IMPROVEMENTS IN THE PREPARATION OF TANNIC EXTRACTS
Year: 1883

page_text: LETTERS PATENT to John Henry Johnson of 47 Lincolns Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
THE PREPARATION OF TANNIC EXTRACTS" communicated to him from Emilo
Louis Paul Coëz and Gustave Clément Coëz persons resident at St Denis
in the Republic of France
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 26th June 1883.
JOHN HENRY JOHNSON, of 47 Lincolns Inn Fields in the County of Middlesex,
Gentleman, "IMPROVEMENTS IN THE PREPARATION OF TANNIC EXTRACTS," a
communication to me from Emile Louis Paul Coëz and Gustave Clément Coëz,
persons resident at St Denis in the Republic of France,
"
The tannic extracts heretofore supplied to tanners are to a certain extent
rendered colourless by various processes but are imperfectly freed from the
colouring matter which they contain, this matter being in fact merely neutralized
by chemical agents and liable to reappear at any time under certain conditions
such as age or exposure to the air for example-According to this invention the
tannic juices are deprived of colour by removing the colouring matter instead of
simply neutralizing it as in the processes usually employed.
This result is obtained as hereinafter described. The tanning matter or juices
being extracted or obtained by the usual processes the decoctions are placed in
wooden vessels in which they are immediately subjected to the process of
decolorisation in the following manuer, namely -Oxalic acid is first added in
the proportion of one grain of acid to every hundred litres of juice (the density
of the latter is of little moment) for the purpose of saturating the lime which
is contained in the water used in the process of extraction in proportions varying
according to the quality of the said water. After allowing a few minutes for
the oxalic acid to act alumina is introduced in the proportion of about two
D

page_text: hundred and fifty grains of alumina per hundred litres of juice and per degree
of density. For this purpose it is preferred to employ alumina in the condition of
jelly.
The materials are now violently agitated and the mixture being filtered
immediately thereafter the alumina remains upon the filter together with the
coloring matter. The clear tannic juice from which the colouring matter has
thus been removed is collected and evaporated in vacuo by known means and
brought to a density of about twenty degrees Beaumé.
The tannic extract obtained by means of this process is remarkably pure, fluid,
soluble and readily assimilated by hides or skins.
In order to produce tannic acid by this process the proportion of alumina
herein before indicated must be quadrupled This increase in the quantity of
alumina has the effect of causing the colorless extracting and mucilaginous matter
to be absorbed (which matter may be allowed to remain without disadvantage in
the extract used in tanning): A-solution of tannic acid is thus obtained which is
also evaporated to a density of about twenty degrees Beaumé.
This process is applicable to all vegetable matter containing tannin, such as
wood, bark, leaves, husks, and the like.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Henry Johnson in the Great Seal Patent Office on the
24th December 1883.
"
"
ก
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN THE PREPARATION OF TANNIC EXTRACTS
communication to me from Emile Louis Paul Coëz and Gustave Clément Coëz
persons resident at Paris in the Republic of France
The Tannic extracts heretofore supplied to tanners are to a certain extent
rendered colorless by various processes but the great defect of these extracts is
that they are imperfectly freed from the colouring matter which they coutain this
Inatter being in fact merely neutralised by chemical agents and liable to reappear
at any time under certain conditions such for example as age or exposure to
the air. According to this Invention tannic extracts or tannins are absolutely
deprived of colour by removing the coloring matter instead of simply neutralising
it as in the processes usually employed.
This result is obtained as hereinafter described. The tannic extracts being
extracted or obtained by the usual processes the decoctions are placed in wooden
vessels in which they are immediately subjected to the process of decolorisation in
the following manner namely. Oxalic acid is first added in the proportion say
of about half a dram (one gram) of acid to about twenty gallons (hundred litres)
of the decoction (the density of the latter is of little moment) for the purpose of
saturating the lime which is contained in the water used in the process of
extraction in proportions varying according to the quantity of the said water.
After allowing a few minutes for the oxalic acid to act, alumina is introduced
preferably in the proportion of about eight and three quarter ounces (two hundred
and fifty grams) of Alumina to cach twenty gallons (hundred litres) of the liquid
and degree of density. For this purpose it is preferred to employ alumina recently
prepared in tho condition of jelly.
The materials are now violently agitated and the mixture is filtered immediately
after so that the alumina remains upon the filter together with the coloring matter.
The clear tannic extract from which the coloring matter has thus been removed
is collected and evaporated in vacuo by any suitable known means for effecting such
purpose and brought to a density of about twenty degrees Beaumé. The tannic
extract or tannin obtained by means of this process is remarkably pure, fluid and
soluble and is readily assimilated by hides or skins.
In order to produce an extract consisting of tannic acid according to this
Invention the proportion of Alumina added to the liquid as herein before indicated
must be increased (preferably quadrupled). This increase in the quantity of
Alumina has the effect of causing the colorless extractive and mucilaginous matter
to be absorbed (which matter may be allowed to remain without disadvantago in
the extract used in tanning). A solution of tannic acid is thus obtained which is
also evaporated to a density of about twenty degrees Beaumé.
This process is applicable to all vegetable matter containing tannin, such as
wood, bark, leaves, liusks and the like.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original

page_text: and therefore claim as the Invention secured to me by the hercinbefore in part
recited Letters Patent is :—
In the preparation of tannic extracts, tannic acids or tannins, the employment
of Alumina in the manner and for the purpose substantially as herein before
described.
In witness whereof I the said John Henry Johnson have to this my Specification
set my hand and seal this twentieth day of December One thousand eight bundred
and eighty three
J. HENRY JOHNSON (L.S.)