Improvements in the Manufacture of Indigo.
Year: 1898

page_text: Date of Application, 8th Dec., 1898
Complete Specification Left, 6th Sept., 1899-Accepted, 14th Oct., 1899
PREDIVAAL DI MITICATION.
Improvements in the Manufacture of Indigo.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the Badische Anilin and Soda Fabrik, of
Ludwigshafen-on-Rhine, in the German Empire) to be as follows:-
My foreign correspondents have found that polyhydric alcohols of the fatty
series, and other polyhydroxy compounds which are closely related to them, and
also esters thereof, on melting together with anthranilic acid, or its salts, or
esters, under suitable conditions, yield leuco compounds of indigo.
The hydroxylic compounds of the fatty series which are especially suited for the
purposes of this invention are glycerine and its derivatives, such as alpha-chlor-
hydrin, epi-chlorhydrin, acetine, and also ordinary glycol, mannite, and various
kinds of starch and likewise cellulose and saw-dust. Instead of the free hydroxyl
compounds a similar result can be obtained when using the metallic compounds
thereof, such as calcium sodium or potassium glycerate. When the free hydroxy
derivatives are used, an alkali is added to the melt, but if the metallic salts be
used, the reaction will proceed without the addition of an alkali as such. The
alkalies, which are preferably used, are caustic potash and caustic soda, cither
singly, or in admixture with one another. Also these are used in admixture with
the alkaline earths, lime, or baryta, and the like. The leuco compound obtained
can be oxidised to indigo in the usual way; for instance, by treating the alkaline
solution of the melt with atmospheric air.
The following examples will serve to further illustrate the nature of the inven-
tion, but the invention is not confined to the examples. The parts are by
weight-
EXAMPLE 1:
PRODUCTION OF INDIGO FROM ANTHRANILIC ACID BY THE AID OF GLYCERINE IN
THE PRESENCE OF AN ALKALI:-
Mix one part of anthranilic acid, (or the corresponding quantity of a salt of
anthranilic acid) with two parts of glycerine, and four parts of caustic potash.
Heat the mixture rapidly to a temperature of about from 250 to 300 degrees
Centigrade. Maintain this temperature until the melt assumes a yellow-red to
brown-red colour. During the melting operation the melt becomes blown up
with bubbles. Allow the melt to cool, and dissolve it in water, and separate the
indigo in any well known or suitable way.
EXAMPLE 2.:--
PRODUCTION OF INDIGO FROM POTASSIUM SALT OF ANTHRANILIC ACID, BY THE AID
OF POTASSIUM GLYCERATE, AND NO FURTHER ALKALI:-
Mix together about one part of potassium salt of anthranilic acid and about
three parts of potassium glycerate, thoroughly dried. Heat this mixture to a
temperature of about 270 degrees Centigrade, until the generation of gas from the

page_text: PRODUCTION OF INDIGO FROM THE POTASSIUM SALT OF ANTHRANILIC ACID, BY THE
AID OF POTASSIUM GLYCERATE AND A MIXTURE OF CAUSTIC POTASH AND
LIME.
Mix together one part of the potassium salt of anthranilic acid, two parts of
potassium glycerate, two parts of caustic potash, and four parts of caustic lime,
and heat the mixture at a temperature of 270 to 290 degrees Centigrade, until
the mass is a light yellow colour. The reaction goes on quietly, without any
considerable bubbling up.
Allow the melt to cool, and dissolve it in water, pre-
venting as far as possible contact with air. Filter off from the lime and pass a
stream of air through the solution, until all the indigo is separated out.
Collect
and filter, wash with water, and then with hydrochloric acid, and, finally, with
water, and then dry.
In the foregoing examples epi-chlorhydrin, or acetine, can in each case be used
instead of the glycerol, and instead of the potassium salt of anthranilic acid the
equivalent quantity of the ethyl-ester of anthranilic acid can be used.
EXAMPLE 4:-
-
PRODUCTION OF INDIGO FROM ANTHRANILIC ACID BY MEANS OF ETHYLENE GLYCOL.
Mix together about three parts of the potassium salt of anthranilic acid, or the
same quantity of ethyl-ester of anthranilic acid, in about six parts of caustic
potash, and, to this mixture, add about two parts of ethylene-glycol. Mix the
mass thoroughly, and heat quickly to a temperature of about 300 degrees Centi-
grade which can be done, for instance, by inserting the vessel, containing the
mixed materials, into a hot metallic bath. When the evolution of gas has ceased,
and the melt has assumed a light yellow colour, the reaction may be regarded as
ended. Allow the melt to cool. Dissolve it in water, and precipitate and collect
the indigo in the well-known, or any suitable way.
EXAMPLE 5:-
PRODUCTION OF INDIGO FROM POTASSIUM SALT OF ANTHRANILIC ACID, BY THE AID
OF MANNITE.
Prepare a mixture of one part of mannite, one part of potassium salt of
anthranilic acid, and four parts caustic potash, and heat this mixture quickly,
to a temperature of from about 290 to 300 degrees Centigrade, whilst excluding
the air as far as possible. The mass bubbles up. Continue heating until the
colour of the melt has changed from brown-red to yellow-red and evolution of the
gas has ceased. Allow the melt to cool, dissolve it in water, and precipitate and
collect the indigo in the well-known, or any suitable way.
In this example, starch can be used instead of mannite; for instance, wheat
starch, or pure soluble starch, or cellulose can be used, for instance, in the form of
cotton wool, or in the form of the finest dried sawdust, and instead of the potassium
salt of anthranilic acid, the free acid can be used, or its ethyl ester.
The instances of the polyhydric alcohols and other polyhydric bodies of the fatty
series, and the derivatives thereof, hereinbefore mentioned, will serve to indicate
the wide range of bodies that can be used to produce indigo by means of anthranilic
acid, and its analogues herein defined, in accordance with this invention.
T 9th dow of December 1898
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C.,
Agents.

page_text: Improvements in the Manufacture of Indigo.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the Badische Anilin and Soda Fabrik, of
Ludwigshafen-on-Rhine, in the German Empire) and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement: -
My foreign correspondents have found that polyhydric alcohols of the fatty
series, and other polyhydroxy compounds which are closely related to them, and
also esters thereof, on melting together with anthranilic acid, or its salts, or
esters, under suitable conditions, yield leuco compounds of indigo.
The hydroxylic compounds of the fatty series which are especially suited for the
purposes of this invention are glycerine and its derivatives, such as alpha-chlor-
hydrin, epi-chlorhydrin, acetine, and also ordinary glycol, mannite, and various
kinds of starch and likewise cellulose and saw-dust. Instead of the free hydroxyl
compounds a similar result can be obtained when using the metallic compounds
thereof, such as calcium sodium or potassium glycerate. When the free hydroxy
derivatives are used, an alkali is added to the melt, but if the metallic salts be
used, the reaction will proceed without the addition of an alkali as such. The
alkalies, which are preferably used, are caustic potash and caustic soda, cither
singly, or in admixture with one another. Also they are used in admixture with
the alkaline earths; lime, or baryta, and the like. The leuco compound obtained
can be oxidised to indigo in the usual way; for instance, by treating the alkaline
solution of the melt with atmospheric air.
The following examples will serve to further illustrate the nature of the inven-
tion and the manner in which it can be carried into practical effect, but the
invention is not confined to the examples. The parts are by weight:-
EXAMPLE 1.
PRODUCTION OF INDIGO FROM ANTHRANILIC ACID BY THE AID OF GLYCERINE IN
THE PRESENCE OF AN ALKALI.
Mix one part of anthranilic acid, (or the corresponding quantity of a salt of
anthranilic acid) with two parts of glycerine, and four parts of caustic potash.
Heat the mixture rapidly to a temperature of about from 250 to 300 degress
Centigrade. Maintain this temperature until the melt assumes a yellow-red to
brown-red colour. During the melting operation the melt becomes blown up
with bubbles. Allow the melt to cool, and dissolve it in water, and separate the
indigo in any well known or suitable way.
EXAMPLE 2.
PRODUCTION OF INDIGO FROM POTASSIUM SALT OF ANTHRANILIC ACID, BY THE AID
OF POTASSIUM GLYCERATE AND NO FURTHER ALKALI.
Mix together about one part of potassium salt of anthranilic acid and about
three parts of potassium glycerate, thoroughly dried. Heat this mixture to a
temperature of about 270 degrees Centigrade, until the generation of gas from the
melt ceases, and the melt has assumed a yellow-red colour. Work up as described
in Example 1.
PRODUCTION OF INDIGO FROM POTASSIUM SALT OF ANTHRANILIC ACID, BY THE AID
OF POTASSIUM GLYCERATE AND NO FURTHER ALKALI.
Mix together about one part of potassium salt of anthranilic acid and about
three parts of potassium glycerate, thoroughly dried. Heat this mixture to a
temperature of about 270 degrees Centigrade, until the generation of gas from the
melt ceases, and the melt has assumed a yellow-red colour. Work up as described
in Example 1.

page_text: EILE C.
PRODUCTION OF INDIGO FROM THE POTASSIUM SALT OF ANTHRANILIC ACID, BY THE
AID OF POTASSIUM GLYCERATE AND A MIXTURE OF CAUSTIC POTASH AND
LIME.
Mix together one part of the potassium salt of anthranilic acid, two parts of
potassium glycerate, two parts of caustic potash, and four parts of caustic lime,
and heat the mixture at a temperature of 270 to 290 degrees Centigrade, until
the mass assumes a light yellow colour. The reaction goes on quietly, without any
considerable bubbling up.
Allow the melt to cool, and dissolve it in water, pre-
venting as far as possible contact with air. Filter off from the lime and pass a
stream of air through the solution, until all the indigo is separated out.
Collect
and filter, wash with water, and then with hydrochloric acid, and finally with
water, and then dry.
In the foregoing examples epi-chlorhydrin, or acetine, can in each case be used
instead of the glycerol, and, instead of the potassium salt of anthranilic acid the
equivalent quantity of the ethyl-ester of anthranilic acid can be used.
EXAMPLE 4.
PRODUCTION OF INDIGO FROM ANTHRANILIC ACID BY MEANS OF ETHYLENE GLYCOL
Mix together about three parts of the potassium salt of anthranilic acid, or the
same quantity of ethyl-ester of anthranilic acid, in about six parts of caustic
potash, and, to this mixture, add about two parts of ethylene-glycol. Mix the
mass thoroughly, and heat quickly to a temperature of about 300 degrees Centi-
grade which can be done, for instance, by placing the vessel, containing the
mixed materials, in a hot metallic bath. When the evolution of gas has. ceased,
and the melt has assumed a light yellow colour, the reaction may be regarded as
ended. Allow the melt to cool. Dissolve it in water, and precipitate and collect
the indigo in the well-known or any suitable way.
EXAMPLE 5.
PRODUCTION OF INDIGO FROM POTASSIUM SALT OF ANTHRANILIC ACID, BY THE AID
OF MANNITE.
Prepare a mixture of one part of mannite, one part of the potassium salt of
anthranilic acid, and four parts of caustic potash, and heat this mixture, quickly,
to a temperature of from about 290 to 300 degrees Centigrade, whilst excluding
the air as far as possible. The mass bubbles up. Continue heating until the
colour of the melt has changed from brown-red to yellow-red, and the evolution of
gas has ceased.
Allow the melt to cool, dissolve it in water, and precipitate and
collect the indigo in the well-known, or any suitable, way.
In this example, starch can be used instead of mannite; for instance, wheat
starch, or pure soluble starch; or cellulose can be used, for instance, in the form of
cotton wool, or in the form of the finest dried saw-dust and instead of the potassium
salt of anthranilic acid, the free acid can be used, or its ethyl ester.
The instances of polyhydric alcohols and other polyhydric bodies of the fatty
series, and the derivatives thereof hereinbefore mentioned, will serve to indicate
the wide range of bodies that can be used to produce indigo by means of anthranilic
acid, and its analogues herein defined, in accordance with this invention.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I claim is :-
1. In the manufacture of indigo, preparing indigo leuco compounds by melting
together a metallic hydroxyl compound herein before defined and anthranilic acid
or an analogue thereof also herein before defined.
2. In the manufacture of indigo, preparing indigo leuco compounds by melting
together a polyhydroxy alcohol, or other polyhydric body of the fatty series, or

page_text: derivative thereof, herein before defined; anthranilic acid, or an analogue thereof
also hereinbefore defined; and caustic alkali, with, or without, the addition of
an alkaline earth.
3. The manufacture of indigo leuco compound and indigo, substantially as
herein before described in the examples.
per 1899.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C.,
Agents.