IMPROVED PROCESSES FOR THE TREATMENT OF HIDES & SKINS J
Year: 1882

page_text: LETTERS PATENT to William Maynard of New York, United States of America
and temporarily of Liverpool in the County of Lancashire for an Invention
of IMPROVED PROCESSES FOR THE TREATMENT OF HIDES & SKINS
J
PROVISIONAL SPECIFICATION left by the said William Maynard at the
Office of the Commissioners of Patents on the 7th October 1882.
WILLIAM, MAYNARD of New York, United States of America and temporarily of
Liverpool in the County of Lancashire "IMPROVED PROCESSES FOR THE TREATMENT
OF HIDES AND SKINS
"
This Invention relates to improvements in the operations of "soaking,"
'liming," and "tanning" hides and skins, and it consists essentially in the
employment of sulphurous acid in the manner and in the proportions, and in
certain of the operations in combination with the other substances, hereafter
specified.
In order to soften dry hides to the requisite extent without the possibility of
their becoming "pricked" (which is the technical name given by tanners to a
sort of decay produced by soaking hides in water) I prepare a bath or soak composed
of 1 part of water to 3 parts of sulphurous acid as produced in the apparatus for
the hydration of gases described in the specification of former Letters Patent dated
August 2nd 1876 N° 3094 which always produces a solution of sulphurous acid of a
certain specific gravity or uniform strength. I find that these are the just
proportions necessary to prevent any "pricking," to arrest decay, and to soften the
hides more effectually and quickly than is possible by water alone, or by any other
known means.
In the "liming" operation, I mix powdered sulphur with the quicklime before.
slaking it (or making it into what is technically known as a "lime") so that the
heat evolved in the hydration of this quicklime, will melt the sulphur and cause it
to combine with part of the lime and form sulphide of calcium, the presence of
which with the sulphurous acid (as produced in the aforesaid apparatus) renders
14

page_text: the lime more active. If potash be added the time required for liming can not
only bo shortened but the subsequent process of puring can be modified or dispensed
with at the option of the tanner, according to the proportions of the ingredients
used, and the manner of preparing them. Thus, if to every bushel of quicklime
1lb of sulphur be added before slaking and the "lime" (2.e. the lime bath in which
the hides are placed for the purpose of depilation) be made up with a liquid
composed of one half of a solution of sulphurous acid prepared in the apparatus
aforesaid, and one half water, then the hides will be ready for unhairing in one
third less time than by the usual method, and one third less "pure" (animal
excrement) will be required. If 2 ozs of caustic potash. be added to the "limo"
bath, its volume can be increased one fourth, and, the amount of " pure
correspondingly lessened.
"
12
Another method of carrying the process out is as follows:-One bushel of quick-
lime is mixed with 10 lbs of carbonate of potash, and 1lb of powdered sulphur,
and the whole are boiled in 25 gallons of water and 25 gallons of the before
mentioned solution of sulphurous acid; in this case the solution is allowed to settle
and the clear liquor removed from the carbonate of lime which deposits. The
hides treated with this solution will be depiled and the after operation of puring
may be dispensed with altogether. In either caso the goods after having been
washed with water, should be washed in a bath made of equal proportions of water
and the sulphurous acid solution hereinbefore referred to.
In the tanning operation I use a sulphurous acid in solution in admixture with
the tanning liquor in the proportions of 8 to 1 but I find that the goods should be
'uniforinly stained by the tanning material before the sulphurous acid is added. In
this way the goods will be tanned with less tanning material in less time and more
efficiently than by any known process.

page_text: 1
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Maynard in the Great Seal Patent Office on the 7th April
1883: 20
William MaynaRD of New York, United States of America, and temporarily, of
Liverpool in the County of Lancashire, IMPROVED PROCESSES FOR THE TREATMENT
OF HIDES AND SKINS"
- "
This Invention relates to improvements in the operations of "soaking,"
"liming," and "tanning" hides and skins, and it consists essentially in the
employment of sulphurous acid in the manner and in the proportions, and (in
certain of the operations) in combination with the other substances hereafter
specified.
"
In order to soften dry hides to the requisite extent without the possibility of
their becoming "pricked" (which is the technical name given by tanners to a sort of
decay produced by soaking hides in water) I prepare a bath or "soak" composed
of 1 part of water to 3 parts of sulphurous acid as produced in the apparatus for
the hydration of gases described in the specification of former Letters Patent dated
August 2nd 1876 N° 3094, which always produces a solution of sulphurous acid of
a certain specific gravity or uniform strength. The specific gravity of sulphurous
acid as produced in this apparatus under normal conditions of temperature and
pressure (20° C. and 760 m.m. bar) is about 1003° Beaumé. sp. gr. At higher
temperatures the volume absorbed would be less. 79-789 is the co-efficient of
absorption of sulphur di-oxide at 0° C. whilst the absorptiometric equilibrium
occurs at about 20° C for the same pressure.
I find that the proportions above mentioned are the just proportions to prevent
any "pricking," to arrest decay, and to soften the hides more effectually and
quickly than is possible by water alone or by any other known means, although
the amount used depends somewhat on the season of the year, more being required
in hot than in cold weather. The bath or soak is used at normal temperatures and
tlie goods remain therein until they are, in the judgment of the operator, soft
enough for "breaking," or for the "limes" when "breaking" is not a preparatory
operation.
In the "liming" operation, I mix powdered sulphur with the quicklime before
slaking it (or making it into what is technically known as a "lime") so that the
heat evolved in the hydration of this quicklime will melt the sulphur and cause it
to combine with part of the lime and form sulphide of calcium, the presence of
which with the sulphurous acid (as produced in the aforesaid apparatus) used in
making up the lime bath as hereafter mentioned, renders the "liming" operation
more effective. If potash be added the time required for "liming" cannot only be
sbortened but the subsequent process of "puring" can be modified or dispensed
with at the option of the tanner, according to the proportions of the ingredients
used and the manner of preparing them. Thus, if to every bushel of quicklime
1 lb of sulphur be added before slaking and the "lime" (i.e. the lime bath in which the
hides are placed for the purpose of depilation) be made up with a liquid composed
of one half of a solution of sulphurous acid prepared in the apparatus aforesaid,
and one half water, then the hides will be ready for unhairing in one-third less
time than by the usual method, and one-third less "pure" (animal excrement) will
be required. If 2 oz of caustic potash be added to the "lime" bath, its volume
can be increased one-fourth, and the amount of "pure" correspondingly lessened.
Another method of carrying the process out is as follows:-One bushel of
quicklime is mixed with 10 lbs of carbonate of potash, and 1 lb of powdered

page_text: sulphur, and the whole are boiled in 25 gallons of water and 25 gallons of the
before mentioned solution of sulphurous acid; in this case the solution is allowed
to settle and the clear liquor removed from the carbonate of lime which deposits.
The hides treated with this solution will be depiled and the after operation of
puring may be dispensed with altogether. In either case the goods after having
been washed with water, should be washed in a bath made of equal proportions of
water and the sulphurous acid solution heroinbefore referred to.
In the puring operation, when the amount of "puro" (animal excrement) is to
be lessened or dispensed with, I use the sulphurous acid solution in conjunction or
not with other adjuncts such as sugar, glucose, and chloride of ammonium
(sal ammoniac) N HCl.
In the tanning operation I use the sulphurous acid solution in admixture with.
the tanning liquor in the proportions of 8 to 1, but I find that the goods should be
quiformly stained by the tanning material before the sulphurous acid is added.
In this way the goods will be tanned with less tanning material in less time and
more efficiently than by any known process.
Having described the nature of the said Invention and the manner of performing
the same, I would observe that I claim the employment of sulphurous acid as new
in tanning in the exact manner and proportions, and with the other adjuncts
necessary to bring about the desired results, that is to say :-
1 In the process of softening dry hides and skins the employment of a bath or
"sonk" composed of sulphurous acid solution, substantially as herein specified.
2 In the process of "liming" hides and skius, and pieces of the same, the
employment in the lime bath of sulphurous acid solution, substantially of the
strength and in the proportions mentioned, in combination with sulphide of
calcium (with or without the addition of caustic potash) substantially as and for the
purpose specified.
3rd In the preparation of a lime bath for depilating bides and skins, the employ-
ment of a solution of sulphurous acid substantially of the strength and in the
proportion mentioned, in combination with a solution prepared by mixing together
and boiling in water, quicklime, carbonate of potash and sulphur, substantially as
and in the proportions hereinbefore specified.
4 The employment of sulphurous acid in the "puring" operation for the
purpose of curtailing or dispensing with the use of animal excrement.
5 In the process of tanning, the combination or admixture with the tanning.
liquor, of a solution of sulphurous acid substantially of the strength and in the
proportions and in the manner herein specified.
In Witness whereof I the said William Maynard have hereunto set my hand
and seal this fourth day of April, A.D. 1883.