A NEW AND USEFUL PROCESS FOR 'PURING' HIDES AND SKINS AND PIECES OF THE SAME
Year: 1881

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for an
Invention of "A NEW AND USEFUL PROCESS FOR 'PURING' HIDES AND
SKINS AND PIECES OF THE SAME." A communication from abroad by William
Maynard, of the City, County, and State of New York, United States of
America.
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 15th November 1881.
'
SYDNEY PITT, of Sutton, in the County of Surrey. "A NEW AND USEFUL
PROCESS FOR 'PURING HIDES AND SKINS AND PIECES OF THE SAME." A com-
munication from abroad by William Maynard, of the City, County, and State of
New York, United States of America.
The object of this Invention is to cleanse and purify hides and skins, or pieces of
the same, from lime and humus, and also to remove the epidermis when desirable,
and any hairs remaining from the depilation after liming, in a cheaper, safer, more
effective, and expeditious manner than has hitherto been known.
"
Accordingly in the practice of this Invention it has been discovered that a "soak
(described in the U.S. Letters Patent No. 136,082), which is a liquor composed of
water impregnated with sulphur dioxide, that has previously been employed in
soaking and softening the skins in preparing them for the liming operation, can be
utilized for the above purposes.
This results in a great saving of expense, and besides avoids the disagreeable odor
attendant upon the use of excrement of animals which is at present employed. The
said "soak," after the softened hides have been removed, contains sulphur,
phosphor, and carbon, with traces of nitrogen, in combination with hydrogen,
because in the soaking operation the skins have absorbed oxygen while the elements
above described have been eliminated from the skins and remain in the bath.
these in combination are efficient, and especially the phosphor and hydrogen in the
cleansing and "puring process."
""
All
It has been found that this solution sometimes lacks sufficient ammonia for the
purpose of cleansing rapidly, and also that the lime requires something with which

page_text: it can enter more rapidly into combination, and which will also render it soluble.
I therefore employ chloride of ammonia and sometimes sugar in small quantities,
while it has been found that argols assist the effect produced by the "soak," and
to be a very useful and in some cases necessary adjunct.
It has been found that the use of argols and chloride of ammonia singly or in
combination is non-effective without the soak, inasmuch as while the lime has been
eliminated the skin itself has not been left in that absolutely necessary state of
reduction and softness, technically known to tanners and readily distinguished by
them as "
pured."
This imperfect state or condition of the skin is obviated by the use of the "soak,"
either alone or in combination with small quantities of chloride of ammonia or
argols, or both.
It has been found that in "puring" the following can be more or less success-
fully used as substitutes for the chloride of ammonia and argols, viz., sugar,
hydrochloric acid, chloride of potassium, and casein, but the chloride of ammonia
and argols are preferable.
"
Instead of using the "soak" as above set forth, it is of course possible to
manufacture sulphuretted hydrogen or even the hydrogen compounds of carbon and
phosphor, but this expensive course need not be resorted to because the "soak” is
always at hand and available without cost after it has served its ordinary purpose
in the soaking operation. In the old process it has been necessary to employ
skilled labor during the operation of "puring," because of the tendency to
decomposition produced by the use of animal excrement, particularly of dogs. This
state of decomposition is designated by tanners generally as "running away," and
means what it implies, that the skins are frequently decomposed into a state of
liquid putridity. Skilled tanners by watching the vats can detect the approach
of such a condition, and hence they have to be employed. But there has heretofore
been no way devised in connection with the employment of excrement in "puring
to dispense with this class of skilled labor, because there is so much difference in
the strength of different kinds of excrement, and even so much difference in the
strength of that of the same kind, as that of dogs, for instance (due to the different
kinds of food upon which they have been fed, vegetables, bones, &c.), that practically
no definite period can be positively set within which it is safe to let the excrement
operate, but by the use of this Invention it is practicable to calculate by knowing
the strength of the "bate," which is easily and accurately obtained, the period of
time in which the " bating or puring can be safely and thoroughly performed.
This period will in practice vary somewhat, according to the nature of the skins
and the electrical condition of the atmosphere, but ordinarily it has been found
that in about one-fifth the usual time necessary where excrement is employed the
"puring" will be satisfactorily completed.
"
"
"
Different hides being of varying age and toughness are more or less sensitive to
the action of lime, therefore a greater or less quantity of lime has to be used, and
it necessarily follows that the "bate" also should be of variable degrees of
strength.
It has been found in practice that the strength of the liquid where chloride of
ammonia is used should vary from half a pound to one pound per hundred gallons
of the "soak," according to the thickness, age, and toughness of the hides and skins
to be treated. Although this rule is a guide it is not arbitrary, because much also
depends upon the number of skins to be treated in a given quantity of liquid.
But these facts or elements being all such as can be known by a competent
superintendent in advance, it is quite easy for him to calculate the short period of
time that will be required for the "puring" operation where this Invention is
practiced. It is to be understood that the liquid should be agitated from time to
time, and the skins moved in the same during this "puring" process.
By this Invention all the requirements are fulfilled at less expense and without
the disgusting odor, the danger of decomposition by the formation of too much
ammonia, or the action of phosphuretted gases upon the skins attendant upon the

page_text: use of excrement, while the removal of the lime is certain and the action upon the
epidermis perfect without the possibility of damage. Furthermore the chief agent
by which these desirable results are brought about is a product of the tannery
itself which has hitherto been deemed worthless.
Having thus described the Invention, what I claim and desire to secure by
Letters Patent is,-
"
The improved process of "puring" hides and skins, or pieces of the same,
substantially as described, which consists in immersing them in the "soak
described after it has been used for soaking, sometimes with the addition of a small
quantity of chloride of ammonia or argols, or both, or their equivalents, as set
forth.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Tenth day of November, in the year of our Lord One
thousand eight hundred and eighty one.
SYDNEY PITT. (L.S.)