Improvements in the Process for Freeing Kips, Skins, and Hides from Lime, and for Causing the same to Swell.
Year: 1889

page_text: Date of Application, 7th Aug., 1889-Accepted, 26th Oct., 1889
COMPLETE SPECIFICATION.
Improvements in the Process for Freeing Kips, Skins, and Hides
from Lime, and for Causing the same to Swell.
I, JULIUS HAUFF, of Fuerbach near Stuttgart, Germany, Proprietor of Chemical
Works and Chemist, do hereby declare the nature of this invention and in what
imanner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
In the introduction of Cresotinic Acid for freeing very tender skins from lime, such
as sheep's or goat's skins, it has been found that its operation was liable to be too
powerful under certain circumstances.
Experiments were accordingly made with the Oxynaphthoic Acids which are soluble
in from 10000 to 30000 parts of water and which are highly suitable for freeing from
lime the coarse with the tender skins by allowing a correspondingly longer time for
the treatment of the former.
As Oxynaphthoic Acids should be understood the Carbonaceous or Carbon con-
taining Acids which can be obtained by the action of Carbonic Acid upon the Alkaline
compounds of a and ẞ Naphthol. It is obvious that other modes of producing the
said Carbon containing Acids are not hereby excluded.
Further, it has been found that in cases where no swelling action was required and
for heavier skins, the lime freeing treatment could be likewise carried out by means of
Salicylic Acid, mixtures of Salicylic Acid and Cresotinic Acid, of Salicylic Acid and
Oxynaphthoic Acid, or of Cresotinic Acid and Oxynaphthoic Acid, or of all the three
Acids, so long as the price thereof did not form any obstacle to its use.
The further result worthy of interest which has been observed in the lime freeing
process by means of Cresotinic Acid and Oxynaphthoic Acid is that of a far lesser
quantity of the above Acids is required for the removal of the lime from the skins,
kips and hides and hence for the settling of the same than corresponds to the neu-
tralization of the lime. This fact finds its explanation in the property possessed by
Cresotinic Acid and Oxynaphthoic Acid, of forming soluble basic lime compounds.
Practically the desired result may be obtained in a tan yard with an eighth part of
the quantity of Cresotinic Acid that would otherwise be required for neutralizing the
lime. In a tan yard it was found that skins swollen by lime contained about
1000 grammes of lime (Ca 0) and after the mordant or corrosive action had taken
place upon these 100 kilos of skins, the latter still contained 540 grammes of lime (Ca O).
The dissolved 460 grammes of Ca O would require for the production of the neutral
salt 2498 grammes of Cresotinic Acid but a quantity of only 300 grammes of Cresotinic
Acid or about one eighth of the whole was found necessary for the formation of the
neutral salt. By this treatment the skin had reached the necessary degree of freedom
from lime which was deemed sufficient by the Tanner while the leather manufactured
thereby bad all the required properties.
Furthermore, the experiments undertaken with neutral Cresotinic Acid and
Oxynaphthoic Acid (ie. other neutral salts of these Acids) have given results con-
firming the above figures.
The result thus obtained is that the price of Cresotinic Acid and Oxynaphthoic Acid
causes no obstacles to their use, but on the contrary they have in comparison with the
mordants hitherto used, great advantages in a pecuniary sense independent of the
antiseptic properties of these Carbonaceous or Carbon containing Acids which cannot
be too highly valued. I may also remark that as Cresotinic Acid must be understood
the Carbon containing or Carbonaceous Acids of the three Cresols. For strong
leathers such as sole leathers, mixtures can be taken of Cresotinic acid and Salicylic
acid consisting of equal parts of these acids or of unequal parts up to frds Salicylic
acid and 3rd Cresotinic acid, and according to these proportions, 1 to 3 grammes of

page_text: the mixtures of the acids are to be employed per kilogramme of hides, from which
latter the hairs have been removed.
For more soft hides, for sleeked leather, mixtures can be taken consisting of }rd
Salicylic acid and 3rds Cresotinic acid.
For tender hides only Cresotinic acid, or oxynaphthoic acid, or variable mixtures of
these two acids; for these kinds of hides it is also sufficient to take 1-3 grammes
of the single acids or mixtures per kilogramme of hides, from which latter the hair
had been removed.
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
claim is:
For the removal of the lime from skins, kips, and hides, the use of Oxinapthoic
Acid i.e. (of Carbon containing or Carbonaceous Acids produced by the action of
Carbonic Acid upon the Alkaline compounds of a and ẞ Napthol or in any other
suitable manner) as well as of Salicylic Acid, or of mixtures of Cresotinic Acid and
Salicylic Acid, of Salicylic Acid and Oxinapthoic Acid, of Cresotinic Acid and
Oxinapthoic Acid, or of all the three Acids, as well as of the soluble and non basic
salts of the said Acids.
Dated this 7th day of August 1889.
H. GARDNER,
166, Fleet Street, London, Agent for the said Julius Hauff.