Process for the Separation and Purification of Nitrate of Ammonia.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Process for the Separation and Purification of Nitrate of Ammonia.
ROBERT NICOL LENNOX, Rosebank Works, Fulham, London, S.W., Chemist, do
hereby declare the nature of this invention to be as follows:-
-
Sulphate of ammonia is intimately mixed with. the nitrate of a metal capable
of double decomposition, and put into a closed retort, which, during the operation
is exhausted to as low a pressure as possible, it is then slowly heated to such a
temperature that the nitrate of ammonia formed distils off and is condensed in a
suitable condenser. As an example, 17 parts of nitrate of soda, are mixed with
13 parts of sulphate of ammonia, and are distilled in vacuuo until the whole of the
nitrate of ammonia has passed into the condenser. The nitrate of ammonia may
again be distilled in vacuuo, as often as necessary for its complete purification.
It is well known that double decomposition between, say, nitrate of soda and sul-
phate of ammonia, takes place.
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COMPLETE SPECIFICATION.
Process for the Separation and Purification of Nitrate of Ammonia.
I, ROBERT NICOL LENNOX, of Rosebank Works, Fulham, in the County of London,
Chemist, do hereby declare the nature of this invention, and in what
manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
This invention consists in manufacturing and purifying nitrate of ammonia by
a process involving the distillation of the salt in vacuo, or under diminished pressure
that is to say a pressure less than that of the atmosphere. According to this-inven-
tion I take sulphate of ammonia and mix it intimately with the nitrate of a metal,
capable of double decomposition, such, for example, as nitrate of soda. The salts
are dried, or used in their ordinary commercial condition, and in, or about, molecular
proportions, namely seventeen parts by weight of nitrate of soda to thirteen parts
by weight of sulphate of ammonia, a slight excess of either salt over the molecular
proportions being preferable owing to the fact that the dissociation of the ammonia
salts is thereby diminished. The mixture of the salts is placed in a closed vessel,
or retort, the interior of which is placed in connection with a pump, or exhauster,
by which the pressure inside the said vessel, or retort, (and also in the condenser
scrubber and connecting pipes hereinafter mentioned) is reduced to as low a degree
DO71

page_text: as convenient and heat is then applied to the vessel, or retort, so that the contents
are slowly heated to such a temperature that the nitrate of ammonia formed distils
off, it being condensed in a condenser which leads into a scrubber with which the
pump, or exhauster, is connected. In carrying out the process, after the vessel,
or retort, is charged with the mixture of the said salts, the whole interior of the
apparatus is put under vacuo, or has the pressure reduced to below that of the
atmosphere and heat is applied to the vessel, or retort, care being taken that
the contents thereof during the process of distillation are not heated to above
230° Centigrade, and that the upper part of the vessel or retort which is filled with
gaseous nitrate of ammonia, and its products of dissociation and partial decomposi-
tion, is not superheated. At about 200° Centigrade the nitrate of ammonia distils
off leaving the non-volatile sulphate of soda in the vessel, or retort, and the said
nitrate of ammonia is condensed in the condenser which is made of earthenware
pipes, or other suitable material, which will not be injured by the products. The
vessel, or retort, may be made of iron, or other material which will not be acted
upon injuriously by the contents thereof and will not damage the product. I find
that the best results are obtained by working at as low a pressure, (or as high a
vacuum), as can be conveniently maintained in practice, say, for example, a
pressure equal to one inch of mercury, but a pressure even up to say about six inches
of mercury may be employed without the destruction of a very material amount
of the nitrate of ammonia. Any nitrous oxide produced during the process may
be collected from the discharge from the pump, or exhauster, and be condensed
into the liquid state.
Several vessels, or retorts, may with advantage be used all distilling into the same
condenser, so that one, or more, of such vessels, or retorts, may, at different stages
of the heating always be in operation.
A slight leak of air, ammonia, or other gas which does not act detrimentally
on the substances undergoing reaction, may be allowed to enter the vessel, or retort,
or vessels, or retorts, during the distillation, provided the exhaustion be well main-
tained in spite of the leak.
The scrubber is charged with a strong solution of nitrate of ammonia, or other
material capable of absorbing any nitric acid, and ammonia which may result
from dissociation of nitrate of ammonia so that vapours of neither nitric acid or
ammonia reach the pump, or exhauster.
In order to remove the solid nitrate of ammonia from the condenser and to
prevent obstruction in the pipes thereof a jet of steam may be introduced into the
condenser during the condensation.
The nitrate of ammonia may be completely purified by again distilling it in
vacuo, or under a pressure lower than that of the atmosphere, and under conditions
as to temperature as hereinbefore described.
I am aware that the volatilization or sublimation of nitrate of ammonia at atmo-
spheric pressure is known, but this results in the destruction of such a large
amount of the nitrate that it is not commercially available, and I am also aware
that the double decomposition of a mixture of sulphate of ammonia and nitrate
of soda is known, and I therefore do not claim these as novel.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The separation of nitrate of ammonia from a mixture of sulphate of ammonia
and nitrate of soda, or nitrate of other metal, by distillation in vacuo, or under a
pressure less than that of the atmosphere at such a temperature that material
destruction of the nitrate of ammonia does not occur; substantially as hereinbefore
described.
2. The purification of nitrate of ammonia from non-volatile substances by distil-
lation in vacuo, or under a pressure less than that of the atmosphere and under
conditions of heating; substantially as hereinbefore described.

page_text: 3. The manufacture of nitrate of ammonia by the process conducted substantially
s hereinbefore described.
Dated this 3rd day of November 1897.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.