Year: 1891

page_text: Date of Application, 12th May, 1891-Accepted, 27th June, 1891
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The skins or hides or parts thereof are immersed in a warm or cold solution of
the acid of sufficient strength or of more than sufficient strength for the conversion
The
of the alkali existing in the hides or skins, or parts thereof, into the salts.
length of time the skins or hides are subjected to the action of the acid will vary
with different kinds of skins.
It is desirable for best results to use the acids as pure as possible, but good
results may be obtained even if the said acid contains some of the impurities
incident to its manufacture, such as free sulphuric acid or muriatic acid and salts or
both, together with traces of the naphtalin sulphonic acid salts or traces of metals
arising from the apparatus in which the acid is made.
We find that the naphtalin sulphonic acids, not only remove the lime from the hide
or skin, but on account of their antiseptic qualities or properties also act as a
preservative, and that skins may be preserved and transported in this stage of the
process of leather manufacture. This arrest and preservation of the skin in an
untanned state, yet partially manufactured, is what is known as pickling. Therefore
skins thus treated with these acids are not only freed from alkali but may be con-
sidered pickled, and may be transported in this condition and the tanning performed
in auother place.
10
The naphtalin sulphonic acids are best employed in a solution varying from 2%
to 5% in strength, although it may be used very much weaker or stronger; if
weaker its action is much slower, and there is very little necessity for making it any
stronger, the object being to use an excess from 2% to 4% over the amount
necessary to convert the alkali or alkaline salts used as a depilatory and contained.
in the hides or skins at the time of treatment into their naphtalin sulphonic acid
salts. A. theoretical amount may, however, be used, based on the amount of alkali
actually contained in the skins, but more satisfactory results may be obtained by
using an excess over the actual requirements.
The advantages resulting from the use of the naphtalin sulphonic acids may be
briefly stated as follows:-
Their marked antiseptic qualities which preserve the hide or skin and its parts
from dissolution or loss during the bating process.
Their avoidance of the introduction of bacteria into the tan solution or liquors
which is attendant upon common methods and upon the use of acids which induce
decomposition.

page_text: Their lack of action upon the hide structure itself, except as a preservative.
The extreme solubility of their salts.
Their lack of action with iron salts to produce a discoloration of the solution.
By the complete removal of the alkali or alkaline salts employed as a depilatory,
its action upon the hide or skin, fitting it for a rapid combination with the tanning
agent, and effecting in the hide or skin the lightest color of which the hide or skin
is capable of taking with the tanning agent employed.
The production. of the greatest weight of leather of which the hide or skin is
capable through the avoidance of loss of gelatine.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:
1. In the preservation and pickling of skins and hides, the employment of the
sulphonic acids of naphtalin as set forth.
'
2. In the art of bating skins and hides, the subjecting of the same to the action
of the sulphonic acids of naphtalin, substantially as specified.
3. The improvement in the treatment of skins and hides, which consist in
converting the alkali of the skins or hides into its salts by the action of the sulphonic
acids of naphtalin, as set forth.
Dated this 11th day of May 1801
H. B. BARLOW,
Agent for Applicants.