A CERTAIN PROCESS OR PROCESSES FOR RECOVERING INDIGO FROM CERTAIN MATERIALS
Year: 1880

page_text: LETTERS PATENT to Frederick Albert Gatty, of Accrington, in the County
of Lancaster, Dyer and Calico Printer, for an Invention of "A CERTAIN
PROCESS OR PROCESSES FOR RECOVERING INDIGO FROM CERTAIN MATERIALS."
PROVISIONAL SPECIFICATION left by the said Frederick Albert Gatty at
the Office of the Commissioners of Patents on the 8th November 1880.
FREDERICK ALBERT GATTY, of Accrington, in the County of Lancaster, Dyer
and Calico Printer. "A CERTAIN PROCESS OR PROCESSES FOR RECOVERING
INDIGO FROM CERTAIN MATERIALS."
My Invention consists in treating woolen materials dyed with indigo with an
alkali, such as soda or potash, which dissolves the wool and sets the indigo at
liberty, which is then available for dyeing by the ordinary known processes in
practice for dyeing with indigo.
In order to attain my object I take a solution of caustic soda or potash at about
ten degrees of Twaddle's hydrometer, and place it in a suitable vessel, and put
woolen materials (rags of any description) containing indigo into it as long as they
will dissolve in it; to hasten the solution I heat the liquid.
When dissolved the alkali may be neutralized with an acid and the indigo
collected on a filter, or it may be deoxidized in the alkaline solution with any of
the known deoxidizing agents usually employed. Different degrees of strength of
the alkali does not affect the result, providing it is strong enough to dissolvo the
wool.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed by
the said Frederick Albert Gatty in the Great Seal Patent Office on the
6th May 1881.
FREDERICK ALBERT GATTY, of Accrington, in the County of Lancaster, Dyer
and Calico Printer. "A CERTAIN PROCESS OR PROCESSES FOR RECOVERING
INDIGO FROM CERTAIN MATERIALS."
My Invention consists in treating woollen materials dyed with indigo with an
alkali, such as soda or potash, which dissolves the wool and sets the indigo at
1

page_text: liberty, which is then available for dyeing by the ordinary known processes in
practice for dyeing with indigo.
In order to attain my object I take a solution of caustic soda or potash at about
ten degrees of Twaddle's hydrometer, and place it in a suitable vessel, and put
woollen materials (rags of any description) containing indigo into it as long as
they will dissolve in it; to hasten the solution I heat the liquid.
When dissolved the alkali may be neutralized with an acid, and the indigo
collected on a filter, or it may be deoxidized in the alkaline solution with any of
the known deoxidizing agents usually employed. Different degrees of strength of
the alkali does not affect the result, providing it is strong enough to dissolve the
wool.
And in order that my Invention may be fully understood and readily carried
into effect, I will describe how the same is to be performed.
I take by preference a solution of caustic soda at ten degrees of Twaddle's
hydrometer, and heat it in a suitable vessel to the boiling point; I then put
woollen materials (rags of any description) containing indigo into the solution as
long as it will dissolve them, continuing the boiling for about half an hour after
all the wool has been dissolved. I then let the liquid cool down to about ono
hundred and sixty degrees F., and add for every hundred gallons five pounds of
powdered zinc, or more if this quantity is not sufficient, to deoxidize the indigo
and give the liquid a golden yellow colour. In place of zinc other deoxidizing
agents well known to the indigo dyer, such as the salts of protoxide of iron or
tin, or certain sulphurets may be used. After the indigo is deoxidized the liquid
may be used at once for dyeing in the ordinary way, but I prefer to precipitate
the deoxidized liquid with an acid. I prefer to use muriatic acid of which I add
a sufficient quantity to render the liquid slightly acid. I then put the whole upon
a filter, and the precipitate can be kept in covered vessels until required for use.
In some cases in place of deoxidizing the indigo directly after the wool has been
dissolved I let the liquid get cold, and then neutralize it with an acid, for which
purpose I prefer to uso muriatic acid, and I then collect the precipitate on a filter,
which may be used as required in the ordinary way in which indigo is generally
used. When the woollen rags are dirty or contain foreign materials, I boil them
first with a weak solution of soda or potash or their carbonates, in order to cleanse
them and dissolve useless materials. After this operation they are dissolved and
treated as described.
Having stated the nature of my Invention and described how the same is to be
performed, I would have it understood that I do not restrict myself to any
particular proportions of the ingredients named, as they may be varied in strength
or quantity without materially altering the results, but what I do claim as my
Invention is,―
Recovering indigo from woollen materials containing the same by dissolving
them in an alkali, as herein described.
In witness whereof, I, the said Frederick Albert Gatty, have hereunto set my
hand and seal, this Fifth day of May, One thousand eight hundred and
F. A. GATTY. (L.S.)