AN IMPROVED PROCESS FOR UNHAIRING HIDES OR SKINS, AND FOR FURTHER TREATING THEM PREVIOUS TO TANNING
Year: 1877

page_text: LETTERS PATENT to Roger William Wallace and Carl Friedrich Claus, both of
the Chemical Works, Southall, in the County of Middlesex, for the Invention
of "AN IMPROVED PROCESS FOR UNHAIRING HIDES OR SKINS, AND FOR
FURTHER TREATING THEM PREVIOUS TO TANNING."
PROVISIONAL SPECIFICATION left by the said Roger William Wallace and
Carl Friedrich Claus at the Office of the Commissioners of Patents on the
26th July 1877.
"5
ROGER WILLIAM WALLACE and CARL FRIEDRICH CLAUS, both of the Chemical
Works, Southall, in the County of Middlesex. AN IMPROVED PROCESS For
UNHAIRING HIDES OR SKINS, AND FOR FURTHER TREATING THEM PREVIOUS TO
TANNING."
The first part of our Invention relates to unhairing or removing the hair or
wool from hides or skins. We employ for this purpose solutions of sulphide of
barium instead of the lime usually employed, and we plunge or immerse the
hides or skins in the same for a time, varying according to the strength of the
solution, from 1 to 48 hours. A small quantity of slacked lime may be added to
the solution, but we prefer to use the solution of sulphide of barium alone. If
the hides or skins to be treated are fresh market hides or skins, the time
required for unbairing them is much less than that required for dry or salted
bides.
We find it advantageous to immerse the hides or skins, especially those of the
latter kind, first into liquors which have been already used to bring about the action
of unhairing gradually, and to thoroughly soften them. For this operation nothing
will equal the old or used liquor in quick and beneficial action. Another result of
proceeding in this manner is that the loosening of the scurf is effected very advan-
tageously, and the operation of "skudding" is facilitated. For this purpose we
pass the hides or skins from the oldest to the freshest pit. By the action of

page_text: rather strong solutions of sulphide of barium upon the hair it is caused to come off
the hide in the form of a slimy gelatinous mass, whilst the pelt is not affected, that
is to say, it is not swelled as in the lime pits, and retains its natural suppleness.
For this reason the operation of "bateing" skins for dressing leather may either
wholly or partly be dispensed with.
In very much diluted solutions the hair is not destroyed, but the time required
for unhairing is much longer.
The solution of sulphide of barium we prepare by dissolving in water solid
sulphide of barium, produced by heating in a reverberatory furnace, or in closed
kilns in a temperature approaching a white heat, sulphate of baryta mixed with
carbonaceous matter.
To the solution of sulphide of barium, solutions of other sulphides, such as sulphides
of sodium or calcium, may be added.
For separating wool and hair from the pelt, without injuring or wetting the latter,
we use highly concentrated solutions of the sulphide of barium, and add thereto any
inert substance, such as plaster of Paris or clay, for the purpose of producing a thin
paste, which we apply by means of a mop or otherwise to the flesh side only of the
skin. The liquor penetrates the skin, and loosens the hair or wool on the other
side, so that it can be removed dry and uninjured.
We also use for unhairing, instead of a solution of barium, a solution of sulphide
of sodium only, but prefer to do so without the addition of lime, which has an
injurious action on the pelt. We prepare the same, preferably, by decomposing a
solution of sulphate of soda by means of sulphide of barium. Although solutions
of sulphide of sodium can also be produced by heating to a red heat a mixture of
sulphate of soda and carbonaceous matter, and dissolving the resulting mass in
water; we prefer the former method, since in the latter process there would be a
considerable loss of materials, incomplete decomposition, and a destructive action in
the furnace or vessels wherein the heating is effected; and furtherinore, the resulting
solution contains in solution considerable quantities of sulphide of iron, which stains
the bides.
We also produce a solution of sulphide of sodium suitable for unhairing hides by
treating alcali waste, especially after it has begun to heat after a few hours exposure
to air, with cold, or preferably with hot solutions of sulphate, or carbonate of soda.
We prefer sulphate of soda for its comparative cheapness; the so-called nitre cake
will answer our purpose.
Our Invention also comprises the further treatment of hides or skins, especially
when lime has been used for unhairing, as in the ordinary process. The object of
this part of the said Invention is to dispense with the use of hen or pigeon dung in
the process of "bateing," for which we use solutions of chloride of magnesium, and
also of chloride of calcium.
We have ascertained by analysis of water used in a tannery that it contains
noteable quantities of the above salts, and for the purpose of our Invention we
reproduce the same artificially, that is to say, by the use of solutions of the afore-
said salts, and thereby effect a result similar to that produced by the "bateing "
process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Roger William Wallace and Carl Friedrich Claus in the Great Seal
Patent Office on the 25th January 1878.
"
ROGER WILLIAM WALLACE and CARL FRIEDRICH CLAUS, both of the Chemical
Works, Southall, in the County of Middlesex. AN IMPROVED PROCESS FOR
UNHAIRING HIDES OR SKINS, AND FOR FURTHER TREATING THEM PREVIOUS TO
TANNING."
The first part of our Invention relates to unhairing or removing hair or wool
from hides or skins. We employ for this purpose solutions of sulphide of barium
instead of the lime usually employed, and we plunge or immerse the bides or skins
in the same for a time varying according to the strength of the solution from 1 to
48 hours. A small quantity of slacked lime may be added to the solution, but we
prefer to use the solution of sulphide of barium alone. If the hides or skins to be
treated are fresh market hides or skins, the time required for unhairing them is
much less than that required for dry or salted hides.
We find it advantageous to immerse the hides or skins, especially those of the
latter kind, first into liquors which have been already used, to bring about the
action of unhairing gradually, and to thoroughly soften them. For this operation
nothing will equal the old or used liquor in quick and beneficial action. Another
result of procceding in this manner is that the loosening of the scurf is effected very
advantageously, and the operation of "scudding" is facilitated. For this purpose
we pass the hides or skins from the oldest to the freshest pit. By the action of
rather strong solutions of sulphide of barium upon the hair, it is caused to come
off the hide in the form of a slimy gelatinous mass, whilst the pelt is not affected,
that is to say, it is not swelled as in the lime pits, and retains its natural suppleness.
For this reason the operation of "bateing " skins for dressing leather may be either
wholly or partly dispensed with.
In very much diluted solutions the hair is not destroyed, but the time required for
unhairing is much longer.
The solution of sulphide of barium we prepare by dissolving in water solid
sulphide of barium, produced by heating in a reverberatory furnace, or in closed
kilns in a temperature approaching a white heat, sulphate of baryta mixed with
carbonaceous matter.
To the solution of sulphide of barium, solutions of other sulphides, such as sulphides
of sodium or calcium, may be added.
For separating wool and hair from the pelt, without injuring or wetting the
latter, we use highly concentrated solutions of the sulphide of barium, and add
thereto any inert substance, such as plaster of Paris or clay, for the purpose of
producing a thin paste, which we apply by means of a mop or otherwise to the flesh
side only of the skin. The liquor penetrates the skin and loosens the hair or wool
on the other side, so that it can be removed dry and uninjured.
We also use for unhairing, instead of a solution of barium, a solution of sulphide
of sodium only, but prefer to do so without the addition of lime, which has an
injurious action on the pelt. We prepare the same, preferably, by decomposing a
solution of sulphate of soda by means of sulphide of barium. Although solutions
of sulphide of sodium can also be produced by heating to a red heat a mixture of
sulphate of soda and carbonaceous matter, and dissolving the resulting mass in
water; we prefer the former method, since in the latter process there would be a
considerable loss of materials, incomplete decomposition, and a destructive action on
the furnace or vessels wherein the heating is effected; and furthermore, the resulting
solution contains in solution considerable quantities of sulphide of iron, which stains
the hides.
We also produce a solution of sulphide of sodium, suitable for unhairing hides,
by treating alkali waste, after a few hours exposure to air, with cold, or preferably

page_text: with bot solutions of sulphate or carbonate of soda. We prefer sulphate of soda for
its comparative cheapness; the so-called nitre cake will answer our purpose.
Our Invention also comprises the further treatment of hides or skins, especially
when lime has been used for unhairing as in the ordinary process; the object of this
part of the said Invention is to dispense with the use of hen or pigeon dung in the
process of "bateing" for which we use solutions of chloride of magnesium and also
of chloride of calcium.
We have ascertained by analysis of water used in a tannery that it contains
notable quantities of the above salts, and for the purpose of our Invention we
reproduce the same artificially, that is to say, by the use of solutions of the aforesaid
salts, and thereby effect a result similar to that produced by the said "bateing"
process.
Having thus fully described our said Invention, and the manner of performing the
same, we wish it understood that we claim,-
First. In the treatment of hides or skins, the use of sulphide of barium, as above
described, and for the purpose specified.
Second. In the treatment of hides or skins, the use of solutions of sulphide of
sodium, prepared as above described, and for the purpose specified.
Third. In the treatment of hides or skins, the use of chloride of magnesium and
chloride of calcium, as above set forth for the purpose specified.
In witness whereof, I, the said Roger William Wallace, for myself and on
behalf of the said Carl Friedrich Claus, have hereunto set my hand and
seal, this Twenty-fourth day of January, in the year of our Lord One thousand
eight hundred and seventy-eight.
R. W. WALLACE. (L.S.)