IMPROVEMENTS IN TANNING
Year: 1855

page_text: TIER
Aug
Loradoux Derord, or 32, Essex
Street, Strand, London, Patent Agent, for the Invention of "IMPROVEMENTS
IN TANNING." A communication from Messrs. Rene de Kercado Molac
and Jean Daniel Friedel, both of Strasbourg, Empire of France.
Sealed the 13th March 1855, and dated the 12th January 1855.
Bellford, at the Office of the Commissioners of Patents, with his Petition
and Declaration, on the 12th January 1855, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
I, AUGUSTE EDOUARD LORADOUX BELLFORD, of 32, Essex Street,. Strand,
London, Patent Agent, do hereby declare the nature of the said, Invention for
"IMPROVEMENTS IN TANNING," a communication from Messrs. Rene de Kercado
Molac and Jean Daniel Friedel, both of Strasbourg, Empire of France, to be
as follows, viz. :-
This Invention relates to an improved system of mineral tanning, by which
the required flexibility, tenacity, and weight is imparted to the hides and skins
treated. Various mineral compounds have been proposed for obtaining this
purpose, but the results arrived at were not such as to allow thein being suc-
cessfully introduced in lieu of the common vegetable and bark tanning process;
as the leather treated by those processes did not possess the above qualities,
being liable to tear in length of time on account of the great quantity of acid
remaining in the leather corroding the animal fibres.

page_text: The principle of this improved system is the use and application of peroxyd
(otherwise called sesquioxyd) of iron, this oxyd being made to form under
certain circumstances a stable compound with gelatine.
Before entering upon the practical modes of applying said principle, I will
first state some theoretical observations on the action of iron salts upon gela-
tinous matters. It is known that upon skins or hides being put in presence
of a salt of peroxyd or sesquioxyd of iron, a combination of the gelatine of said
skin takes place with the iron salt. Attempts have been made at using this
combination for tanning, but no satisfactory result was arrived at. However,
if the hides be left a certain length of time in the solution of iron salt, and an
oxyd be added which does not decompose the salt, the gelatine which forms
the skin goes on absorbing an indefinite quantity of sesquioxyd of iron, the
quantity of acid at the same time diminishing indefinitely in the hides, which
are thus converted in leather or skins, that may be cured in the same way.
From this action it results that the combination of gelatine with the salt of
peroxyd of iron is unstable, the acid of the salt being liberated by degrees;
also a more stable combination of the peroxyd of iron takes place, this con-
bination being facilitated by the presence of an oxyd, which, by absorbing the
acid as it is set free; keeps the tanning liquor in the neutral state, which is
necessary for operating. This stable compound is obtained by means of any
chemical compound by which the gelatine of the leather is brought into the
presence of a salt of peroxyd of iron capable of combining with it, and at the
same time of an oxyd, which, without decomposing the iron salt, shall absorb
the acid as it is set free from the unstable combination of gelatine with the iron
salt, those two ingredients producing finally a stable combination of gelatine
and peroxyd of iron, the solution or liquor being kept neutral or nearly so by
the absorbing action of the oxyd. The iron salts that combine with gelatine
being very numerous, I shall only mention the less expensive ones, viz., the
sulphate, nitrate, and acetate of peroxyd of iron, also the per-chloride and
pyrolignite of iron. The absorbing oxyds which may be used as being less
expensive are equally numerous, such as the oxyds of iron, manganese,
alumina, zine; other oxyds may also be used, but they will be found to require
greater care in manipulating than those named.
Having thus briefly set forth the nature of this Invention, I will now
proceed to shew the manner in which the same is or may be practically
carried out.
Of all the chemical compounds and oxyds above alluded to, by which the
desired effect may be produced, sulphate of peroxyd of iron and the peroxyd of
iron itself will be found preferable, on account of their simplicity and cheap-

page_text: ness.
In order to produce these two principal ingredients, I use a solution of
sulphate of iron, bioxy (otherwise peroxyd) of manganese, and sulphuric acid,
as shown on the right-hand side of the chemical equation below. These
substances being employed in such proportions as to leave a portion of the
oxyd of iron precipitated in the liquor, form the proper ingredients to be used
as a tanning solution, as shewn on the left side of the following equation:-
3 SO3, Fe 0+2 (SO³, Mn. O) + Fe² 0 = 4 (SO³, Fe.O) + 2 Mn. 02 +SO³.
To this liquor is added a certain quantity of pyrolignite of iron, which acts
as a tanning matter, like the sulphate of peroxyd of iron, and also gives to the
leather a brownish colour, whose intensity may be made to vary according to
the quantity of pyrolignite employed. The raw hides, skins, etc., having been
washed in the usual way, are then steeped in the tanning vats containing the
tanning liquor, above described. This part of the process being the same as
with common bark tanning, the liquors first used must be weak, and then
increase towards the end of the treatment to 15 or 18 degrees of solution.
When the hides are in the tan vats, fermented barley is added; also when the
liquor gets slightly exhausted or acidulated, it will be convenient to add to it
hydrated oxyd of iron for neutralizing said liquor. As to the proportions in
which these two matters have to be applied, they can only be determined by
experiments. After the hides have thus been left steeping in vats for about
three or four weeks, they are put into pits for the same length of time, taking
care to keep them asunder by bodies that let the tanning liquor circulate
between them, such as laths, light planks, straw, sand, coal, or any other mate-
rial not liable to affect or alter the leather. The hides having been thus laid in
piles, the pits are completely filled with tanning liquor, the strength of which
is successively and by degrees raised from twenty degrees to the maximum
strength the liquor may be made of. During the time the hides are lying in
the pits, they must be subjected to a pressure which is taken off from time to
time, and whose amount shall be in proportion to the concentration of the
solution. This pressure, which is obtained by means of a plate acted upon by
wedges, or a screw, &, is intended to prevent any extraordinary swelling of
the hides, quickening at the same time the action of the tanning liquid, by
causing it thoroughly to penetrate the hide. Contrary to the mode practised
in ordinary tanning, the hides when taken out of the tan pits must be com-
pletely washed out by any suitable means used to that effect, such as a
fulling apparatus. This washing operation must be carried on until the water
that runs off contains neither acid nor salt. This may also be effected by
exposing the tanned hides to the action of a flowing river for some days. For

page_text: certain kinds of leather that are not to be greased much, the washing process
is terminated by treating the skin with soap water, or with a solution of any
cheap organic or inorganic alkali, such as glycerine, soda, &. The lavatory
process finishes the tanning, which may last from six weeks to two months,
according to the thickness of the hide, or the concentration of the tanning
liquor employed. The hides after having been washed are dried, and then
dressed according to the usual methods. The leather obtained by the tanning
process described has the same appearance and qualities. as bark-tanned
leather; moreover, it is found to possess a greater cohesive strength, its exten-
sion being considerably less under a given weight or traction. The processes
above described may also be applied to tanning or curing skins that are to be
used as furriery.
Having thus described the nature of this Invention, and the manner in
which the same is or may be performed, I wish it to be distinctly understood
that what I claim as novel, and beeing secured to me by the herein-before in
part recited Letters Patent, is, the use and application of the peroxyd of iron
for tanning hides and skins, by causing said peroxyd to form a stable compound
with gelatine, in the manner substantially above described.
In witness whereof, I, the said Auguste Edouard Loradoux Bellford,
have hereunto set my hand and seal, this
day of January,
in the year of our Lord 1855.
A. E. LORADOUX BELLFORD. (L.S.)