Improvements in or connected with the Manufacture of Products and Colouring-matters related to the Indigo-group.
Year: 1898

page_text: Improvements in or connected with the Manufacture of Products
and Colouring-matters related to the Indigo-group.
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 & Soda Fabrik, of Ludwig-
shafen-on-Rhine, in the German Empire,) to be as follows:-
It is well known that indigo can be prepared by heating phenyl glycocoll, its
homologues and analogues, including phenyl glycocoll carboxylic acid, with a caustic
alkali, and oxidising the indoxylic leuco product obtained in a suitable way, as
described for example in the Specifications of Letters Patent Nos. 8726 and 10509,
both of 1890 and granted to me as communications from my foreign correspondents.
In these specifications it is repeatedly recommended to conduct the melt as far as
possible in the absence of air, as if unlimited access of air be permitted, charring or
burning of the materials is liable to take place.
The present invention consists firstly in a process for the production of isatinic
acid and isatin and analogues thereof, by alterations in the conditions in the melting
operations described, in such a way that a limited. quantity of air is present during
the reaction, secondly the indoxylic body may be suitably oxidised in a finished melt,
prepared whilst excluding air, or an indoxylic body may be taken either from such a
melt or from any other source and converted into the corresponding isatin body by a
suitable energetic oxidation. The invention thirdly consists in the production, by
the aid of these isatin compounds,, of indigo red colouring-matters or analogues
thereof...
In the product obtained by melting under treatment with air in the manner
mentioned, the isatin compounds are present in the form of isatinic acid or homologues
thereof. 90
To prepare isatin bodies from the finished. melt by energetic oxidation, a finished
melt containing one of the indoxylic bodies is, for instance, added to a mixture of
acetic and nitric acids, the nitric acid having the function of oxidizing, the acetic
acid being taken in such quantity as to acidify the melt and maintain the mixture
acid. But when preparing isatinic bodies in accordance with this part of the
invention, the indoxylic bodies can be used not merely in the melt but in an isolated
condition, whether obtained from the melt or from any other source, and they can be
oxidised either in acid or in alkaline or in neutral solution. Such reducing agents
however as ferric chloride solution and oxygen, for instance, in the form of air,
cannot be successfully used for this purpose, because they, being weak oxidising
agents, result in the formation of indigo. The following are instances of suitable
oxidising agents for use in this part of the invention.
(a) When oxidising in acid solution,-potassium bichromate, lead nitrate, mercuric
nitrate, and dilute nitric aci‹l.
(b) When oxidising in neutral solution-potassium permanganate, under conditions
when the solution is maintained neutral, for instance, by the addition of magnesium
sulphate

page_text: PREPARATION OF INDIGO-RED IN ALKALINE SOLUTION FROM THE MOTHER LIQUORS FROM
A MELT CONDUCTED IN THE PRESENCE OF AIR..
Take the mother-liquor obtained from seven hundred parts of phenyl-glycocoll-
ortho-carboxylic acid, sodium salt after treatment with alkali and air in the melting
operation, dissolving in water, oxidising, filtering off the indigo, all as described in
the foregoing example, and neutralise with sulphuric acid. Next dissolve twenty
parts of fresh indigo melt obtained as described in Example 1 in the neutral solution.
Neutralise again, and then make the liquid alkaline with carbonate of soda and boil,

page_text: After a short time the oxidation is concluded. Filter in order to separate from a
small quantity of pitchy matter. Add hydrochloric acid to the filtrate. A deep red.
crystalline precipitate of beta-naphtisatin is obtained. Collect by filtration and
work in the usual way.
OXIDATION OF INDOXYLIC ACID WITH POTASSIUM FERRICYANIDE AND THE CONVERSION
OF THE ISATIN INTO INDIGO-RED.
Dissolve about seven parts potassium ferricyanide in about two hundred parts of
boiling water and add about ten parts of caustic soda lye (containing about 35 per
cent. NaOH). To this solution add gradually nine parts of indoxylic acid. The
solution obtained contains the isatin. Acidify this with about fifty parts of acetic
acid, containing about 30 per cent. real acid, and then to this acid solution add about
nine parts of indoxylic acid or eight parts indoxyl in an aqueous solution. Filter the
solution whilst still hot, and add to the filtrate at a temperature of 30 degrees to 40
degrees Centigrade an excess of hydrochloric acid. The indigo-red begins to separate
out at once, and is soon completely separated.
In the above examples where idoxyl or indoxylic acid is mentioned the alkaline
melt containing these bodies can be used instead, making suitable allowance for the
presence of the alkali from the melt, and in Example 4 where the melt containing
indoxylic acid and indoxyl is mentioned, isolated indoxyl bodies can be used similarly,
and in that case it is unnecessary to add the acetic acid described.
The solution of isatin obtained in all the foregoing examples can if desired be used
at once for the production of indigo-reds by condensation with indoxyl bodies. When
it is desired to isolate the isatin compounds, it is advisable to work according to those
examples which yield solutions containing as little salt of any kind, such for instance
as the solutions obtained when using as an oxidising agent potassium permanganate,
copper sulphate, or manganese peroxide in alkaline solution.
Thated his orth to..
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.

page_text: Improvements in or connected with the Manufacture of Products
and Colouring-matters related to the Indigo-group.
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
communicated to me by The Badische Anilin & Soda Fabrik, of Ludwig-
shafen-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:
It is well known that indigo can be prepared by heating phenyl-glycocoll, its
homologues and analogues, including phenyl-glycocoll carboxylic acid, with a caustic
alkali, and oxidizing the indoxylic leuco product obtained in a suitable way, as
described for example in the Specifications of Letters Patent Nos. 8726 and 10509
both of 1890, and granted to me as communications from my foreign correspondents.
In these specifications it is repeatedly recommended to conduct the melt as far as
possible in the absence of air, as, if unlimited access of air be permitted, charring, or
burning, of the materials is liable to take place.
The present invention consists firstly in a process for the production of isatinic acid
and isatin and analogues thereof, by alterations in the conditions in the melting
operations described, in such a way that a limited quantity of air is present during
the reaction secondly, the indoxylic body in a finished melt may be suitably
oxidized, or an indoxylic body may be taken either from such a melt, or from any
other source, and converted into the corresponding isatin body by a suitable energetic
oxidation. The invention thirdly consists in the production by the aid of these isatin
compounds, of indigo-red colouring matters, or analogues thereof.
In the product obtained by melting, under treatment with air, in the manner
mentioned, the isatin compounds are present in the form of isatinic acid, or homo-
logues thereof.
To prepare isatin bodies from the finished melt by energetic oxidation, a finished
melt, containing one of the indoxylic bodies is, for instance, added to a mixture of
acetic and nitric acids, the nitric acid having the function of oxidizing, and the
acetic acid being taken in such quantity as to acidify the melt and maintain the
mixture acid. But, when preparing isatinic bodies in accordance with this part of
the invention, the indoxylic bodies can be used not merely in the melt but in an
isolated condition, whether obtained from the melt, or from any other source, and
they can be oxidized either in acid, or in alkaline, or in neutral, solution. Such
oxidising agents however as ferric chloride solution and oxygen, for instance in the
forin of air, cannot be successfully used for this purpose, because they, being weak
oxidising agents, result in the formation of indigo. The following are instances of
suitable oxidizing agents for use in this part of the invention.
(a) When oxidising in acid solution, potassium bichromate, lead nitrate, mercuric
nitrate, and dilute nitric acid.
(b) When oxidising in neutral solution, potassium permanganate, under conditions
when the solution is maintained neutral, for instance, by the addition of magnesium
sulphate.
(c) When oxidising in alkaline solution, ammonium persulphate, potassium
chronate, potassium permanganate, potassium ferri-cyanide, iodine, bromine,
chlorine; feric sulphate, cupric sulphate, and mercuric chloride precipitated with
caustic soda, lead superoxide, manganese peroxide.
The enumeration of these instances illustrates the wide range of oxidising agents
that can be employed, in carrying out this part of the invention. The initial
materials which have been successfully used are indoxyl and indoxylic acid, (or the

page_text: melts containing the same, or analogues thereof obtained in accordance with the
examples set forth in the before mentioned Specifications of Letters Patent 8726 and
10509, of 1890) ethyl-indoxyl, indoxylic ester, acetyl-indoxylic-ester, (see Berichte 14,
page 1742) para-methyl indoxylic-ester and naphindoxylic-ester. Instead of these
esters the corresponding-acids, or the alkaline melts thereof, can also be used.
To obtain the indigo-red colouring-matters, a melt, suitably prepared to contain the
isatin compounds, is dissolved in water, and the indigo leuco compounds, which are
simultaneously produced, are oxidized in the well-known way, to yield indigo, which
is filtered off and the mother-liquors so obtained, containing isatin compounds, are
condensed with indoxyl, or indoxylic acid, or their homologues, or a production of the
indigo-red compounds can be combined with the production of the isatin com-
pounds in accordance with the second part of this invention. For this purpose the
solution of the isatin compounds so obtained is condensed with indoxyl, or indoxylic
acid, or their analogues, whether in the solution of a melt, or obtained in any other
way.
The following examples will serve to further illustrate the nature of the invention
and the manner in which it can be performed, but the invention is not confined to
these examples The arts are hv weight_
Mix together about seven hundred parts of completely dry neutral phenyl-glycocoll-
ortho-carboxylic acid sodium salt, with one thousand four hundred parts of caustic soda,
freed from water as much as possible. The mixing should be effected in such a way
that a fine loose powder is obtained, containing air. Heat this mixture to
about 260°-270° Centigrade in such a way that the oxygen of the air contained in it
can take part in the reaction. Continue heating until the mass shews no further
increase in the intensity of the yellow, or orange, colour that it assumes, and then
allow it to cool. Dissolve the melt in water, pass a stream of air through to oxidise to
indigo the leuco compound produced, and filter from the indigo thus obtained.
nother-liquor contains the sodium salt of isatinic acid. My foreign correspondents
have found that it is liable to decomposition if boiled with strong alkaline liquids.
Concentrate the solution by evaporation at as low a temperature as possible preferably
in vacuo. The alkaline salt of the isatinic acid separates out, being with difficulty
soluble in caustic alkaline liquid. The salt obtained in this way can either be used
as such, or it can be converted in a known way into isatin itself.
The
In the above example instead of phenyl-glycocoll-ortho-carboxylic acid sodium salt
the free acid, or phenyl-glycocoll itself, or its homologues, or analogues, can be
employed and corresponding isatin compounds be obtained.
PREPARATION OF INDIGO-RED IN ALKALINE SOLUTION FROM THE MOTHER-LIQUORS FROM A
MELT PRODUCED IN THE PRESENCE OF AIR.
Take the mother-liquor obtained from seven hundred parts of phenyl-glycocoll-ortho-
carboxylic acid sodium salt, after treatment with alkali and air in the melting
operation, dissolving in water, oxidising, and filtering off the indigo, all as described
in the preceding example, and neutralise with sulphuric acid.
Next dissolve twenty parts of fresh indigo melt obtained as described in Example 1, in
the neutral solution. Neutralise again, and then make the liquid alkaline with carbonate
of soda, and boil. Indigo-red separates out, and the boiling is continued until no
further separation takes place.

page_text: OXIDATION OF BETA-NAPHTHINDOXYLIC-ETHYL-ESTER WITH POTASSIUM FERRICYANIDE
AND CAUSTIC SODA.
Dissolve about eight parts of potassium ferricyanide in about one hundred and sixty
parts of water and add about ten parts of caustic soda lye (containing about 35 per cent.
NaOH). Heat the solution to about 90 degrees Centigrade and add, gradually, about
two parts of beta-naphthindoxyl-ethyl-ester. Stir whilst adding, and subsequently.
After a short time the oxidation is concluded. Filter, in order to separate from a
small quantity of pitchy matter. Add hydrochloric acid to the filtrate. A deep red
crystalline precipitate of beta-naphtisatin is obtained. Collect by filtration and work
in the usual way.

page_text: Prepare a mixture of twenty parts of regenerated manganese per-oxide, thirty parts
of water and seven parts of caustic soda lye (containing about 20 per cent. NaOH).
Boil this mixture and add, slowly, an aqueous solution of eight parts of indoxyl. 5
When the oxidation is completed collect the isatin as described in the preceding
Example 5.
Dissolve about 4 parts of crystallised copper sulphate in sixteen parts of boiling
water, and precipitate by adding about three parts caustic soda lye (containing about
35 per cent. NaOH). Stir continually and add about one part of indoxylic acid. The
oxidation takes place almost instantaneously. Boil this mixture, and filter off the
precipitate of cuprous oxide and add an excess of hydrochloric acid to the filtrate.
The isatin will, in a short time, separate out in the crystalline form.
OXIDATION OF INDOXYLIC ACID WITH POTASSIUM FERRICYANIDE AND THE CONVERSION
OF THE ISATIN INTO INDIGO-RED.
Dissolve about seven parts potassium ferricyanide in about two hundred parts of
boiling water and add about ten parts of caustic soda lye (containing about 35 per
cent. NaOH). To this solution add, gradually, nine parts of indoxylic acid. The
solution obtained contains the isatin. Acidify this with about fifty parts of acetic
acid, containing about 30 per cent. real acid, and then, to this acid solution, add about
nine parts of indoxylic acid, or eight parts indoxyl, in an aqueous solution. Filter the
solution, whilst still hot, and add to the filtrate, at a temperature of 30 degrees to
40 degrees Centigrade, an excess of hydrochloric acid. The indigo-red begins to
separate out at once, and is soon completely separated.
In the above examples where indoxyl, or indoxylic acid; is mentioned the alkaline
melt containing these bodies can be used instead, making suitable allowance for the
presence of the alkali from the melt, and in Example 4, where the melt containing
indoxylic acid and indoxyl is mentioned, isolated indoxyl bodies can be used similarly,
and in that case it is unnecessary to add the acetic acid mentioned.
The solution of isatin obtained in all the foregoing examples can, if desired, be used
at once for the production of indigo-reds by condensation with indoxyl bodies. When
it is desired to isolate the insatin compounds it is advisable to work according to those
examples which yield solutions containing little salt of any kind, such for instance as
the solutions obtained when using, as an oxidising agent, potassium permanganate,
copper sulphate, or manganese peroxide in alkaline solution.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The manufacture of an isatinic body by melting a phenyl-glycocoll body with a
caustic alkali in the presence of a limited quantity of air; substantially as herein-
before described.
2. The manufacture of an isatinic body by the energetic oxidation of an indoxylic
body, substantially as herein before described.
3. The manufacture of indigo-red colouring-matters by preparing an isatinic body

page_text: according to either of the methods herein before described and claimed in the fore-
going first and second claiming clauses and condensing the said isatinic body with an
indoxyl body, substantially as herein before described.
4. The manufacture of isatinic bodies and of indigo-red colouring matters, substan-
tially as herein described in the examples.
J
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.