An Improved Process of Producing Methyleneditannic Acids from Formaldehyde and Tannin.
Year: 1896

page_text: Date of Application, 11th Jan., 1896
Complete Specification Left, 19th Sept., 1896-Accepted, 24th Oct.. 1896
PROVISIONAL SPECIFICATION.
An Improved Process of Producing Methyleneditannic Acids from
Formaldehyde and Tannin.
1, ERNST DÜRKOPF, Chemist to the Firm of E. Merck of Darmstadt, in the
Empire of Germany, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to produce new products which are products of
condensation from formaldehyde and tannin and which may be extensively used ou
account of their disinfecting and other qualities.
These products of condensation are according to this invention obtained by
passing formaldehyde in a gaseous form into a solution of a tannin or by adding an
aqueous solution of formaldehyde to such tannin solution.
A condensing agent, for example concentrated muriatic acid is then added, and a
new chemical compound is separated which may be considered as a methylene-
ditannic acid, as will be hereinafter explained by example.
Instead of using the pure tannic acid solution, the aqueous extracts from
the vegetable substances containing the respective tannin may be directly
employed.
1. Methyleneditannic acid of the gallotannic acid forms a reddish-white light
powder which becomes decomposed at a temperature of about 230 degrees
Centigrade, which on the one hand is insoluble in water and the usual organic
solvents with the exception of alcohol, and which on the other hand is soluble
with brownish red or yellow colour in dilute caustic liquor of soda, soda solution
or ammonia solution, and which is re-eliminated from these solutions by means
of acids. The compound dried at 102 degrees Centigrade is of the following
composition

page_text: EXAMPLE:
15 kilogrammes of the respective tannic acid (such as described as an example
in the paragraphs 2, 3 or 4) are dissolved in 100 kilogrammes of water, and
15 kilogrammes of a formaldehyde solution of 40 per cent., and concentrated
muriatic acid is added until the precipitation is completed (about 20 to 30 kilo-
grammes according to the nature of the tannic acid employed). The precipitate
is washed in the filter-press, separated by pressure and dried at a moderate
temperature.
In this manner the new methyleneditannic acids can be obtained from all those
compounds which are designated as tannic acids. It may be moreover mentioned
as examples that the methyleneditannic acid of the oak bark, methyleneditannic
acid of the pine bark, methyleneditannic acid of the walnut-shell, methyleneditannic
acid of catechu and so forth, have been produced.
Dated this 11th day of January 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
An Improved Process of Producing Methyleneditannic Acids from
Formaldehyde and Tannin.
I, ERNST DÜRKOPF, Chemist to the Firm of E. Merck, of Darmstadt, in the
Empire of 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 object of this invention is to produce new products, which are products of
condensation from formaldehyde and tannin and which may be extensively used on
account of their disinfecting and other qualities.
These products of condensation are according to this invention obtained by
passing formaldehyde in a gaseous form into a solution of a tannin or by adding an
aqueous solution of formaldehyde to such tennin solution.
A condensing agent, for example concentrated muriatic acid is then added, and
a new chemical compound is separated which may be considered as a methylene-
ditannic acid, as will be hereinafter explained by example.
Instead of using the pure tannic acid solution, the aqueous extracts from the
vegetable substances containing the respective tannin may be directly employed.
1. Methyleneditannic acid of the gallotannic acid forms a reddish-white, light
powder which becomes decomposed at a temperature of about 230 degrees
Centigrade, which on the one hand is insoluble in water and the usual organic
solvents with the exception of alcohol, and which on the other hand is soluble
with brownish red or yellow colour in dilute caustic liquor of soda, soda solution
or ammonia solution, and which is re-eliminated from these solutions by means
of acids. The compound dried at 102 degrees Centigrade is of the following
composition.
C29 H20018
and is to be considered as a methyleneditannic acid;

page_text: EXAMPLE:
5 kilogrammes of tannin are dissolved in hot water, to which 10 kilogrammes of
a solution of formaldehyde of 30 per cent. is added, and subsequently concentrated
muriatic acid is added as long as a precipitate is formed. This precipitate is
separated by pressing, washed and dried at a moderate temperature.
2. Methyleneditannic acid of the myrobalans tannic acid forms a brownish
yellow powder which in its qualities is similar to the methyleneditannic acid of the
tannin.
3. Methyleneditannic acid from quebracho tannic acid is a reddish brown powder.
which, when heated up to 275 degrees Centigrade, turns black without apparent
foaming effect and does not dissolve either in water in the usual organic solvents,
or in ammonia solution, soda solution and dilute caustic liquor of soda.
4. Methyleneditannic acid from ratanhia tannic acid is a brownish yellow powder
which presents similar qualities to the before described product.
EXAMPLE:
15 kilogrammes of the respective tannic acid (such as described as an example
in the paragraphs 2, 3 or 4) are dissolved in 100 kilogrammes of water, and
15 kilogrammes of a formaldehyde solution of 40 per cent., and concentrated
muriatic acid is added until the precipitation is completed (about 20 to 30 kilo-
grammes according to the nature of the tannic acid employed). The precipitate
is washed in the filter-press, separated by pressure and dried at a moderate
temperature.
In this manner the new methyleneditannic acids can be obtained from all those
compounds which are designated as tannic acids. It may be moreover mentioned as
examples that the methyleneditannic acid of the oak bark, methyleneditannic acid
of the pine bark, methyleneditannic acid of the walnut-shell, methyleneditannic
acid of catechu and so forth, have been produced.
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 :-
First. The manufacture of methyleneditannic acids, that is to say products of
condensation from tannins and formaldehyde by adding a condensing agent, for
instance concentrated hydrochloric acid, to a mixture of formaldehyde and a
solution of tannin.
Second. As new and practically useful products, the products of condensation
from tannins and formaldehyde, such as may be obtained according to the first
claim, substantially as set forth in the foregoing description.
Dated this 19th day of September 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.