New or Improved Process for the Preservation of Extracts and Liquids Containing Tannin, and Used for Tanning Purposes, by Means of Creosol, Napthol, Creosotic Acids, Napthoic Acids, and their Soluble Salts, as well as a Process for Preserving Kips, Skins, or Hides by Means of Creosol, Napthol, and their Carbon Containing Acids in suitable Solution or Mixed with suitable Balanta
Year: 1888

page_text: New or Improved Process for the Preservation of Extracts and
Liquids Containing Tannin, and Used for Tanning Purposes, by
Means of Creosol, Napthol, Creosotic Acids, Napthoic Acids, and
their Soluble Salts, as well as a Process for Preserving Kips,
Skins, or Hides by Means of Creosol, Napthol, and their Carbon
Containing Acids in suitable Solution or Mixed with suitable
Balanta
1, JULIUS HAUFF, of Feuerbach, near Stuttgart, Germany, Proprietor of Chemical
Works and Chemist, 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 :-
It is generally known that taunin becomes split or cracked under the influence of the
oxygen from the air and particularly through the living process of a lower form of
organism in sugar, gallic acid, and other secondary products of decomposition, such as
the acids of Milk, of Butter, of Vinegar, and the like. Recent experiments made in
this direction have proved that the above causes were capable of entirely destroying,
within a few days, the tannin contained in the diluted solutions of that compound, such
as used for tanning purposes.
It is hence obvious that the tanner suffers thereby important losses in tanning
material, while the tanned article is so altered in its fundamental properties through
the action of the above acids carried out under such injurious conditions, that it some-
times ceases to be marketable.
In order to remedy the above defects, known antiseptics such as Phenol and Salicylic
Acid have already been resorted to. With the first substance, the action is so slight,
that its price fully precludes the use thereof. The Salicylic Acid on the other hand
has, when the decomposition of the tannic lye or solution is sought to be prevented, to
be employed in such doses, that it introduces by itself in the process the injurious hy-
action of an acid, and thus actually produces that which it was intended to avoid. Its
object is consequently only half fulfilled, as it defeats its own purpose. The mercurial

page_text: compounds operate in the most radical manner but they have however to be strictly
excluded on account of their poisonous properties, and as a continuous wetting of the
hands by the poisonous liquids can in practice seldom be avoided. It is almost
incomprehensible how the substitution of lodide of Mercury for the Sublimate can
have been recommended in a recent Patent, since the poisonous properties of the
Mercurial Salts still remain the same as heretofore. The experiments under-
taken on a large scale in tan-yards for the removal of lime by means of Creosotic Acid
have demonstrated that the liquids in which were immersed the kips, skins, or hidos
after this treatment in a solution of Creosotic Acid resisted decomposition and mouldi-
ness for a much longer time than had been observable heretofore. It appears therefore
obvious, that the small amount of Acids still left in the kips, skins, or hides has already
sufficed to energetically combat the above destroying influences.
Direct experiments with Creosotic Acid have demonstrated the above remarks in
the most conclusive manner. Added in the proportion of 1:2000 to the liquid requiring
to be preserved, the destruction or mouldiness herein before mentioned is completely
provented. This is effected yet in a higher degree than with Creosotic Acid, by
employing the two Oxi-naphthoic Acids which operate infallibly when diluted in the
proportions of 1 to 5000.
Similar, although not quite such important results can be obtained by the use of
Creosol and Napthol. Owing to the small solubility of those compounds which rapidly
disappears in the case of the Naphthoic Acid it is desirable to use them in the form of
their casily soluble salts, which operate even more efficiently than the acids.
The use of the compounds above mentioned for the preservation of tannic extracts
and tannin containing lyes or liquids is very simple. A suitable solution thereof can
be readily prepared by mixing the substances named with water and diligently stirring
the same, particularly when the soluble salts are made use of. In practice it is better
when these substances are not employed as salts to dissolve them in Alcohol and to
add this solution to the liquid requiring to be preserved while continuously stirring
the liquor. The price of Alcohol need not have inuch weight in small operations, as
the addition of the Alcoholic solution to the liquids which are constantly kept to their
standard by fresh quantities of extracts, is only necessary once.
The selection of the preserving means must therefore depond upon the fact whether
they can serve for the treatment of sweet or somewhat sour tannic lyes or liquids, in
the latter case, the use of Creosotic Acid is of importance as its sourness enables it to
effect the treatment of slightly sour liquids required for many varities of leather, with-
out there being any danger of its possessing the defects attached to Salicylic Acid and
to the above mentioned destroying acids, such as Lactic Acid, Acetic Acid, and the
like in consequence of their small solubility and of the small doses in which they have
to be used. For very sweet lyos, the salts of the Naphthoic Acids which are found in
commerce with a small excess of free Alkali are most suitable as a portion of the
acids already in existence is thereby neutralized.
The simplest method is to incorporate with the extracts, the necessary quantity of
the substance required for its future solution according to its strength and which are.
determined by the following calculation given here by way of example. Supposing
that 100 Kg. of an extract which contains 25% of tannin is required to be preserved,
this extract will have to be dissolved until a lye having a percentage of 5% is obtained.
The 100 Kilos of extract will consequently produce 500 Kilos of liquor for the full
preservation of which 100 gr. of Naphthoic Acid and Soda is required.
In this caso
for each 100 Kg. of extract 100 gr. of this substance will have to be added in order to
prevent the destruction of the tannin when diluted with five times its weight of
liquid.
The substances mentioned can be used advantageously for the preservation of kips,
skins, or hides as compared with other means of preservation, such as heretoforo usod.
These substances are either rubbed in their natural state over the kips, skins and hides,
or the latter are treated with aqueous or diluted Alcoholic solutions of the former and
subsequently dried. Or the above substances may be dissolved in Glycerine or melted
therewith. In all cases it is thereby rendered possible to preserve for years, kips,

page_text: skins and hides free from destruction and mouldiness for the purpose of proceeding
with their tanning later on.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
5 claim is
The preservation of tannic extracts and of tannin containing lyes, such as used for
tanning purposes by means of Creosol, Napthol, their soluble salts, their carbonaceous
acids and the soluble salts of the latter; further, the preservation of skins, kips and
hides by means of Creosol, Napthol and their carbonaceous acids in aqueous or
Alcoholic solution, or melted with Glycerine for the purpose of preserving the kips,
skins, and hides until they have to be tanned.
DL L
T
L
1000
H. GARDNER,
166, Fleet Street, London,
Agent for the said Julius Hauff.