Process for Purifying Cruie Acetic Acid.
Year: 1896

page_text: Pate of Application, 9th Nov., 1896-Accepted, 16th Jan., 1897
COMPLETE SPECIFICATION.
Process for Purifying Cruie Acetic Acid.
I, ADOLF SCHMIDT, of 49 Kölnische Strasse, Cassel, in the German Empire,
Director of the Actiengessellschaft für Treber Trocknung do hereby declare the
nature of this invention and in what manner the same is to be perfor.nel, to be
particularly described and ascertained in and by the following statement, that is.
to say :-
Heretofore, chemicals giving off oxygen have been chiefly employed for oxidising
and rendering harmless the empyreumatic constituents of crude acetic acid, e.g. tar,
sulphurous acid. Such a process, however, is expensive and leads to consilerible
loss of acetic acid.
The process which forms the subject of the present invention consists in obviating
the above mentioned defect by effecting the oxidation of the crude acetic acid by
nieans of commercial pure oxygen in suitable apparatus.
In this process it is important to keep the crude vegetable acid, warmed, aul
under pressure, in intimate mixture with the oxygen until the acetic acid has.
become completely purified.
For this purpose, I employ a high strong-walled charcoal filter, which can be
heated by any suitable means, having its inside lined with acid resisting material,.
and provided with the necessary pressure regulating apparatus (safety valve,
pressure gauge, &c.). The upper flour of the filter is connected with a force pump,
by means of which the crude acetic acid is pumped in; at the bottom, the filter is
connected with a steel flask or cylinder filled with oxygen, and is further provided
with an outlet pipe, bent into a deep U shape to correspond with the pressure in
the apparatus. The filter is filled, in appropriate manner, with small pieces of
charcoal, or coke, about the size of nuts, and then closed. By suitably opening
the reducing valve, a weak stream of oxygen is introduced into the apparatus, and
then, by means of a force pump, the acetic acid to be treated, is pumped, in a fine
jet, into the filter. The acetic acid, which is finely divided by means of the layers.
in the filter remains in its entire course through the filter in the closest contact
with the oxygen which oxidises the tarry constituents into insoluble resinous matter
which is retained in the layers of the filter, and, on the other hand, oxidises into
sulphuric acid, any sulphurous acid that may be present (resulting from the treat-
ment of acetate of lime or soda with sulphuric acid). The acetic acid purified or
containing only sulphuric acid, flows off through the outlet tube, at the bottom of
the filter, and is freed from the sulphuric acid by distillation over a suitable
quantity of pure acetate of sodium.
A form of apparatus suitable for carrying out the herein described process is
shown in the accompanying drawings.
A is the charcoal filter, and B is a rose or spraying nozzle in connection with
the inlet pipe R through which the crude acetic acid delivered by the force
pump 1, is introduced into the upper part, of the apparatus above the perforated
plate T. This plate serves to still further divide the acid before it enters the
filtering column of charcoal. Near the lower part of the filter A, there is also a
perforated plate T¹ to support the filtering column of charcoal, and to split up the
oxygen sprayed through a rose B connected to the end of the pipe R' leading
from the steel flask or cylinder O containing compressed oxygen for the purpose of
oxidizing the acetic acid as herein before stated. The acid is drawn off, through.
the U-shaped nine L. into a suitable receiver.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same may "be performed, I declare that what I
claim is:-
1. The process for the purification of vegetable acetic acid from its empyreumatic
constituents, consisting in pumping in the acetic acid from above, in a fine jet, into
a closed filter filled with charcoal, or coke, while, at the same time, a weak stream
of pure oxygen under pressure is directed into the apparatus for the purpose of
intimately mixing with the acetic acid; and for oxidising the tarry constituents into
insoluble resinous matter which remains clinging to the filtering material,
substantially as set forth.
2. The application of the above claimed process to acetic acid obtained by
treating acetate of lime with sulphuric acid, and the subsequent distillation of the
same over pure acetate of sodium for removing the sulphuric acid resulting from
the oxidation of the sulphurous acid in the filter, substantially as described.
Dated this 9th day of November 1896.
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 54 Market Street, Nottingham,
Agent for the Applicant.