Year: 1899

page_text: I, FRANZ WALTHER WARTENBERGER, of 40, Langereihe, Hamburg, in the Empire
of Germany, Merchant, do hereby declare the nature of this invention to be as
follows:-
This invention relates to a tanning process which is carried out by the use of
highly diluted solutions of picric acid as a tanning liquor in which the hides or
skins prepared in the usual manner are subjected to a first dressing and which are
then after a few hours finished off.
The peculiar feature of this process consists in that the picric acid is only used
when highly diluted with water. The strongest solution used contains only 1 part
of picric acid to 70 parts of water, but weaker solutions are usually preferred.
The use of picric acid for practical tanning purposes is only possible when used
in a very weak solution indeed. While strong solutions of picric acid render
the tanning process too costly and also unduly attack the hides or skins, a weak
solution renders it cheap and gives excellent results.
The process in itself is simple and consists in steeping the hides or skins pre-
viously prepared in a well known manner, for about two to four hours in a weak
solution of picric acid, this treatment being suitable for hides which are to be
finished off at once. These tanned hides or skins if desired on being removed
from the liquor, are then rinsed in a watery solution of antichlor (hyposulphite
of soda) then washed and finally treated in the usual manner. The antichlor has
the effect of giving the tanned leather a slightly lighter shade than usual, and to
fix the picric acid.
Heretofore whenever phenols, to which also belong picric acid, have been
employed in the tanning process it has only occurred in combination with other
chemical agents.
For example it has been proposed to employ carbolic acid in connection with
alum, culinary salt, aluminium salts and the like for tanning purposes, but here
the carbolic acid only plays a secondary part. Taken by itself the carbolic acid
is devoid of tanning qualities as has been frequently demonstrated by experiment.
Amongst the phenols however picric acid has been found to constitute quick
acting and useful tanning agent providing it is used as hereinbefore described in
weak solutions.
Dated th: ALL
E L
2
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: I, FRANZ WALTHER WARTENBERGER, of 40, Langereihe, Hamburg, in the Empire
of Germany, Merchant, 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: —
This invention relates to an improved process of tanning which is carried out
by the use of highly diluted solutions of picric acid as a tanning liquor, in which
the hides or skins, previously prepared, that is, bated and depilated in the usual
manner, will be tanned so rapidly that after having been treated for a few hours
the hides are thoroughly tanned and converted into leather, which, after a. subse-
quent treatment with a watery solution of hyposulphite of soda, may be imme-
diately curried or dressed by beating, running, and scraping in the usual manner,
in order to fit the hides, or the leather proper,, for the purpose for which it is
intended.
The neculiar feature of this process consists in that the picric acid is only used
when highly diluted with water. The strongest solution employed containing
only about 1 part of picric acid to about 70 parts of water, but weaker solutions
are usually preferred.
The use of picric acid for practical tanning purposes is only possible when
need in a very weak solution according to this invention. While strong solutions
of picric acid render the tanning process too costly, and also unduly attack the
hides or skins., a weak solution renders it cheap and gives excellent results. +
The process in itself is simple, and consists in steeping the hides or skins, they
having been previously bated and depilated, in a weak solution of picric acid
as explained above, at ordinary temperature, which in some cases may be raised
to about 30° C. and maintained at this temperature during the process of tanning.
The duration of the tanning process or tanning operation depends upon the nature
and strength of the hides and varies accordingly. I have. however, found that a
good leather is obtained by subjecting the hides to the action of the said diluted
picric acid solution generally for about two to four hours. When the hides are
thoroughly tanned and converted into leather, they are removed from the tanning
liquor, and subjected to a subsequent treatment, which consists in rinsing the
hides, or leather proper, in a solution of about 100 parts of water and about 30 parts
of hyposulphite of soda or the like. This latter solution has the effect of giving
the tanned leather a slightly lighter shade than usual, and of fixing the picric acid.
thus depriving it of its discolouring and poisonous qualities: After this treatment
the leather is washed and then curried in the usual manner.
Heretofore wherever phenols, to which also belongs, picric acid, have been*
employed in the tanning process it has only occurred in combination with other
chemical agents.
For example, it has been proposed to employ carbolic acid in connection with
alum, culinary salt (sodium chloride), aluminium salts and the like for tanning
purposes, but here the carbolic acid only plays a secondary part. Taken by itself
the carbolic acid is devoid of tanning qualities as has been frequently demonstrated
by experiment. Amongst the phenols however, I have found picric acid to con-
stitute a quick acting and useful tanning agent, providing it is used in weak
solution as herein before described.

page_text: Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The improved process of tanning which consists in steeping the bated and
depilated hides in a weak solution of picric acid in about the proportion of 1 part
of picric acid to not less than 70 parts of water, substantially as and for the
purpose forth.
2. The improved process of tanning, which consists in tanning the bated and
depilated hides or skins in a weak solution of picric acid and in subsequently
treating the tanned hides or leather respectively in a solution of hyposulphite of
soda, substantially as and for the purpose specified.
Dated this 16th day of November 1899
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.