IMPROVEMENTS IN PROCESS FOR OBTAINING OR EXTRACTING TANNIN
Year: 1879

page_text: $5
LETTERS PATENT to Walter Alfred Barlow, of 6, St. Paul's Churchyard,
London, Patent Agent and Engineer, for the Invention of IMPROVEMENTS IN
PROCESS FOR OBTAINING OR EXTRACTING TANNIN." A communication from
abroad by Paul Gondolo, of Paris, France.
PROVISIONAL SPECIFICATION left by the said Walter Alfred Barlow at
the Office of the Commissioners of Patents on the 18th March 1879.
WALTER ALFRED BARLOW, of 6, St. Paul's Churchyard, London, Patent Agent
and Engineer. “IMPROVEMENTS IN PROCESS FOR OBTAINING OR EXTRACTING
TANNIN." A communication from abroad by Paul Gondolo, of Paris, France.
It is ordinarily well known that the vegetable material from which tannin is
extracted is treated by maceration, either cold or more often warm. According to
this Invention I also proceed by maceration, but with this essential difference, that
the water serving for the maceration is to be slightly acidulated by means of an acid,
of a salt, or of an acid salt, provided always that it is not of such nature as to modify
the physical or chemical character of the tannin. In carrying the Invention into
practice preference is given to sulphuric acid, from which the best results have been
obtained, and although the proportion may vary to a certain extent, according to
the more or less calcerous composition of the river or spring water employed, yet it
is found that 6 decigrammes of acid to the litre of water (about 9 grains acid to 1
pints water) will produce the desired result.
The acid decoctions thus obtained are finally treated by an alkali, but only in the
proportion strictly necessary for the purpose of neutralizing remaining free acid.
There may be employed an alkali either caustic or carbonated, or alkaline earths;
for example, if there has been employed the proportion of acid above indicated, it
has been found that about a gramme of carbonate of soda will suffice per litre of the
decoction for its successful treatment.
Further, it will be understood that if in the first operation there has been'
employed a large quantity of acid, it will be necessary to increase the quantity of
alkali proportionately.

page_text: The tannic extract that is obtained after concentration by this method is greatly
superior to those ordinarily found in commerce, but a still more complete result is
yet obtained according to the further carrying out of this process. Different indus-
tries are not able to employ other than extracts of tannin extremely fluid, very lightly
colored; and therefore to supply a product having these characteristics the decoction
after its treatment by the alkali is submitted to a third operation, which is that of
clarification.
This clarification is worked by the aid of blood, albumen, glue, gluten, or any
other vegetable or animal substance able to take up the natural colorants of wood
either by coagulation or by absorption. If a coagulent is employed the decoction is
brought to a temperature short of that at which the substance employed in the
clarification will congeal, so that it extends throughout the mass; the temperature
is then raised to the degree requisite to produce coagulation. The decoction is then
allowed to settle for about one hour, when it is drawn off, filtered, and concentrated
in the open air or in a vacuum of from 3 to 45° Béaumé.
The extract of tannin obtained by this process is richer in tannin, of greater solu-
bility, and of a yellow honey color, instead of, as in tannin extracts hitherto
obtained, which are all of a deep chesnut brown color, which prevents its general
use in tanneries.
It must be understood that this process is applicable to the extract of tannin
from, wood, roots, leaves, bark, husks, grains, fruits, and generally all kinds of vege-
table matters. containing tannin.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Alfred Barlow in the Great Seal Patent Office on the 18th
September 1879.
WALTER ALFRED BARLOW, of 6, St. Paul's Churchyard, London, Patent Agent and
Engineer. "IMPROVEMENTS IN PROCESS FOR OBTAINING OR EXTRACTING TANNIN."
A communication from abroad by Paul Gondolo, of Paris, France.
It is ordinarily well known that the vegetable material from which tannin is
extracted is treated by maceration, either cold or more often warm. According to
this Invention I also proceed by maceration, but with this essential difference, that
the water serving for the maceration is to be slightly acidulated by means of an acid,
of a salt, or of an acid salt, provided always that it is not of such nature as to modify
the physical or chemical character of the tannin. In carrying the Invention into
practice preference is given to sulphuric acid, from which the best results have been
obtained, and although the proportion may vary to a certain extent, according to
the more or less calcerous composition of the river or spring water employed, yet it
is found that 6 decigrammes of acid to the litre of water (about 9 grains to 1 pints
water) will produce the desired ŕésült.
'
The acid decoctions thus obtained are finally treated by an alkal, but only in the
proportions strictly necessary for the purpose of neutralizing remaining free acid.
There may be employed an alkali either caustic or carbonated, or alkaline earths;
for example, if there has been employed the proportion of acid above indicated, it
has been found that about a gramme (15.43 grains) of carbonate of soda will
Buffice per litre (1 pints) of the decoction for its successful treatment.
Further, it will be understood that if in the first operation there has been
employed a large quantity of acid, it will be necessary for the saturation to increase
the quantity of alkali proportionately.
The tannic extract that is obtained after concentration by this method is greatly
superior to those ordinarily found in commerce, but a still more complete result is
yet obtained according to the further carrying out of this process. Different indus-
tries are not able to employ other than extracts of tannin extremely fluid, very
lightly colored; and therefore to supply a product having these characteristics the
decoction after its treatment by the alkali is submitted to a third operation, which
is that of clarification.
This clarification is worked by the aid of blood, albumen, glue, gluten, or any
other vegetable or animal substance able to take up the natural colorants of wood,
either by coagulation or by absorption. If a coagulent is employed the decoction is
brought to a temperature short of that at which the substance employed in the
clarification will congeal, so that it extends throughout the mass; the temperature
is then raised to the degree requisite to produce coagulation. The decoction is then.
allowed to settle for about one hour, when it is drawn off, filtered, and concentrated
in the open air or in a vacuum of from 3° to 45° Béaumé.
The extract of tannin obtained by this process is richer in tannin, of greater
solubility, and of a yellow honey color, instead of as in tannin extracts hitherto
obtained, which are all of a deep chesnut brown color, which prevents its general
use in tanneries.
It must be understood that this process is applicable to the extraction of tannin
from wood, roots, leaves, bark, husks, grains, fruits, and generally all kinds of vege-
table matters containing tannin.
For certain kinds of vegetables containing large quantities of coloring matter com-
bined with the tannin this process may be advantageously modified as follows, the
order of the operations being somewhat inverted :-There is added directly to the
maceration bath, and at any desired moment of the operation, a quantity either of
the blood or any other coagulent or absorbant; 20 grammes (12-86 dwts.) of blood
to each kilogramme (2 lbs. avoirdupois) of the vegetable matter under treatment is

page_text: a good proportion. Then take the decoctions, that is to say, the resulting liquors,
from the maceration and add to them, at same time well stirring them, and at a
temperature of from 55° centigrade but not exceeding 80°, 1 gramine (15.43 grains)
of carbonate of soda, or an equivalent proportion of an alkaline salt, and 15 grammes
(9 dwts.) of blood. After that pour in little by little 6 decigrammes (9 grains)
of sulphuric acid, these last proportions being calculated for each litre (1 pints) of
the decoction. As soon as this last addition is made the deposit takes place in
flakes, wherein the salt of lime and the greater part of coloring principle is con-
tained. The liquor is then concentrated at from 3° to 45° Béaumé. It is hardly
necessary to state that the indicated proportions are given as examples, and are
those which in practice have been found to be the best.
Having now described the nature of the said Invention, and how the same may
be readily carried into practical effect, I claim,—
First. The employment of the substances described, together with the indicated
manipulations for the purpose, and constituting a new process of extracting tannin,
substantially as herein set forth.
Secondly. The new industrial product, being the clarified tannin resulting from
the herein described process.
In witness whereof, I, the said Walter Alfred Barlow, have hereunto set my
hand and seal, this Seventeenth day of September, in the year of our Lord
One thousand eight hundred and seventy-nine.