Improved Means and Process for Removing Lime from Skins and Hides.
Year: 1894

page_text: Date of Application, 21st Nov., 1894-Accepted, 22nd Dec., 1894
COMI LEIE DI PULICATION.
Improved Means and Process for Removing Lime from Skins
and Hides.
I JULIUS HAUFF of Feuerbach, near Stuttgart, Germany, Manufacturer, 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 improved means and process for removing the lime from
and swelling all kinds of skins and hides, consisting in subjecting the skins and
hides to the action of one of the following sulphonic acids or a mixture of one of
the said acids with free sulphuric acid: The sulphonic acids of the aromatic hydro-
carbons, such for instance as benzol, toluol, xylol, naphthalene, antracene, and
phenanthrene; the sulphonic acids of the hydroxyl derivates of the aromatic
hydrocarbons such as phenol, cresols, xylenols, naphtols, oxyanthracenes and
oxy-phenanthrenes; the sulphonic acids of the aromatic carbonic and oxycarbonic
acids, such as benzoic acid, phtalic acid, salicylic acid, cresotinic acids, oxy-
naphtoic acids, the sulphonic acids of aniline, toluidines, xylidines and naphtyl-
amines.
Free sulphuric acid does not form a suitable means for freeing skins and hides
from lime on account of its caustic properties I have found however that the
sulphonic acids, which all form soluble lime salts, may be advantageously employed
in tanning as a mordant for freeing skins and hides from lime, firstly because in
these acids the caustic properties of the free sulphuric acid are neutralized and
then again because they possess more or less antiseptic and albumen coagulating
properties, thus preserving the skins before and during the tanning.
A solution or mixture of the respective sulphonic acid with water in the
proportion of 1:500 is advantageously employed, in which the skins are placed at a
temperature of about 30° C. and allowed to remain from 1 to 2 hours according to
the weight of the skins, the said solutions or the skins being stirred or suitably
kept in motion during this time. After this operation all lime will be found to have
been extracted from the skins.
When freeing skins from lime which have not been previously scraped, i.e. skins
possessing their full amount of lime, a mixture of the sulphonic acid with varying
quantities of free sulphuric acid is advantageously employed, for instance this
mixture as it occurs as raw product in the manufacture of the sulphonic acids.
In this case first the free sulphuric acid will act on the lime at the upper surface
of the skin and be neutralised immediately to gypsum which latter may, by
subsequent treatment be rinced off the skin. Not until this neutralisation of the
free sulphuric acid has taken place will the sulphonic acid be able to act on the
lime more closely set in the said skin, entirely dissolving the same.
After the skin or hide has been freed of lime the swelling process may take
place in a fresh solution of sulphonic acid and water in the proportions of 1:500, as
is necessary for the purpose of preparing sole leather. As the sulphonic acids, on
account of their marked properties of coagulating albumen have no solvent effect
on the substance of the skins or hides itself, this treatment gives a very favorable
result in respect of weight. By entirely dissolving out the lime from the true
skins, and owing to the sterilisation which takes place during the corroding operation,
the leather obtained by the present process attains great strength, is soft grained
and has a light colour.

page_text: The sulphonic acids of such cresols, which are obtained as bye-product in the
manufacture of carbolic acid, are most suitable for freeing the hides from lime and
for the corroding operation, on account of their easy obtention and consequent
cheapness, and more particularly on account of their eminent antiseptic properties.
Thus in order to obtain an exceedingly cheap and effective mordant f.i. 100 ko. cresol
and 200 ko. of 96% sulphuric acid should be heated to a temperature of 100° in a
water bath for a few days, then diluted with 300 litres of water and allowed to
stand until the resinous impurities have separated out.
The light liquid thus obtained is ready for use.
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 :-
The improved means and process for removing the lime from and swelling all
kinds of skins and hides, consisting in subjecting the skins and hides to the action
of one of the following sulphonic acids or a mixture of one of the said acids with
free sulphuric acid: The sulphonic acids of the aromatic hydrocarbons, such for
instance as benzol, toluol, xylol, naphthalene, antracene and phenanthrene; the
sulphonic acids of the hydroxyl derivates of the aromatic hydrocarbons such as
phenol, cresols, xylenols, naphtols, oxyanthracenes and oxy-phenanthrenes; the
sulphonic acids of the aromatic carbonic and oxycarbonic acids, such as benzoic
acid, phtalic acid, salicylic acid, cresotinic acids, oxynaphtoic acids, the sulphonic
acids of aniline, toluidines, xylidines and naphtylamines.
1004
H. GARDNER,
Patent Agent, 166, Fleet Street, London,
Agent for the said J. Hauff.
H. GARDNER,
Patent Agent, 166, Fleet Street, London,
Agent for the said J. Hauff.