for Clarifying and Bleaching Tannin Extracts or Tanning Liquors.
Year: 1891

page_text: Date of Application, 11th Mar., 1891
Complete Specification Left, 8th Dec., 1891-Accepted, 9th Jan., 1892
PROVISIONAL SPECIFICATION.
Process for Clarifying and Bleaching Tannin Extracts or
Tanning Liquors.
I, Dr. AUGUST FOELSING, Manufacturer, of Düsseldorf, Germany, do hereby
declare the nature of my invention to be as follows:-
The liquors obtained by the extraction of vegetable products containing tannin,
such as chestnuts, oak bark, divi-divi, are brought to a density corresponding to
4° Beaumé at 171° Centigrade, and drawn off into a tank, after which oxalic acid
and sodic chloride dissolved separately, are added in the proportion of 500 grammes
of oxalic acid and 2 kilos. of sodic chloride to 10,000 litres of tannin-liquor.
The liquid mixture or solution thus obtained is then heated to 60° Centigrade
and subjected to electrolysis. The electric current, besides decomposing the oxalic
acid and the sodic chloride, produces between the two poles the separation and
cloudy or
precipitation of resins, cellulose and colouring matter in the shape of a
Haky deposit.
The strength of the current depends on the quantity of the liquid to be clarified
and on the time, in which the operation is to be completed.
The electrodes are made of platinum and have the shape of wire-netting mounted
on a wooden frame.
Dated this 9th day of March 1891
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Process for Clarifying and Bleaching Tannin Extracts or
Tanning Liquors.
I, Dr. AUGUST FOELSING, Manufacturer, of Düsseldorf, Germany, 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 liquors obtained by the extraction of vegetable products containing tannin,
such as chestnuts, oak-bark, divi-divi, are brought to a density corresponding
to 4° Beaumé at 17° Centigrade, and drawn off into a tank, after which
oxalic acid and sodic chloride, dissolved separately, are added in the proportion
of about 500 grammes of oxalic acid and 2 kilos. of sodic chloride to 10,000 litres
of tannin-liquor.
The liquid mixture or solution thus obtained is then heated to 60° Centigrade
and subjected to electrolysis. The electric current, besides decomposing the oxalic
acid and the sodic chloride, produces between the two poles a voluminous deposit,
which consists chiefly of resins, cellulose and colouring matter, that is to say,
substances other than tannin.
The strength of the current, which may be produced by a small dynamo-machine,
depends on the quantity of the liquid to be clarified and on the time in which the
operation is to be completed.
For instance, 10,000 litres of liquid, of 4 degrees Beaumé and at a temperature
of 50 degrees Centigrade, would, as a rule, require a current of about 14 volts
and
amperes, but the strength of current is inversely proportional to the time,
that is to say, the more rapidly the clarifying process is to be performed, the
stronger must be the current.

page_text: The electrodes may be made of platinum and have the shape of wire netting
mounted on a wooden frame.
For the above mentioned quantity of 10,000 litres the height of the tank
would preferably be about 15 metres, and the width 1 metre; the weight of each
electrode without the frame, (that is to say, only the platinum) would be about
500 grammes, and the distance of the electrodes from each other about 3 metres.
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:
The process for clarifying and bleaching tannin extracts or tanning liquors,
which consists in bringing the crude extracts to the required density, adding
solutions of oxalic acid and sodium chloride, heating, if necessary, and subjecting
the mixture to electrolysis, substantially as described.
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1001
AUG. FOELSING,
By Fairfax & Wetter,
433, Strand, London, Agents.
AUG. FOELSING,
By Fairfax & Wetter,
433, Strand, London, Agents.