Process for Manufacture of Acetic Acid.
Year: 1892

page_text: COMPLETE SPECIFICATION.
A Process for Manufacture of Acetic Acid.
We, ERMENEGILDO ROTONDI, of 32 Via Ospedale, Turin, Italy, Professor of
Chemistry at the Industrial Museum of Turin, and Chevalier MARIO MICHELA,
of 32 Via Vittorio Emanuele, Florence, Italy, Gentleman, 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 object of our invention is to decompose pyrolignites or acetates by
bisulphate of soda and then to distil acetic acid by operating as we shall describe.
Pyrolignites or acetates, pulverised or in the state of very concentrated solution,
are treated with such a quantity of bisulphate of soda also in powder or in the
state of very concentrated solution as to bring together about two equivalents
of bisulphate of soda to each equivalent of pyrolignite or acetate.
It will generally be found sufficient to mix with each equivalent of pyrolignite or
acetate two and a quarter equivalents of bisulphate of soda such as it is obtained as
a residuum in the manufacture of nitric acid and other products.
The pyrolignites or acetates and the bisulphate of soda may be mixed in
apparatus, ordinarily in use for distillation of acetic acid. Care is to be taken
that the mixture should be uniform and that such vapours of acetic acid as may be
generated during the mixing should be properly condensed.
Where the pyroliguites or acetates and the bisulphate of soda are employed
in a solid form, it is advisable to add some water to aid the mixing and the
decomposition.
The distillation can be effected in apparatus such as is usually employed for
the production of acetic acid, with or without reducing the pressure within the
still during distillation.
If the distillation is carried on under reduced pressure, the end of the condenser
pipe should be hermetically connected to a recipient of suitable dimensions, the
pressure in which is reduced by means of an air pump or otherwise. In this
recipient the acetic acid collects, being distilled more rapidly and at lower
temperature than when under ordinary pressure. Between the air pump or other
aspirator and the recipient it is advisable to put a second recipient containing a
suitable base, either solid or in solution, so as to avoid any loss of acetic acid.
When the distillation of the acetic acid becomes slow, there should be added to
the mixture in the still either water or diluted acetic acid obtained from a previous
distillation, or steam, and the mixture should be agitated in introducing the steam.
After the said addition, the distillation is resumed and continued until, when
it becomes slow again, a fresh addition is made of water, steam or diluted acid.
According to the degree of concentration of the acid which is desired, the
products of the distillation are variously fractionated, adding to the mixture in the
still more or less water or steam or diluted acid, and reducing more
the pressure in the still, should the distillation be carried on under reduced
pressure.
or less
The last traces of acetic acid can be expelled from the still by a current of air, or
of steam or of air and steam mixed.
The residuum which is found in the still after the last traces of acetic acid
are expelled can be utilized for the manufacture of sulphate of soda. And this
last product is easily obtained by making the said residuum into a solution, which
after being filtered is left to crystallize.
Distillation under reduced pressure may be applied to the drying and distillation
of wood, and the distillation of raw pyroligneous acid.

page_text: Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The herein described process for manufacture of acetic acid by decomposing
pyrolignites or acetates by bisulphate of soda.
2. The utilisation of the residuum of the manufacture above referred to, for the
production of sulphate of soda, substantially as described.
Dated this 12th day of December 1892.
ABEL & IMRAY,
Agents for the Applicants.