K and is provided with ground syphon
valves "f" and "g" the first of which serves to receive and remove the first
portion of acid produced, after which the valve "g" is opened, when the ordinary
distillation can proceed.
€5
The separated air first produced is put back in the still and serves again for the
purposes of purification. Furthermore it is impossible to prevent during the whole
course of the distillation, small volumes of nitric acid vapours from being carried.
away with the air through the pipes a, a," and thence into the gas outlet "b";
wherein they are condensed. To collect this acid 1 use the reservoir aforesaid
placed at the lower end of the outlet "6" and provided at the bottom with a
syphon valve "h." This reservoir is formed in the manner shown the outlet "b"
extending for a given length under the small pipes "a." By means of the valve "h"
either the acid is allowed to drip continuously from the larger pipe and is collected
separately or the valve being closed the acid is allowed to pass through the
lowermost pipe "a" of the last coil "Y" of the cooler into the receiver K and is
added to the other distillate.
.
Both syphon valves "f and "allow tests being made at any time during the
course of distillation.
The acid condensed in the canal "6" is obviously stronger than that condensed
in the cooler. The outlet has a larger diameter than the cooling pipe and can be
extended upwards and connected to an absorption apparatus.
The cooler thus described may be likewise made of glass or metal and is suitable
for all kinds of distillation in which corroding gases are produced such as for
instance in the distillation of tar and the like.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :--
1. A process for the production of nitric acid free of halogens and nitro-sulphuric
nowind and

page_text: free nitric acid, and by separating and leading away the air containing the impure
gases from the nitric acid condensed in the cooler.
a, a," with &
2. For the purpose of carrying this process into practice a cooling apparatus
the cooling coils of which are connected by the ascending pipes
perpendicular outlet channel or pipe "6" leading at its lower end to a reservoir
provided with a syphon valve "h for the purpose of removing the air blown
directly into the mixture in the vessel and carrying away the impurities with it,
substantially as and for the purpose set forth.
"
Dated this 25th day of July 1894.
WILLIAM BESTWICK MAXFIELD,
19, Bowling Green Street, Leicester, England,
Registered Patent Agent.