Improved Means for Preserving a Solution of Tannin and Keeping it from Fermenting or Changing into Gallic Acid.
Year: 1891

page_text: Date of Application, 6th June, 1891
Complete Specification Left, 22nd Feb., 1892-Accepted, 9th Apr., 1892
PROVISIONAL SPECIFICATION.
Improved Means for Preserving a Solution of Tannin and Keeping it
from Fermenting or Changing into Gallic Acid.
WILLIAM CROWTHER and JOHN CROWTHER, Mill Street Dye Works,
Dewsbury, in the County of York, Dyers, do hereby declare the nature of this
invention to be as follows:-
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We prevent the solution of tannin changing into gallic acid by reducing to, and
maintaining the temperature of the solution at or about 40° Fahrenheit, by which.
means the decomposition of the tannin is altogether arrested.
We effect this by employing the cold produced by any of the refrigerating
machines.
The method of conveying the cold from these machines usually employed, and
the one which we propose to adopt, is, by circulating brine from a refrigerating
machine through coils of pipes in the vessels, or tanks, containing the solution of
tannin, then back again to the machine to be recooled, th us keeping up a continuous
circulation and enabling us to keep the temperature of the tannin liquors under
control.
Dated this 4th dox of June 1801
WILLIAM CROWTHER.
JOHN CROWTHER.
COMPLETE SPECIFICATION.
Improved Means for Preserving a Solution of Tannin and Keeping it
from Fermenting or Changing into Gallic Acid.
We, WILLIAM CROWTHER and JOHN CROWTHER, Mill Street Dye Works,
Dewsbury, in the County of York, Dyers, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
We prevent the solution of tannin changing into gallic acid by reducing to, and
maintaining the temperature of the solution at or about 40° Fahrenheit, by which
means the decomposition of the tannin is altogether arrested.
We effect this by employing the cold produced by any of the refrigerating
machines.
The method of conveying the cold from the machines usually employed, and the
one which we propose to adopt, is by circulating brine from a refrigerating machine
through coils of pipes in the vessels or tanks containing the solution of tannin, then
back again to the machine to be recooled, thus keeping up a continuous circulation
and enabling us to keep the temperature of the tannin liquors under control.
Our said invention is applicable to any of the trades or manufactures where
solutions or decoctions of tannin materials are used, but more particularly for dyers
of cotton, and other vegetable fibres, or dyers of mixed goods, such as wool or
worsted and cotton, or other vegetable fibres; also it is equally well adapted for
the process of tanning leather.
Among the advantages derived from the use of our inv ention may be enumerated
the following:
:-
There is a considerable saving during the summer months especially in the
amount of tannin to be used, as by our method of treating the tannin solutions the
decomposition of the tannin is arrested, hence the solutions do not become sour or
change into gallic acid. Also in the dyeing of mixed goods when the temperature

page_text: of the tannin solutions is maintained at or about 40° Fahrenheit, the woollen
portion of the mixed goods does not absorb the tannin the same as it does when the
solutions are warmer, thus leaving the tannin to be absorbed by the cotton part of
the fabric, which cotton part is not so affected by the cold; likewise the affinity of
the tannin for the woollen portion of. mixed goods is not so great at a low
temperature, which is a further advantage, because, owing to the tannin not being.
absorbed by the woollen tissue, the succeeding operation of the cotton dyeing
process, which contains iron or other metallic compounds, does not in like manner
affect the woollen tissue so much, the goods being softer to the touch, and the
colors brighter and clearer in tone.
Further, in tan yards the adoption of our invention for preserving the contents
of the tanks, would effect a saving in time and extra labour, caused by the contents
of the tanks decomposing and becoming useless, through fermentation, and having
to be renewed from this cause, and also would prevent in the same degree the
nuisance and effluvia which are the evidence of spoilt tan liquors.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. Preserving solutions of tannin, and keeping such from turning sour or changing
into gallic acid, for the purposes set forth.
2. The method of and apparatus employed for preserving solutions of tannin and
keeping such from turning sour or changing into gallic acid, in the manner sub-
stantially as set forth.
Dated this 20th day of February 1892.
JOHN E. WALSH,
Royal Exchange, Leeds, Agent for the Applicants.