Improvements in the Treatment of Cotton Cloths for Filtering Purposes.
Year: 1893

page_text: Date of Application, 26th Jan., 1893
Complete Specification Left, 23rd Oct., 1893-Accepted, 25th Nov.,
1893
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Mr. E. DE HAEN, of List vor Hanover, in the
Empire of Germany.]
Improvements in the Treatment of Cotton Cloths for Filtering
Purposes.
I HENRY EDWARD NEWTON of The Office for Patents, 6 Breams Buildings,
Chancery Lane in the County of London, Patent Agent, do hereby declare the
nature of this invention to be as follows:-
The cotton pressing cloths employed for filtering acid liquids in filter presses,
rapidly become destroyed, and consequently useless. It is also a fact, that nitrated
cellulose has a greater power of resistance to the action of acids than cellulose
itself.
In order to obtain a filtering material which will resist acids, my foreign corre-
spondent has tried to nitrate the cotton material by means of the processes usually
employed. It is a matter of high importance, that the cotton cloth thus treated
should retain its strength and permeability for liquids.
My foreign correspondent has now found that a cotton material answering all
demands for filtering purposes results, if the process of nitration is modified in a
certain manner, viz., by placing the material or cloth in cold nitric acid, at from
40 to 50 degrees Baumé, for about one hour, and after the adherent nitric acid has
been allowed to drain, by subsequently placing the material or cloth for some time
in concentrated sulphuric acid at about 66 degrees Baumé, and finally washing
with water, until the washings no more show an acid reaction.
The fibrous material thus treated, withstands the action of all acids, even
concentrated hydrochloric acid, in which cellulose easily dissolves.
According to the researches of my foreign correspondent, the following chemical
process takes place :-In placing the material in nitric acid, an impregnation merely,
is effected, whilst the true nitration proceeds only on placing the material in
sulphuric acid.
Obviously, the result thus obtained is of high technical value.
"
The cotton cloth loses by such or similar treatment, neither its strength nor its
permeability, in which respect it equals the material not nitrated. It resists the
action of acids, and, in consequence, is at least four times as durable, is capable of
being more widely employed for filtering purposes than ordinary cotton material;
and it is considerably cheaper and even more durable than woollen material which
is sometimes used.
The extensive employment and the advantages resulting from the use of cotton
material nitrated in the above or a similar manner, have been distinctly, proved by
my foreign correspondents by a great number of experiments in practice.
Of course, my foreign correspondent does not limit himself to the method of
nitrating above referred to. The proportions above given can be varied. Such
modifications do not alter the nature of this invention, which relates to the production
of a cotton material which will resist acids, and be capable of being employed for
filtering purposes, by means of a suitable treatment of ordinary cotton material
with nitric acid and sulphuric acid, or with other substances producing the like or
a similar effect.
The method of nitrating hereinbefore explained, yields not only the said results,
but further possesses the advantage, that, by employing separately the two acids,
the resulting waste acids can again be used, as such, for other purposes.
Detalii et d of Leve1802
I
}
NEWTON & SON,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Treatment of Cotton Cloths for Filtering
Purposes.
I, HENRY EDWARD NEWTON of the Office for Patents, 6 Bream's Buildings,
Chancery Lane, in the County of London, Patent Agent, 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 :-
The cotton pressing cloths employed for filtering acid liquids in filter presses
rapidly become destroyed, and consequently useless.
It is true, that woollen filtering cloths resist in a higher degree the action of
acids, but they are not so cheap as cotton filtering cloths.
It is also a fact that nitrated cellulose has a greater power of resisting the action
of acids than sellulose itself.
In order to obtain a filtering material which will resist acids, my foreign corre-
spondent has tried to nitrate the cotton material by the usual processes. It was a
matter of high importance that the cotton cloth thus treated should retain its
strength and remain permeable by liquids. These researches have, however, shewn,
that a nitrated cotton cloth which possesses the required permeability and mechanical
strength, and which will withstand the action of acids to the necessary extent,
could not be obtained in this way, though the mode of working, and the quantities
of the nitrating agents (viz., sulphuric acid and nitric acid or nitrates), have been
varied in many respects.
My foreign correspondent has, however, found that a cotton material answering
all demands for filtering purposes may be prepared by modifying the process of
nitration in a certain manner, viz., by immersing the material or cloth in cold nitric
acid at from 40 to 50 degrees Baumé during about an hour, and after the adherent
nitric acid has been allowed to drain away, then subsequently immersing it during
an hour in concentrated sulphuric acid at about 66 degrees Baumé, after which
treatment it is washed with water until the washings no longer shew an acid
action.
The fibrous material thus treated, withstands the action of all acids, even
concentrated bydrochloric acid, in which cellulose easily dissolves, and my foreign
correspondent has ascertained by experiments that cotton material treated in the
manner hereinbefore described, or in a similar way, is at least four times as durable
as the unnitrated material.
According to the researches of my foreign correspondent, when the material is
immersed in nitric acid, it becomes, for the most part, merely impregnated with
the acid, nitration only taking place on subsequently immersing the material in
sulphuric acid.
Obviously the result thus obtained is of high technical value.
By such or similar treatment, the cotton cloth loses neither its strength nor its
permeability, in which respects it equals the unnitrated material. It resists the
action of acids, and is not only at least four times as durable as, but is also capable
of being more widely employed for filtering purposes than, ordinary cotton material,
and it is considerably cheaper, and even more durable than the woollen material
which is sometimes used.
The extensive employment and the advantages resulting from the use of cotton
material nitrated in the above or a similar manner, have been distinctly proved by
my foreign correspondent by a great number of practical trials.
As a matter of course, my foreign correspondent does not limit himself to the
method of nitrating above referred to. The proportions above given can be varied.
The strength of the sulphuric acid employed may vary from 62 to 68 degrees Baumé.
Such modifications do not alter the nature of this invention, which relates to the
production of a cotton material which will resist acids, and which can be used for
filtering purposes by means of a suitable treatment of ordinary cotton material

page_text: with nitric acid and sulphuric acid, or with other substances producing the like or
a similar effect.
The method of nitrating hereinbefore explained, not only yields the said results,
but possesses the further advantage that, by using the two acids separately, the
resulting waste acids can again be used as such for other purposes.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed (as communicated
to me from abroad), I declare that what I claim is :-
1. The process of producing cotton material suitable for filtering purposes,
capable of resisting the action of acids, while retaining its original strength and
permeability, which process consists in treating ordinary cotton material, first with
cold nitric acid (at from 40 to 50 degrees Baumé), and subsequently with con-
centrated sulphuric acid (at from about 62 to 68 degrees Baumé).
2. The cotton material treated in the manner hereinbefore defined, or in any
other way affording the same result.
3. The employment of the cotton material prepared in the manner hereinbefore
defined, or in any other way affording the same result, for filtering purposes.
Dated this 4th day of October 1893.
NEWTON & SON,
Agents for the Applicant.