IMPROVEMENTS IN THE SEPARATION OF VAPOURS OR VOLATILE BODIES FROM GASES OR OTHER VAPOURS WITH WHICH THEY MAY BE ADMIXED
Year: 1878

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
the Invention of "IMPROVEMENTS IN THE SEPARATION OF VAPOURS OR
VOLATILE BODIES FROM GASES OR OTHER VAPOURS WITH WHICH THEY MAY BE
ADMIXED." A communication from abroad by Theophile Schloesing, of Paris,
Professor of Chemistry.
Sealed the 19th July 1878, and dated the 15th February 1878.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 15th February 1878.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
SEPARATION OF VAPOURS OR VOLATILE BODIES FROM GASES OR OTHER VAPOURS
WITH WHICH THEY MAY BE ADMIXED." [A communication from abroad by Theophile
Schloesing, of Paris, Professor of Chemistry.]
Up to the present time the processes employed for the separation of volatile
bodies from gases in chemical operations have always been based on the principle
of cooling. This method, which is usefully applicable to easily condensible bodies,
is without effect when any obstacle arising from their nature or from the mixture
in which they are found opposes their condensation by the influence of cold alone.
In is this case it has been sought to absorb them by bringing them into contact with
substances capable of forming with them combinations of a more or less fixed
nature, but only a partial result is thus obtained, and only by the employment of
large apparatus arranged to present extensive contact surfaces.
::
It appears not to have been perceived hitherto that cooling has, upon the bodies
which are thus brought into a state of suspension in the medium from which they
have to be separated, the effect of depriving them of their gaseous tension, con-
sequently leaving nothing to carry them into contact with the absorbing surfaces
but the mechanical current in the prolonged course along which they are com-
pelled to flow, whilst on the other hand in the state of gaseous tension the absorption
D

page_text: The adsorption or Que vapours of nitric acid Can
similar to those which have been described for the absorption of hydrochloric
acid.
AMMONIACAL GAS.
Ammoniacal gas, when it is wholly uncombined, but contained in a gaseous
mixture, possesses gaseous tension at the ordinary temperature. It can then be
absorbed by water or by acid without having recourse to elevation of the tempe-
rature; but in manufactures where ammoniacal gas is produced or employed this

page_text: body is frequently dissemminated in gaseous natters, amongst which it meets with
such as are capable of entering into combination with it, and this combination
may not have tension, or may have too small a tension at the temperature of the
gaseous mixture, so that it exists at least in part in the state of a liquid or solid
dust able to traverse with impunity the apparatus intended to absorb it.
The application of my principle of putting volatile bodies into tension is in the
case mentioned above and in analogous cases very simple. It is only necessary to
raise the gaseous mixture to a suitable temperature to bring the ammoniacal com-
binations into a state of tension, and in the case of carbonate of ammonia, a tempe-
rature of 120 to 130 is sufficient; whether there be at this temperature dissociation
between the acid and the alkali, or whether the combination be permanent, is
unimportant.
The mixture is introduced into the lower part of a tower filled with coke watered
with dilute sulphuric acid, and maintained throughout at a temperature suitable to
preserve the state of ammoniacal tension.
In certain cases in the treatment of wash waters, gas water, and the like, the
ammonia is found from the nature of the manufacture in the state of gaseous
tension in admixture with vapour of water. It is customary to condense this
mixture of vapours, which yields liquid ammonia. This method expends uselessly
a large quantity of heat. The new principle finds here its application in suppressing
the condensation and effecting the absorption of the ammonia by a dilute acid
flowing down a tower charged with coke, whilst the steam freed from ammonia is
employed to heat distilling apparatus.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sydney Pitt in the Great Seal Patent Office on the 14th
August 1878.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
SEPARATION OF VAPOURS OR VOLATILE BODIES FROM GASES OR OTHER VAPOURS
WITH WHICH THEY MAY BE ADMIXED." (A communication from abroad by Theophile
Schloesing, of Paris, Professor of Chemistry.)
Up to the present time the processes employed for the separation of volatile
bodies from gases in chemical operations have always been based on the principle
of cooling. This method, which is usefully applicable to easily condensible bodies,
is without effect when any obstacle arising from their nature or from the mixture
in which they are found opposes their condensation by the influence of cold alone.
In this case it has been sought to absorb them by bringing them into contact with
substances capable of forming with them combinations of a more or less fixed
nature, but only a partial result is thus obtained, and only by the employment of
large apparatus arranged to present extensive contact surfaces.
It appears not to have been perceived hitherto that cooling has, upon the bodies
which are thus brought into a state of suspension in the medium from which they
have to be separated, the effect of depriving them of their gaseous tension, con-
sequently leaving nothing to carry them into contact with the absorbing surfaces
but the mechanical current in the prolonged course along which they are compelled
to flow, whilst on the other hand, in the state of gaseous tension, the absorption
itself sets up a continual flow of the volatile body towards the absorbing surface,
and absorption takes place actively without requiring the same extension of the
contact surfaces.
My Invention then consists in preserving or producing, according to the nature
of the body in all operations of this sort, a. temperature such as to maintain the
body to be absorbed in a state of gaseous tension during the operation of absorption,
which has the effect of rendering the absorption rapid and complete, and permits
of a considerable simplification of the apparatus employed.
The preceding explanation will suffice to enable a competent person to follow
the course of the different applications which may be made of my Invention.
However, without limiting its scope, I will proceed to describe some of the more
important applications in manufacturing chemistry. I will refer in succession to
the absorption of hydrochloric, sulphuric, and nitric acids, and of ammonia.
HYDROCHLORIC ACID.
I retain the general arrangements now in use for the condensation of hydro-
chloric acid gas, except that I introduce two essential modifications in the use of
condensing towers; at the outset I much reduce.the dimensions of these apparatuses.
I calculate their capacity on the basis of 150 to 200 litres for each 100 kilos. of
salt decomposed in 24 hours; and further, I do not introduce the gaseous mixture
containing the hydrochloric acid gas until it has been brought to a temperature
very much higher than 100°. Then the first effect of the gases entering the
tower is to evaporate a part of the descending liquids. This reduces their tempe-
rature nearly to the boiling point of these liquids; then they carry with them the
vapour produced throughout their whole course, so that the interior of the tower is
raised throughout to a temperature of 100° at the least. On the other hand,
the supply of water to the summit of the tower can always be regulated, so that
an excess of water remaining unevaporated flows constantly down the tower;
although this water is heated to 100° nearly, it still retains its property of absorbing
hydrochloric acid gas. Indeed, it is capable of absorbing it to the point of forming
the stable hydrate boiling at 108°, and containing 18.5 per cent. of real acid. There
are thus in the tower two currents passing in opposite directions, one of gas and

page_text: rature; but in manufactures where ammoniacal gas is produced or employed this
body is frequently dissemminated in gaseous matters, amongst which it meets with
such as are capable of entering into combination with it; and this combination
may not have tension, or may have too small a tension at the temperature of the
gaseous mixture, so that it exists at least in part in the state of a liquid or solid
dust able to traverse with impunity the apparatus intended to absorb it. It is so
in particular in manufactories where common salt is converted into carbonate of
soda by means of carbonate of ammonia.
Whatever process may be adopted one has always to deal with a gaseous mixture
containing ammonia which has escaped absorption by pure or salt water and
carbonic acid. In this mixture there is then carbonate of ammonia in the state of
suspended dust, a dust which is always more or less drawn forward by the gases
out of the apparatus intended to absorb the ammonia. This is the principle cause
of the loss of ammonia to which the manufacturer is exposed.
The application of my Invention is in the case mentioned above and in analogous
cases very simple. It is only necessary to raise the gaseous mixture to a suitable
temperature to bring the ammoniacal combinations into a state of tension, and in
the case of carbonate of ammonia a temperature of 120 to 130 is sufficient. Whether
there be at this temperature dissociation between the acid and the alkali, or
whether the combination be permanent is unimportant.
The mixture is introduced into the lower part of a tower filled with coke watered
with dilute sulphuric acid, and maintained throughout at a temperature suitable to
preserve the state of ammoniacal tension.
When one has recourse to heat to determine the absorption of the alkali one is
astonished at the rapidity of the absorption, and at the smallness of the space
necessary to realise it completely.
In certain cases in the treatment of wash waters, gas water, and the like, the
ammonia is found from the nature of the manufacture in the state of gaseous
tension in admixture with vapour of water. It is customary to condense this
'mixture of vapours which yields liquid ammonia. This method expends uselessly
a large quantity of heat. The Invention finds here its application in suppressing
the condensation and effecting the absorption of the ammonia by a dilute acid
flowing down a tower charged with coke, whilst the steam freed from ammonia
is employed to heat distilling apparatus.
I would have it understood that the Invention is not limited to the apparatus
herein described, which will be varied to suit the special operation in which it is
employed, but I claim as the Invention,-
The treatment of volatile bodies under the conditions already defined in such
manner as to maintain them in a state of gaseous tension, and so to determine a
rapid absorption.
I also claim the separation of the vapours of hydrochloric acid, of sulphuric acid,
of nitric acid, and of ammonia from gases or other vapours with which they may
be admixed, substantially by the means herein described.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Tenth day of August, in the year of our Lord One
thousand eight hundred and seventy-eight.
SUTNY
SYDNEY FITT. (LS.)