IMPROVEMENTS IN THE EXTRACTING TANNIC ACID FROM LEATHER, AND IN PREPARING THE LEATHER FOR THE MANUFACTURE OF GLUE
Year: 1854

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of Glasgow, North Britain, Gentleman,
for the Invention of "IMPROVEMENTS IN THE EXTRACTING TANNIC ACID FROM
LEATHER, AND IN PREPARING THE LEATHER FOR THE MANUFACTURE OF GLUE."
-A communication from Obadiah Rich, of Cambridge, Massachusetts, in
the United States of America.
Sealed the 18th May 1855, and dated the 18th December 1854.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at
the Office of the Commissioners of Patents, with his Petition, on the
18th December 1854.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of Glasgow, North Britain, Gentleman, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN EXTRACTING TANNIC ACID
FROM LEATHER, AND IN PREPARING THE LEATHER FOR THE MANUFACTURE OF
GLUE," a communication from Obadiah Rich, of Cambridge, Massachusetts, in
the United States of America.
The object of this Invention is to procure tannine or tannic acid from scraps
or shavings, of leather, and to prepare the leather for the manufacture of glue,

page_text: It is well known that small pieces of leather & old boots and shoes are now
of little value. The tannic acid while combined with the gelatine of the skin is
worthless, and glue cannot be made from the tanned skin, as it is insoluble in
water; neither can the scraps of leather, although rich in fertilizing matter, be
used as a manure, as they are not readily decomposed by the action of heat
and moisture. In extracting the tanning or tannic acid from leather and con-
verting the same into its original condition, or what is termed raw hide, I
proceed as follows:-The leather, having been first chopped in small pieces, is
thoroughly washed to remove the dirt and a part of the coloring matter; it is
then placed in suitable cisterns or vats, and digested in a caustic alkali either
of ammonia, potash, or soda. The caustic soda is to be preferred, as it is much
the cheapest; its specific gravity should be about 1.025, and the leather should
remain in the solution from six to twelve hours, or until the whole of the
tannin has been extracted. The leather is then subjected to pressure to expel
as much of the liquor as possible, or it may be placed in the centrifugal
machine, which will produce nearly the same effect and leave the skin com-
paratively free from moisture; this liquor is now acidulated with sulphuric,
muriatic, or acetic acid, in order that the tannin may be set free and readily
combine with gelatine when used for tanning new skins; it may also be used
in dyeing, or other processes in which tanning is made use of. The principal
part of the tannic acid having been removed by the process above described, it
is necessary before proceeding to the manufacture of glue that the skin be
again subjected to the action of a new solution of the caustic soda or other
alkali, of about the same specific gravity as named above, in order to ensure
the entire removal of the tannin. This last solution after the skin is taken out
will be nearly as pure as at first, as it contains but a small amount of tanning,
and it is to be used for extracting the tanning from a second lot or charge of
leather. The tannic acid being now entirely removed, the scraps of skin are
to be well washed in pure water, to remove all traces of the soda. This being
accomplished, the scraps of leather are to be digested in dilute acid for about
twenty-four hours, in order to remove the coloring and earthy matters; when
this is done they are to be immersed in a weak solution of carbonate of soda,
for the purpose of neutralising any trace of acid that may remain, and when
well washed are then readily to be converted into glue by the usual process of
boiling and drying. The residuum after the gelatine is extracted may be used
It is very important that the tannic acid be entirely removed
from the skin, as herein described, for a very small portion of the tannin
remains in combination with the gelatine, the latter cannot be extracted by the
process of boiling. Old boots and shoes, and refuse leather of all kinds that is
as a manure.

page_text: not suitable for making a good quality of glue, may be subjected to the process
for the extraction of the tannin, and the whole of the skin, which is then readily
decomposed by air and moisture, used as a manure.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Seal Patent Office on
the 18th June 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
and of Glasgow, North Britain, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of December, in the year of our
Lord One thousand eight hundred and fifty-four, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Henry Johnson, Her special license that I, the said John Henry
Johnson, my executors, administrators, and assigns, or such others as I, the
said John Henry Johnson, my executors, administrators, or assigns, should at
any time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN THE EXTRACTING TANNIC ACID FROM LEATHER, AND IN PREPARING THE
LEATHER FOR THE MANUFACTURE OF GLUE," communicated from Obadiah Richi,
of Cambridge, Massachusetts, in the United States of America, upon the con-
dition (amongst others) that I, the said John Henry Johnson, by an instru-
ment in writing under my hand and seal, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, that is to say :-
The said Invention relates to the obtainment of tannin or tannic acid from
scraps or shavings of leather, and to the preparation of the leather for the

page_text: manufacture of glue. It is well known that small pieces of leather and old
boots and shoes are now of little value. The tannic acid while combined with the
gelatine of the skin is worthless, and glue cannot be made from the tanned
skin, as it is insoluble in water; neither can the scraps of leather, although rich
in fertilizing matter, be used as a manure, as they are not readily decomposed
by the action of heat and moisture. In extracting the tannin or tannic acid
from leather and converting the same into its original condition, or what is
termed raw hide, I proceed as follows: The leather having been first chopped
in small pieces, is thoroughly washed to remove the dirt and a part of the
coloring matters. It is then placed in suitable cisterns or vats and digested
in a caustic alkali either of ammonia, potash, or soda. The caustic soda is
to be preferred, as it is much the cheapest. Its specific gravity should be
about 1.025, and the leather should remain in the solution from six to twelve
hours, or until the whole of the tannin has been extracted. The leather is then
subjected to pressure, to expel as much of the liquor as possible, or it may be
placed in a centrifugal machine, which will produce nearly the same effect, and
leave the skin comparatively free from moisture. This liquor is now acidulated
with sulphuric, muriatic, or acetic acid, in order that the tannin may be set
free, and readily combine with gelatine when used for tanning new skins; it may
also be used in dyeing, or other processes in which tannin is employed. The
principle part of the tannic acid having been removed by the process above
described, it is necessary before proceeding to the manufacture of glue that the
skin be again subjected to the action of a new solution of the caustic soda or
other alkali, of about the same specific gravity as named above, in order to
ensure the entire removal of the tannin. This last solution, after the skin is
taken out, will be nearly as pure as at first, as it contains but a small amount
of tannin, and it is to be used for extracting the tannin from a second lot or
charge of leather. The tannic acid being now entirely removed, the scraps
of skin are to be well washed in pure water, to remove all traces of the
soda. This being accomplished, the scraps of leather are to be digested in
dilute acid for about 24 hours, in order to remove the coloring and earthy
matters; when this is done they are to be immersed in a weak solution of
carbonate of soda, for the purpose of neutralizing any trace of acid that
may remain, and when well washed are then ready to be converted into glue
by the usual process of boiling and drying. The residuum after the gelatine
is extracted may be used as a manure. It is very important that the tannic
acid be entirely removed from the skin, as herein described, for if a very small
portion of the tannin remains in combination with the gelatine, the latter
cannot be extracted by the process of boiling. Old boots and shoes, and

page_text: refuse leather of all kinds that is not suitable for making a good quality of
glue, may be subjected to the process for the extraction of the tannin, and the
whole of the skin, which is then readily decomposed by air and moisture, used
as a manure.
:
Although I have herein-before described this Invention as being applicable
to the extraction of tannin or tannic acid from scraps or shavings of leather
and 'old boots and shoes, it is nevertheless proposed to apply the same principle
for preparing and extracting tannic acid from the tannate of soda, the tannate
of potass, or other tannates, and combining it with such substance as will
render it suitable for transportation in a dry state, and fit for use in the arts of
dyeing and tanning, or for other purposes.
Tannic acid may be extracted from. oak, hemlock, and other kinds of bark,
nutgalls, and other substances, by subjecting them to the action of caustic soda
or other caustic alkalis until the alkali becomes neutral. To the tannate of
soda thus formed, a sufficient quantity of chloride of calcium is added to
combine with the tannin; by this process a double decomposition is effected;
chloride of sodium is formed in solution, while tannate of lime is precipitated.
This precipitate, after being separated by a filter, is to be washed until the
water is quite clear and then thoroughly dried. It is now in suitable order for
packing and transportation. To use this precipitate, water is acidulated with
sulphuric, oxalic, or other suitable acid, a proper quantity of tannate of lime is
then added to it, the sulphuric acid combines with the lime to form a sulphate
of lime, or if oxalic acid is used to form an oxalate of lime, while the tannin
becomes free in solution, and is then ready for the use of tanners or dyers.
If the acid employed to decompose the tannate of lime be in excess, it can
be neutralized by adding chalk or carbonate of barytes to the solution.
Any sulphate of lime in the solution can be precipitated with oxalic or other
acid or carbonate of barytes. As the action of the solution upon the gelatine
of the skin that is subject to it is very rapid, it is necessary that some extrac-
tive matter be used with it, as bran, sawdust, or spent bark; thus the tannate
of lime may be used for strengthening weak or spent vats. The ground bark
may thus be used for this purpose a great many times before it is removed
from the vat.
Having now described and particularly ascertained the nature of the said
5 Invention, and the manner in which the same is or may be used or carried
into effect, I would observe, in conclusion, that I do not confine or restrict
myself to the precise details or arrangements which I have had occasion
to describe or refer to, as many variations may be made therefrom without
deviating from the principles or main features of the said Invention; but

page_text: what I consider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent, is, the
process herein-before described for effecting the removal of tannic acid from
leather, and the subsequent preparation of the skin for manufacturing glue
or for use as a manure.
what I consider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent, is, the
process herein-before described for effecting the removal of tannic acid from
leather, and the subsequent preparation of the skin for manufacturing glue
or for use as a manure.
In witness whereof, I, the said John Henry Johnson, have hereunto
set my hand and seal, the Eighteenth day of June, One thousand eight
hundred and fifty-five.
J. HENRY JOHNSON. (L.S.)