The Manufacture or Production of Anthracene Compounds, and of Dye-stuffs Derived therefrom.
Year: 1896

page_text: Date of Application, 9th Apr., 1896
Complete Specification Left, 7th Jan., 1897-Accepted, 27th Feb., 1897
[Communicated from abroad by THE FARBENFABRIKEN, vormals FRIEDRICH
BAYER & Co., of Elberfeld, Germany.]
The Manufacture or Production of Anthracene Compounds, and of
Dye-stuffs Derived therefrom.
1 HENRY EDWARD NEWTON of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, do hereby declare the
nature of this invention to be as follows:-
My foreign correspondents have discovered that certain leuco derivatives of
hydroxyanthra-quinones may be used for the production of dye-stuffs, most
valuable products being obtained therefrom, and they have discovered new methods
for practically producing such leuco-compounds. Some years since Liebermann,
by acting on quinizarin with a mixture of hydroiodic acid and red phosphorus,
obtained a compound which he named "quinizarin hydruret" (see Liebig's
Annalen, vol. 212, page 14), and which belongs to the said class of leuco
hydroxyanthraquinones. My foreign correspondents have now discovered a new
and more profitable method of producing this "quinizarin hydruret," which method
is also applicable for the production of other leuco-compounds of hydroxyanthra-
quinones.
The new process for the production of quinizarin hydruret consists in the
reduction of purpurin. It is known that, by acting on purpurin with reducing
agents in alkaline solution, one hydroxylic group is readily substituted by a
hydrogen atom, xanthopurpurin being thus obtained. My foreign correspondents
have now found that, on carrying out the reduction of purpurin in weak alkaline,
or in neutral, or, more profitably, in acid solutions, not xanthopurpurin, but
quinizarin is formed, wherein the keto groups of the anthraquinone nucleus are
reduced by the influence of the reducing agents, so-called leuco derivatives
of quinizarin being obtained, which by oxidation are readily changed into
quinizarin.
In carrying out the herein-defined process of reducing hydroxyanthraquinones in
acid solution, my foreign correspondents employ, for instance, glacial acetic acid,
or concentrated sulphuric acid, and zinc powder, but there may be used also other
acids or other reducing agents, such as tin, aluminium, amalgam of aluminium,
chloruret of tin, or the like.
On treating purpurin with reducing agents in the manner herein before defined,
two different leuco derivatives of quinizarin are produced, which my foreign corre-
spondents term, for convenience, leuco quinizarin I" and "leuco quinizarin II."
The compound 11 is identical with the above named "quinizarin hydruret" first
produced by Liebermann, but the "leuco quinizarin I" has hitherto been unknown.
Leuco quinizario 1" is distinguished from "leuco quinizarin II" by its property
of being more readily changed by oxydizing agents into quinizarin; for instance,
a solution, in concentrated sulphuric acid, of "leuco quinizarin I" is slowly
oxydized, even at ordinary temperature, on heating at about from 70 to
90 degrees Centigrade. The oxidation takes place with great readiness; "leuco
quinizarin II" in concentrated sulphuric acid solution is oxidized only at a higher
temperature, viz., at about 120 to 130 degrees Centigrade.

page_text: My foreign correspondents give the following Examples I. and II., in order to
illustrate their new process of producing the leuco derivatives of quinizario in
glacial acetic acid solution. The parts are by weight.
EXAMPLE I.
THE PRODUCTION OF "LEUCO QUINIZARIN I."
A mixture prepared from 50 parts of dry purpurin, finely powdered, and about
from 250 to 400 parts of glacial acetic acid is heated at about from 70 to
80 degrees Centigrade, and about 25 parts of zinc powder are slowly introduced
into the mass during continual stirring. The reduction, which rapidly takes place,
is finished when the whole of the purpurin has dissolved, a solution of yellow
-colour being formed. The liquid thus obtained is filtered off from the unchanged
zinc powder, and the leuco compound is precipitated therefrom by the addition of
water. It is purified by means of a recrystallisation from acetone or the like.
The "leuco quinizarin 1" thus produced in a pure state forms gold-yellow leaves
soluble with readiness in hot acetone, alcohol, glacial acetic acid, and the like,
yielding yellow coloured solutions which possess bluish fluorescence. In cou-
centrated sulphuric acid solution, "leuco quinizarin I," owing to the oxidizing
action of sulphuric acid, is slowly changed into quinizarin, even at ordinary
temperatures, but the transformation proceeds with readiness on heating the
solution at about from 70 to 90 degrees Centigrade, sulphurous acid being evolved.
The solution of leuco quinizarin I in caustic soda-lye is likewise of yellow colour,
which by-and-by changes into violet, the leuco compound being. oxidized to
quinizarin.
EXAMPLE 1I.
THE PRODUCTION OF LEUCO QUINIZARIN II.
On employing, in the preceding Example 1, 50 parts of zinc powder in the place
of 25 parts used therein, and on containing the reduction until an isolated test
sample yields no quinizarin, when heated for a short time together with concentrated
sulphuric acid, at about from 80 to 90 degrees Centigrade, the "leuco quinizarin II"
herein before mentioned is produced, which is isolated in the manner described in
the preceding Example I. It may be purified by recrystallizing from aceton,
ligroine, or the like, being thus obtained in the form of long reddish-yellow needles
which possess the melting point 150 degrees Centigrade. On heating the compound
with concentrated sulphuric acid at about 130 degrees Centigrade, or at higher
temperatures, it is changed into quinizarin. Likewise quinizarin is formed on
allowing a caustic sodium solution of "leuco quinizarin II" to stand for some time
exposed to the action of the air, but this oxidation takes place more slowly than
that of a caustic sodium solution of "leuco quinizarin I."
As above mentioned, "leuco quinizarin II" is identical with the "quinizarin
hydruret" described by Liebermann.
The following example may serve to illustrate the process of reducing purpurin
in concentrated sulphuric acid solution. The parts are by weight.
EXAMPLE III.
THE REDUCTION OF PURPURIN BY MEANS OF
CONCENTRATED SULPHURIC
ACID AND ZINC POWDER.
About 20 parts of zinc powder are slowly stirred into a solution of 10 parts of
purpurin in about 200 parts of concentrated sulphuric acid cooled at about
from 10 to 5 degrees Centigrade, care being taken that the temperature does not
rise. When all the purpurin used in the process is reduced (which may be ascer-
tained by testing a sample), the mixture is poured into ice water, & yellow flakes

page_text: separate, which are filtered off, pressed, and dried. The product thus obtained
consists of a mixture of the two leuco quinizarins I and II herein before
defined.
EXAMPLE IV.
THE REDUCTION OF PURPURIN WITH ZINC POWDER IN NEUTRAL SOLUTION.
From 20 to 25 parts of zinc dust are introduced into a suspension of 10 parts of
purpurin in about 500 parts of water, and the mixture is heated to boiling under
stirring. When a test sample contains no purpurin, and dissolves in caustic soda
lye, or in concentrated sulphuric acid, with brownish-yellow colour, heating is
stopped, and the liquid is mixed with an excess of muriatic acid. The product
thus freed from zinc is filtered off, washed, and dried. It consists of a mixture of
"leuco quinizarin I" and "leuco quinizarin II."
Instead of a suspension in water of purpurin herein used, weak alkaline
solutions of purpurin may be used with the same result, for instance, solutions
prepared by means of the necessary quantities of sodium carbonate, or of sodium
borate, or the like, may be employed. Likewise, solutions of purpurin in watery
aluminium sulphate solution, or in alcohol, may be treated with zinc dust in the
manner described in the foregoing Example IV, mixtures of the leuco
quinizarins I and II being produced in either case.
My foreign correspondents have further found, that the herein before described
processes may be carried out also with other polyoxyanthraquinones, leuco
derivatives of hydroxyanthraquinones containing less hydroxy groups than
those used in the process being thus produced. On treating hexahydro-
xyanthraquinone, or alizarin hexacyanin with zinc dust in glacial acetic
acid, or in concentrated sulphuric acid solutions of leuco derivatives of alizarin
pentacyanin are formed, which, by oxidizing agents, are changed into
alizarin pentacyanin. On replacing, for instance, in the above Example I,
purpurin by an equivalent quantity of alizarin hexacyanin (or hexahydroxy
anthraquinone), a "leuco alizarin pentacyanin 1" is obtained, which, by con-
centrated sulphuric acid, is oxidized, even in cold, with readiness. Therefore, it
is isolated in pure form only with great difficulty. On treating alizarin hexa-
cyanin with a larger quantity of zinc dust in the manner described in the
Example 11 hereinbefore given, a "leuco alizarin pentacyanin II" is produced,
which likewise is oxidizable with readiness, but which can be isolated in pure
state. It crystallizes from glacial acetic acid in the form of brownish-yellow
leaves, or of flat needles, which dissolve in concentrated sulphuric acid with
brownish-yellow colour. Solutions of the compound in caustic soda-lye possess an
orange-yellow colour, which by the oxidizing action of air slowly changes
into blue.
My foreign correspondents have further found that purpurin sulphonic acid
(which is obtained by sulphonating purpurin, or by oxidizing the common alizarin
sulphonic acid), when treated with reducing agents in neutral or in acid solution
in the manner hereinfore defined, yields leuco derivatives of quinizarin sulphonic
acid.
The following example may serve to illustrate a process of practically producing
these leuco compounds. The parts are by weight.
EXAMPLE V.
THE PRODUCTION OF LEUCO DERIVATIVES OF QUINIZARIN SULPHONIC ACID.
10 parts of purpurin are sulphonated by heating the same together with about
1

page_text: ordinary temperature. A mixture of leuco compounds of quinizarin sulphonic
acid is thus obtained, which is isolated by salting out. On treating the new
product with oxidizing agents, either in alkaline or in acid solution, it is changed
into quinizarin sulphonic acid. On treating sulphonic acids of other polyhydroxy-
anthraquinones in an analogous manner, the corresponding leuco sulphonic acids
are produced.
The researches of my foreign correspondents have further shown, that on
treating alizarin bordeaux with reducing agents, either in alkaline or in acid
solution, a leuco derivative of alizarin bordeaux is produced, no hydroxylic group
being eliminated in this case, but only the keto groups of the anthraquinone
nucleus being reduced. My foreign correspondents give the following example,.
the parts being by weight.
EXAMPLE VI.
THE PRODUCTION OF LEUCO. ALIZARIN BORDEAUX.
50 parts of zinc dust are slowly introduced (with stirring) into a solution
prepared from 200 parts of a 20 per cent. alizarin bordeaux paste, 1800 parts of
water, 200 parts of caustic ammonia, and 65 parts of caustic soda-lye
(34 degrees Beaumé) heating the liquid at about from 70 to 80 degrees Centigrade.
When the solution assumes a pure yellow colour, which is changed but slowly by
the action of air, it is filtered off, and instantaneously mixed with about 400 parts
of a 33 per cent. muriatic acid diluted with water, the leuco compound being thus
separated in the form of yellow flakes. It is filtered off, pressed and dried. By
recrystallizing from glacial acetic acid (profitably with the addition of a small
quantity of zinc dust and water), the pure lenco alizarin bordeaux is obtained in
the form of little brownish-yellow crystals, which dissolve with readiness in the
usual organic solvents. The solution of the new compound in caustic soda-lye
possesses a brownish-yellow colour, which, under the oxidizing influence of air,
turns into violet, alizarin bordeaux being produced. On heating a concentrated
sulphuric acid solution of the leuco compound, likewise alizarin bordeaux is
formed.
The constitutional formula of the new body is probably either

page_text: derivatives of dye-stuffs are produced, which, by oxidizing agents, readily are
changed into the dye-stuffs themselves. Ordinarily, the leuco dye-stuffs formed
are oxidized, even during the process, by the action of the oxygen of the air;
therefore it is necessary to carry out the process in an atmosphere free from
oxygen, in order to obtain pure leuco dye-stuffs.
The condensation of the leuco hydroxyanthraquinones with amines, is hastened
by adding a suitable quantity of boric acid to the melt, and this may be carried
out at the low temperature of about from 80 to 100 degrees Centigrade. The
process in the manufacture of a leuco dye-stuff of the hereinbefore defined class
is illustrated by the following example, the parts being by weight.
EXAMPLE VII.
THE PRODUCTION OF A LEUCO DYE-STUFF FROM "LEUCO QUINIZARIN II."
A mixture prepared from 10 parts of "leuco quinizarin II" (see Example II),
100 parts of paratoluidine, and from 5 to 10 parts of boric acid, is heated at from
90 to 100 degrees Centigrade in a vessel, carbonic acid being introduced during
the operation. The finished melt is poured into dilute muriatic acid, and the leuco
dye-stuff thus precipitated is filtered off, washed, and, without drying, is
recrystallized by means of acetone. Thus, the leuco dye-stuff is produced in the
shape of rectangular Hat crystals which possess a brownish-yellow colour and
green fluorescence. It dissolves in the usual solvents with orange-yellow colour,
the solutions possessing green-yellow fluorescence. It dissolves with great readiness
in chloroform, from which it separates in crystalline form on the addition of
methyl alcohol. A solution of the leuco compound in concentrated sulphuric acid
is greenish-yellow, and does not possess a characteristic spectrum.
The leuco dyestuff has probably the following formula:-
Similar leuco compounds are produced by condensing "leuco quinizarin II"
with aromatic amines, instead of para toluidine, in the manner defined in the
preceding Example VII.
As above mentioned, the herein before described leuco dye-stuff from "leuco-
quinizarin II" and paratoluidine, is readily oxidised even by the oxygen of the
air. Thus, it yields a green dye-stuff, which is identical with that obtained on
melting quinizarin together with para-toluidine, in the presence of boric acid (see
the Specification of English Letters Patent No. 2392794).
In producing the said dye-stuff from the leuco compound, my foreign corre-
spondents employ all suitable oxydising agents, for instance, inanganese dioxide, or
the like, in the presence of glacial acetic acid, or of concentrated sulphuric acid.
The oxidation may also be carried out in alkaline solution; for example, a current
of air may be introduced into a solution of the leuco dye-stuff in alcoholic caustic
soda-lye, the dye-stuff being thus formed, and, as it is insoluble in alcohol, being
precipitated in the form of fine needles.
As above mentioned, the formation of the dye-stuff takes place even during the
process of melting together "leuco quinizarin II" and paratoluidine, in the

page_text: presence of air. My foreign correspondents have ascertained that in order to
produce practically the dye-stuff, an oxidising agent is profitably added to the
melt, and that quinizarin itself may he used best as oxidising agent, viz., on
melting a mixture of quinizarin and " leuco quinizarin II," together with para-
toluidine and boric acid, the said dye-stuff is formed with readiness, not only the
"leuco quinizarin II," but also the quinizarin used in the process, being readily
changed into the dye-stuff. Probably leuco dye-stuff is first formed in this process
by the interaction of leuco quinizarin and paratoluidine; this leuco dye-stuff is
changed into the dye-stuff itself by the oxydising action of the quinizarin, which
hereby is transformed into leuco quinizarin, capable of being condensed with a
corresponding quantity of paratoluidine. This process is repeated as long as
unchanged quinizarin is present; wherefore a large quantity of quinizarin may be
employed therein.
The following example is given in order to illustrate in what manner the dye-
stuff herein before mentioned may be practically produced. The parts are by
weight.
EXAMPLE VIII.
THE PRODUCTION OF A DYE-STUFF FROM LEUCO QUINIZARIN II AND
PARATOLUIDINE.
A mixture prepared from 10 parts of "leuco quinizarin II" (see the above
Example II), 20 parts of quinizarin, 300 parts of para-toluidine, and 20 parts of
boric acid, is heated, at from 110 to 120 degrees Centigrade, during several hours,
without the presence of air, until the melt contains no longer quinizarin. The
mass is then further heated in the presence of air, in order to oxydise a remainder
of leuco dye-stuff still contained therein.
The condensation may be carried out with a quantity of para-toluidine smaller
than that employed in the foregoing example, on using, in the process, an indifferent
solvent, such as alcohol, glacial acetic acid, or the like.
Instead of paratoluidine, other primary amines may be employed in the process
without altering the result.
In the place of the "leuco-quinizarin II," other leuco derivatives of hydroxy-
anthraquinones may be used in the processes defined in the foregoing Examples VII
and VIII; likewise leuco dye-stuffs or dye-stuffs respectively being obtained
similar to those produced from "leuco quinizarin II." My foreign correspondents,
for instance, employ leuco pentacyanin, leuco alizarin bordeaux, or the like
compounds, herein before described. In order to produce, for example, the dye-
stuff from leuco alizarin bordeaux by one operation, my foreign correspondents
proceed as follows:-
EXAMPLE IX.
THE PRODUCTION OF A DYE-STUFF FROM LEUCO ALIZARIN BORDEAUX AND
PARATOLUIDINE.
A mixture prepared from 10 parts of leuco alizarin bordeaux, 20 parts of alizarin
bordeaux, 300 parts of paratoluidine, and 20 parts of boric acid, are heated by
means of a water bath in the presence of air, until the melt has assumed a green
colour which no longer changes. The dye-stuff is isolated in the known manner
(viz. either by driving off the paratoluidine used in excess by means of steam, or
by withdrawing the same by extraction with dilute acids, and by drying the
insoluble part). It may be purified by recrystallisation from glacial acetic acid,
thus being obtained in the form of long needles.
The same dye-stuff may also be obtained on producing first the leuco dyestuff
from leuco alizarin bordeaux and paratoluidine, in the manner described in the
foregoing Example VII, and subsequently treating this compound with oxidising
agents.
.

page_text: The following table contains the main characteristics of some of the products
obtainable as hereinbefore defined.
The researches of my foreign correspondents shew that, on condensing leuco
derivatives of hydroxyanthraquinones with aromatic amines in the manner defined
in the above Example V11, first one hydroxylic group is substituted by au amine
radicle, and subsequently the other. For instance, by carefully melting together

page_text: leuco quinizarin II and para-toluidine, they have succeeded in obtaining a leuco
compound, which, when oxydised, yields the colouring matter which my foreign
correspondents have produced formerly from equal molecular proportions of
quinizarin and paratoluidine (see the Specification of English Letters Patent
No. 23927).
My foreign correspondents have further found, that the herein-described leuco
dye-stuffs may also be obtained in another manner, viz., on combining the process
of reducing the hydroxy-anthraquinones to leuco compounds, with that of con-
densing these leuco derivatives with amines. In order to produce leuco dyestuffs
in this manner, my foreign correspondents heat hydroxyanthraquinones, together
with an aromatic amine, in the presence of a suitable solvent (for instance, the
amines themselves may be used as solvents), adding a reducing agent and a
condensing agent to the melt at the same time. There may be used, as condensing
agent, boric acid, or substances capable of acting in the same or a similar manner.
As reducing agents, my foreign correspondents employ tin oxydule salts, or metals
such as zinc powder, iron filings, or the like, or all other materials in use for
reducing purposes. On using tic oxydule salts, it is not necessary to add a
condensing agent, the said salts acting not only as reducing, but also as condensing
agents. On carrying out the hereinbefore defined process in the presence of air,
the leuco compounds formed are oxidised even during the process, the corresponding
dye-stuff's being thus produced.
My foreign correspondents give the following examples, the parts being by
THE PRODUCTION OF THE LEUCO DYESTUFF DEFINED IN THE ABOVE
EXAMPLE VII FROM QUINIZARIN AND PARA-TOLUIDINE.
Into a melt prepared from 10 parts of quinizarin and 100 parts of para-toluidine,
at from 80 to 100 degrees Centigrade, 10 parts of chloruret of tin and 10 parts of
boric acid are introduced, and the mass is heated at the said temperature for from
3 to 4 hours in a vessel into which carbonic acid is introduced during the process.
The leuco compound thus produced is identical with that described in the
Example VII hereinbefore given. It is isolated in the known manner, riz., by
treating the melt with dilute acid, filtering off, and drying the insoluble part.
EXAMPLE XI.
THE PRODUCTION OF A LEUCO DYE-STUFF FROM ALIZARIN BORDEAUX AND
PARA-TOLUIDINE.
A mixture prepared from 10 parts of alizarin bordeaux, 5 parts of zinc dust,
10 parts of boric acid, 100 parts.of para-toluidine, and 20 parts of para-toluidine
hydrochloride, is heated at from 70 to 90 degrees Centigrade, during about from
2 to 3 hours, without the presence of air. The leuco dye-stuff thus obtained is
isolated in the well knowu manner; it is identical with that obtainable from leuco
alizarin bordeaux and para-toluidine in the manner hereinbefore defined.
In an analogous manner, from pentacyanin a leuco-dyestuff is obtained which is
identical with that obtainable froin pentacyanin and para toluidine.
On treating the herein defined leuco dye-stuffs with sulphonating agents,
sulphonic acids of these compounds are produced which, by oxidising agents, are
changed into sulphonic acids of the corresponding dyestuffs. My foreign corre-
spondents have described such sulphonic acids of dye stuffs in the Specification of
their English Letters Patent No. 23927%.
One method of practically producing sulphonic acids of the leuco dye-stuffs
hereinbefore defined, is illustrated by the following example, which is merely
typical. The parts are by weight.

page_text: THE SULPHONATION OF THE LEUCO DYESTUFF OBTAINED FROM LEUCO-
QUINIZARIN II AND PARA-TOLUIDINE.
10 parts of the leuco dyestuff obtained from "leuco quinizarin II" and para-
toluidine, in the manner described in the foregoing Example VII, are slowly stirred
into from 50 to 100 parts of fuming sulphuric acid (containing from 10 to 20 per cent.
SO), at ordinary temperature, care being taken that the temperature does not rise
during the operation. The mixture is then allowed to stand until a test sample
dissolves entirely in water, whereupon the mass is poured on ice. The greater
part of the sulphonic acid formed in the process thus precipitates, while another
part, which dissolves, is isolated by salting out.
The sulphonic acid thus produced dissolves in pure water with readiness,
yielding brownish-yellow solutions. Solutions in dilute alkalies first likewise shew
a brownish-yellow colour, which, by the action of the air, by and by changes into
green.
In order to obtain the corresponding dye-stuff from the sulphonated leuco dye-
stuff, the latter is treated with oxidising agents either in acid or in alkaline
solutions. My foreign correspondents employ in this process all the known
oxidising agents, such as peroxide of lead, manganse dioxide, or the like, or the
oxygen of the air.
For example, the mixture prepared by introducing 10 parts of the leuco dye-
stuff obtained from leucoquinizarin II and para toluidine, into from 50 to 100 parts
of fuming sulphuric acid, in the manner described in the preceding Example XII,
may be poured into about 2000 parts of ice water, and 10 parts of peroxide of
lead (in the form of a paste) may be introduced into the liquid under stirring.
A green solution is thus obtained, which is filtered off from the lead sulphate formed
during the process, and wherefrom the dye-stuff may be isolated by salting out.
The said dye-stuff may also be produced by introducing a current of air into a
solution in dilute alkali of the leuco sulphonic acid, heating the liquid to about
50 degrees Centigrade.
The researches of my foreign correspondents have shewn that, on heating at
about from 80 to 100 degrees Centigrade, for some time, the mixture obtained
from the leuco dyestuff and fuming sulphuric acid, in the manner defined in the
above Example XII, the leuco sulphonic acid first formed is readily changed into
the sulphonic acid of the dye-stuff, owing to the oxidising action of the con-
centrated sulphuric acid.
The sulphonation of the other leuco derivatives of dye-stuffs herein before
mentioned, such as those obtained from leuco quinizarin and other aromatic
amines, or from leuco-alizarin bordeaux, or leuco-pentacyanin, and aromatic amines
or the like, is carried out in an analogous manner, sulphonic acids of the said leuco
derivatives being thus produced, which, by oxidising in the above described
manner, are changed into sulphonic acids of the corresponding dyestuffs.
My foreign correspondents have found, that these sulphonic acids of leuco dye-
stuffs may be used, as such, for dyeing animal fibres, viz., on fixing the leuco
compounds on fibre in acid baths, and subsequently developing the dyestuffs by
a treatment with oxidising agents, such as potassium chromate or the like.
In carrying out the herein before defined processes, my foreign correspondents do
not limit themselves to the particulars given, as these may be varied without
altering the nature of this invention, which in general relates to the production of
leuco derivatives of hydroxyanthraquinones, or hydroxyanthraquinone sulphonic
acids, to the production of leuco dye-stuffs by condensing the said leuco hydroxy-
anthraquinones with aromatic amines, and to the production of the corresponding
dyestuffs from these leuco dyestuffs by oxidation. This invention further relates
to the manufacture of sulphonic acids of the said leuco dye-stuffs, and to the
B

page_text: manufacture of sulphonic acids of dye-stuffs by oxidising these leuco sulphonic
acids.
Dated this ath 2o. of Anul 1900
NEWTON & SON,
Agents for the Applicant.
The Manufacture or Production of Anthracene Compounds, and of
Dye-stuffs Derived therefrom.
I HENRY EDWARD NEWTON of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, 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 :-
My foreign correspondents have discovered that certain leuco derivatives of
hydroxyanthraquinones may be used for the production of dye-stuffs, and that
most valuable products may be obtained therefrom, and they have discovered new
methods for practically producing such leuco compounds. Some years ago, by
acting on quinizarin with a mixture of hydroiodic acid and red phosphorus, Lieber-
mann obtained a compound which he named "quinizarin hydride" (see Liebig's
Annalen, vol. 212, page 14), belonging to the said class of leucohydroxyanthra-
quinones. My foreign correspondents have now discovered a new and more
profitable method of producing this "quinizarin hydride," the which method is
also applicable to the production of other leuco compounds of hydroxyanthra-
quinones.
The new process for the production of quinizarin hydride consists in reducing
purpurin. It is known that, on acting on purpurin with reducing agents in an
alkaline solution, one hydroxy group is readily displaced by hydrogen, xantho-
purpurin being obtained. My foreign correspondents have now found, that if the
reduction of purpurin be effected in a weak alkaline or neutral, or, more profitably,
in an acid solution, a derivative of quinizarin is formed, instead of xanthopurpurin,
the keto groups of the anthraquinone nucleus being reduced, so-called leuco-
derivatives of quinizarin being formed, which are readily changed by oxidation
into quinizarin.
In carrying out the herein defined process of reducing hydroxyanthraquinones
in acid solutions, my foreign correspondents use, for instance, either glacial acetic
acid, or concentrated sulphuric acid and zinc powder, but other acids, or other
reducing agents, such as tin, aluminium, aluminium amalgam, stannous chloride, or
the like, may be used.
On treating purpurin with reducing agents in the manner hereinbefore defined,
two different leuco derivatives of quinizarin are produced, which my foreign
correspondents term, for convenience, "leucoquinizarin No. 1" and "leuco-
quinizarin No. II." The No. II compound is identical with the above named
quiuizarin bydride," first prepared by Liebermann, but the leuco quinizarin
No. I was hitherto unknown. Leuco quinizarin No. I is distinguished from leuco
quinizarin No. II by the greater readiness with which it is converted by oxidizing
agents into quinizarin; for instance, a solution of "leuco quinizarin No. 1" in
concentrated sulphuric acid is slowly oxidized, even at the ordinary temperature,
and, on heating the said solution at about 70 to 90 degrees Centigrade, the
oxidation takes place with great readiness, whilst a solution of "leuco-quinizarin
No. II in concentrated sulphuric acid, is oxidized only at a higher temperature,
viz., at about 120 to 130 degrees Centigrade.

page_text: THE PRODUCTION OF
LEUCOQUINIZARIN No. I."
A mixture of 50 parts of dry, finely powdered purpurin, and about 250 to
400 parts of glacial acetic acid, is maintained at about 70 to 80 degrees Centigrade,
and about 25 parts of zinc powder are slowly introduced into the mass, which is
continually stirred. The reduction rapidly takes place, and is finished when the
whole of the purpurin is dissolved, a yellow coloured solution being formed. The
liquid thus obtained is filtered from the unchanged zinc powder, and the leuco
compound is precipitated from the filtrate by the addition of water. It is purified
by recrystallisation from acetone or the like. The "lencoquinizarin No. 1" thus
produced, in a pure state forms golden yellow plates which dissolve readily in hot
acetone, alcohol, glacial acetic acid, and the like, forming yellow coloured solutions
which exhibit a bluish fluorescence. When dissolved in concentrated sulphuric
acid, owing to the oxidizing action exerted by the acid, "leucoquinizarin No. I"
is slowly changed into quinizarin, even at ordinary temperatures, and the trans-
formation proceeds with readiness on heating the solution to about 70 to 90 degrees
Centigrade, sulphurous acid being evolved. A solution of leuco quinizarin No. I in
caustic soda-lye is also of a yellow colour, which, however, gradually changes into
violet, the leuco compound being oxidized to quinizarin.
EXAMPLE II.
THE PRODUCTION OF "LEUCOQUINIZARIN No. II."
The "leuco quinizarin No. II" herein before mentioned is produced on using
50 parts of zine powder, instead of 25 parts, as prescribed in the preceding
Example I, and continuing the reduction until a test sample no longer yields
quinizarin, when heated for a short time with concentrated sulphuric acid at
about 80 to 90 degrees Centigrade. It is isolated in the manner described in the
preceding Example I. When purified by recrystallization from acetone, ligroine,
or the like, it is obtained in the form of long, reddish-yellow needles, which melt
at 150 degrees Centigrade. On heating the compound with concentrated sulphuric
acid at about 130 degrees Centigrade, or at higher temperatures, it is changed into
quinizarin. Quinizarin is also formed on allowing a solution of "leucoquinizarin
No. 11" in caustic soda, to stand for some time exposed to the air, but the
oxydation takes place more slowly than that of a similar solution of "leucoquinizarin
No. I."
As above mentioned, "leucoquinizarin No. II" is identical with the "quinizarin
hydride" described by Liebermann.
The following example may serve to illustrate the process of reducing purpurin,
when it is dissolved in concentrated sulphuric acid. The parts are by weight.

page_text: THE REDUCTION OF PURPURIN WITH ZINC POWDER IN NEUTRAL SOLUTION.
From 20 to 25 parts of zinc dust are added to 10 parts of purpurin suspended in
about 500 parts of water, and the mixture is heated to boiling, and continually
stirred. When a sample no longer contains purpurin, and dissolves in caustic soda-
lye, or in concentrated sulphuric acid, forming brownish-yellow coloured liquids
heating is stopped, and the liquid is mixed with an excess of muriatic acid. The
product thus freed from zinc is filtered off, washed, and dried. It consists of a
mixture of "leucoquinizarin No. I" and leuco quinizarin No. II."
Instead of suspending the purpurin in water, weak alkaline solutions may be
used, prepared by means of the necessary quantities of sodium carbonate, or of
sodium borate, or the like; or solutions of purpurin in a solution of aluminium
sulphate, or in alcohol, may be treated with zinc dust in the manner described in
the foregoing Example IV, mixtures of the leuco quinizarins Nos. I and II being
produced in either case.
My foreign correspondents have further found, that the hereinbefore described
processes may be carried out with all polyoxyanthraquinones containing hydroxy
groups in the 1. 2. 4, or "purpurin-position," leuco derivatives of hydroxy anthra
quinones containing fewer hydroxy groups than those used in the process being
thus produced. On treating a solution of hexahydroxyanthraquinone, or alizarin
hexacyanin, in glacial acetic acid, or concentrated sulphuric acid, with zinc dust,
leuco derivatives of alizurin pentacyanin are formed, which, on oxidation, yield
alizarin pentacyanin. Thus, on substituting, in the above Example I, for purpurin,
an equivalent quantity of alizarin hexacyanin (or hexahydroxy anthraquinone), a
"leuco alizarin pentacyania No. I" is obtained, which is oxidized with readiness
by even cold concentrated sulphuric acid, so that it is isolated in pure form only
with great difficulty. On treating alizarin hexacyanin (or betahydroxyanthra-
quinone) with a larger quantity of zinc dust in the manner described in the
Example II herein before given, a "leuco alizarin pentacyanin No. II" is produced,
which, although oxidized with readiness, can be isolated in a pure state.
crystallizes from glacial acetic acid in the form of brownish-yellow plates, or of
flat needles, which dissolve in concentrated sulphuric acid, affording a brownish-
yellow coloured liquid. Solutions of the compound in caustic soda-lye possess an
orange yellow colour, which is slowly changed into blue by the oxidizing action of
the air.
My foreign correspondents have further found, that purpurin sulphonic acid
(which is obtained by sulphonating purpurin, or by oxidizing ordinary alizarin
sulphonic acid), when treated with reducing agents in neutral or in acid solution, in
the manner hereinbefore defined, yields leuco derivatives of quinizarin sulphonic
acid.
The following example may serve to illustrate a process of practically producing
these leuco compounds. The parts are by weight.
THE PRODUCTION OF LEUCO DERIVATIVES OF QUINIZARIN SULPHONIC ACID.
10 parts of purpurin are sulphonated by heating them with about 20 parts of

page_text: fuming sulphuric acid (containing 20 per cent. SOa), at about 100 degrees Centigrade.
The mixture thus obtained is poured into from 500 to 1000 parts of water, and a
sufficient quantity of zinc dust is introduced into the liquid at the ordinary
temperature. A mixture of leuco compounds of quinizarin sulphonic acid is thus
obtained, which is isolated by salting out. On treating the new product with
oxidizing agents, either in alkaline or in acid solution, it is changed into quinizarin
sulphonic acid...
The researches of my foreign correspondents have further shewn, that on treating
lizarin bordeaux with reducing agents, either in alkaline or in acid solution, a
euco derivative of alizarin bordeaux is produced, no hydroxy group being
eliminated in this case, the keto groups of the anthra quinone nucleus alone being
reduced. My foreign correspondents give the following example, the parts
being by weight.
20 per cent. alizarin bordeaux paste, in 1800 parts of water, 200 parts of caustic
ammonia, and 65 parts of caustic soda-lye (34 degrees Baumé), heated to about
70 to 80 degrees Centigrade, and well stirred.
When the solution assumes a pure yellow colour, which is changed but slowly by
the action of the air, it is filtered off, and at once mixed with about 400 parts of
a 33 per cent. muriatic acid, diluted with water, whereupon the leuco compound
separates in the form of yellow flakes. It is filtered off, pressed, and dried. On
recrystallization from glacial acetic acid (to which a small quantity of zinc dust
and water may be added with advantage), the pure leuco alizarin bordeaux is
obtained in the form of small brownish-yellow crystals, which dissolve with
readiness in the usual organic solvents. The solution of the new compound in
caustic soda-lye is of a brownish-yellow colour, but, on exposure to the air, turns
violet, alizarinbordeaux being produced. Alizarin bordeaux is also formed on
heating a concentrated solution of the leuco compound in sulphuric acid.
The constitutional formula of the new compound is probably either
он он он
OH
or
OH OH
OH
0. OH
OH
CH
OH
O'H
The reduction of alizarin bordeaux may be carried out in acid or in neutral
solution, or other alkaline reducing agents, such as the sodium salt of stannous
oxide, or the like, may be used instead of that employed in the preceding
Example VI, without altering the result of the process, leuco alizarin bordeaux
being produced in every case.
Also, on treating alizarin pentacyanin in the manner hereinbefore defined, no
hydroxy group is eliminated, and only the keto groups of the anthraquinone nucleus
are reduced, leuco alizarin pentacyanin being obtained, which is also produced,
as herein before defined, on reducing alizarin hexacyanin, or hexahydroxy
anthraquinone..

page_text: My foreign correspondents have further discovered, that the leuco hydroxy-
anthraquinones herein before defined, are profitably used in the production of
dye-stuffs. On condensing the said leuco compounds with aromatic amines, leuco
derivatives of dye-stuffs are produced, which are readily converted into the
dye-stuffs by oxidizing agents. Ordinarily, the leuco dye-stuffs thus formed become
oxidized even during the process, by the action of the oxygen of the air, so that it
is necessary to carry out the process in an atmosphere free from oxygen, in order
to obtain pure leuco dye-stuffs.
The condensation of the leuco-hydroxyanthraquinones with amines, is hastened
by adding to the melt a suitable quantity of boric acid, or other appropriate
condensing agent, such as glacial acetic acid, muriatic acid, benzoic acid, or the
like, and may then be carried out at the low temperature of about from 80 to
100 degrees Centigrade.
The process of manufacturing a leuco dye-stuff of the hereinbefore defined class,
is illustrated by the following example, the parts being by weight.
ON OF
KUM
QUINIZARIN
A mixture of 10 parts of "leuco quinizarin No. II" (see Example II), 100 parts
of paratoluidine, and from 5 to 10 parts of boric acid, is heated at from 90 to
100 degrees Centigrade in a vessel from which the air is displaced by carbonic
acid. The finished melt is poured into dilute muriatic acid, and the leuco dye-stuff
which is precipitated, is filtered off and washed, and the moist precipitate is
recrystallized from acetone. The leuco dye-stuff is obtained in rectangular flat
crystals of a brownish-yellow colour, exhibiting a green fluorescence. It dissolves
in the usual solvents, forming orange-yellow coloured solutions, which exhibit a
green yellow fluorescence. It dissolves with great readiness in chloroform,
from which it separates in a crystalline form on the addition of methylalkohol. A
solution of the leuco compound in concentrated sulphuric acid is of a greenish-
yellow colour, and does not possess a characteristic spectrum.
Similar leuco compounds are produced by condensing "leuco quinizarin No. II
with other aromatic amines, instead of para-toluidine, in the manner defined in the
preceding Example VII.
As above mentioned, the herein before described leuco-dyestuff from "leuco-
quinizarin No. 11" and para-toluidine, is readily oxydised, even by the oxygen of
the air, yielding a green dye-stuff which is identical with that obtained on melting
quinizarin together with paratoluidine in the presence of boric acid (see the
Specification of English Letters Patent No. 23927").
In producing the said dye-stuff from the leuco compound, my foreign
correspondents employ all suitable oxydising agents, for instance, manganese
dioxide, or the like, in the presence of glacial acetic acid, or of concentrated
sulphuric acid. The oxidation may also be carried out in alkaline solution,
for example, a current of air may be introduced into a solution of the leuco
dye-stuff in alcoholic caustic soda-lye; the dye-stuff which is formed, being
insoluble in alcohol, is precipitated in the form of fine needles.
As above mentioned, the formation of the dye-stuff takes place, even during the
process of melting together "leucoquinizarin No. II and paratoluidine in the
presence of air. My foreign correspondents have ascertained that it is
advantageous, in producing the dye-stuff, to add an oxidising agent to the melt,
and that quinizarin itself may be best used as oxidising agent. Thus, on melting
a mixture of quinizarin and leucoquinizarin No. II" with paratoluidine and boric
acid, the said dye-stuff is formed with readiness, not only the "leucoquinizarin
No. II," but also the quinizarin used in the process, being readily changed into

page_text: the dye-stuff. Probably a leuco dye-stuff is first formed in this process by the
interaction of leuco quinizarin and paratoluidine; this leuco dyestuff is changed
into the dye-stuff itself by the oxidising action of the quinizarin, which is at the
same time transformed into leuco-quinizarin, capable of being condensed with a
corresponding quantity of paratoluidine, and, as this process is repeated as long as
unchanged quinizarin is present, a relatively large quantity of quinizarin may be
employed.
The following example is given in order to illustrate in what manner the
dye-stuff hereinbefore mentioned may be practically produced. The parts are by
weight
THE PRODUCTION OF A DYE-STUFF FORM "LEUCO QUINIZARIN No. II" AND
PARA-TOLUIDINE.
A mixture of 10 parts of "leuco-quinizarin No. II" (see the above Example II),
20 parts of quinizarin, 300 parts of paratoluidine, and 20 parts of boric acid, is
heated, at from 110 to 130 degrees Centigrade, during several hours, air being
excluded until the melt no longer contains quinizarin. The mass is then, further
heated in the presence of air, in order to oxidise the residue of leuco dye-stuff still
contained therein.
The condensation may be carried out with a quantity of paratoluidine smaller
than that employed in the foregoing example, by using, in the process, an
indifferent solvent, such as alcohol, glacial acetic acid, or the like.
Instead of paratoluidine, other primary amines may be employed in the process,
without altering the result.
In the place of "leuco-quinizarin No. II," other leuco-derivatives of hydroxy-
anthraquinones may be used in the processes defined in the foregoing Examples VII
and VIII, in which cases, leuco dye-stuffs, or dye-stuffs, are obtained, similar to
those produced from "leuco quinizarin No. II." My foreign correspondents, for
instance, employ leuco-pentacyanin, leuco-alizarin bordeaux, or the like compounds,
hereinbefore described."
In order to produce, for example, the dye-stuff from leuco alizarin bordeaux in
one operation, my foreign correspondents proceed as follows:
THE PRODUCTION OF A DYE-STUFF FROM LEUCO ALIZARIN BORDEAUX AND
PARATOLUIDINE.
A mixture of 10 parts of leuco-alizarin bordeaux, 20 parts of alizarin bordeaux,
300 parts of paratoluidine, and 20 parts of boric acid, are heated by means of a
water-bath in the presence of air, until the melt has assumed a green colour, which
no longer changes. The dye-stuff is isolated in the known manner (viz., either by
removing the paratoluidine used in excess by means of steam, or by extraction with
dilute acids, and then drying the insoluble part). It may be purified by recrystal-
lisation from glacial acetic acid, and is then obtained in the form of long needles.
The same dye-stuff may also be obtained by first preparing the leuco dye-stuff
from leuco-alizarin bordeaux and para toluidine in the manner described in the
foregoing Example 11, and subsequently treating this compound with oxidising
agents.

page_text: In the following table are summarized the properties characteristic of several of
the pure products obtainable as herein before defined:
molecular proportion of leuco
quinizarin No. II, and 2 molecular
proportions of alphanaphthyl-
amine
molecular proportion of leuco
alizarin bordeaux, and 2 molecular
proportions of aniline
molecular proportion of leuco
alizarin bordeaux and 2 molecular
proportions of paratoluidine
molecular proportion of leuco
alizarin bordeaux, and 2 molecular
proportions of alphanaphthyl-
amine
The researches of my foreign correspondents shew that, on condensing leuco
derivatives of hydroxyanthraquinones with aromatic amines in the manner defined
in the above Example VII, first one, and then the other, hydroxy group is displaced
by an amine radicle. For instance, by carefully melting together leuco-quinizarin 1

page_text: No. II and paratoluidine, they have succeeded in obtaining a leuco compound
which, when oxidised, yields the colouring matter formerly produced by my foreign
correspondents from equal molecular proportions of quinizarin and paratoluidine
(see the Specification of English Letters Patent No. 23927).
My foreign correspondents have further found that the herein described leuco
dye-stuffs may also be obtained in another manner, viz., by combining the process
of reducing the hydroxyanthraquinones to leuco compounds, with that of condensing
these leuco derivatives with amines.
In order to produce leuco dye-stuffs in this manner, my foreign correspondents
heat hydroxyanthraquinones, together with an aromatic amine, in the presence of a
suitable solvent (or the amines themselves may be used as solvents), at the same
time adding a reducing agent and a condensing agent to the melt. Boric acid, or
substances capable of acting in the same or a similar manner, may be used as
condensing agents. As reducing agents, my foreign correspondents employ
stannous salts, or metals such as zinc powder, iron filings, or the like, or all other
materials in use for reducing purposes. On using. stannous salts, it is not necessary
to add a condensing agent, the said salts acting not only as reducing. but also as
condensing agents.
On carrying out the hereinbefore defined process in the
presence of air, the leuco compounds which are formel are oxidisel during the
process, the corresponding dye-stuffs being produce1.
My foreign correspondents give the following examples, the parts being by
THE PRODUCTION OF THE LEUCO DYESTUFF DEFINED IN THE ABOVE
EXAMPLE VII FROM QUINIZARIN AND PARA-TOLUIDINE.
10 parts of quinizarin having been dissolved in 100 parts of paratoluidine, heated to
from 80 to 100 degrees Centigrade, 10 parts of stannous chloride and 10 parts of boric
acid are introduced, and the mixture is maintained at the said temperature during
3 to 4 hours, in a vessel into which carbonic acid is introduced during the process.
The leuco compound thus preduced is identical with that described in the
Example VII herein before given. It is isolated in the known mauner, viz., hy
treating the melt with dilute acid, filtering off, and drying the insoluble part.
THE PRODUCTION OF A LEUCO DYE-STUFF FROM ALIZARIN BORDEAUX AND
PARATOLUIDINE.
A mixture of 10 parts of alizarin bordeaux, 5 parts of zinc dust, 10 parts of
boric acid, 100 parts of para-toluidine. and 20 parts of paratoluidine hydrochloride,
is heated at from 70 to 90 degrees Centigrade during about 2 to 3 hours, air being
carefully excluded. The leuco dye-stuff thus obtained is isolated in the known
manner. It is identical with that obtained from leuco alizarin bordeaux and para-
toluidine, in the manner herein before defined.
In an analogous manner, a leuco dye-stuff is obtained from pentacyanin, which
is identical with that obtainable from pentacyanin and para-toluidine.
On treating the herein-lefined leuco dye-stuff's with sulphonating agents,
sulphonic acids of these compounds are produced, which are converted by oxidising
agents into sulphonic acids of the corresponding dye-stuffs. My foreign corre-
spondents have described such sulphonic acids of dye-stuffs in the Specification of
their English Letters Patent No. 23927%.
One method of practically producingi sulphonic acids of the leuco dye-stuffs
с

page_text: THE SULPHONATION OF THE LEUCO DYE-STUFF OBTAINED FROM "LEUCO-
QUINIZARIN No. II" AND PARATOLUIDINE.
10 parts of the leuco dye-stuff obtained from "leuco quinizarin No. II" and
para-toluidine, in the manner described in the foregoing Example VII, are slowly
stirred into from 50 to 100 parts of fuming sulphuric acid (containing from 10 to
20 per cent. SO3), at the ordinary temperature, care being taken that the
temperature does not rise during the operation. The mixture is then allowed to
stand until a sample dissolves entirely in water, whereupon the mass is poured outo
ice. The sulphonic acid is isolated by salting out.
The sulphonic acid thus produced dissolves with readiness in water, yielding
brownish-yellow solutions. Solutions in dilute alkalies at first are also of a
brownish-yellow colour, but, by the action of the air, this gradually changes into
green.
In order to obtain the corresponding dye-stuff from the sulphonated leuco dye-
stuff, the latter is treated with oxidising agents, either in acid or in alkaline
solution. My foreign correspondents employ in this process all the known
oxidising agents, such as peroxide of lead, manganese dioxide, or the like, or the
oxygen of the air.
For example, the mixture prepared by introducing 10 parts of the leuco dye-
stuff obtained from "leuco quinizarin No. II" and para-toluidine, into from 50 to
100 parts of fuming sulphuric acid, in the manner described in the preceding
Example XII, may be poured into about 2000 parts of ice water, and 10 parts of
peroxide of lead (in the form of a paste) may be stirred into the liquid. A green
solution is thus obtained which is filtered off from the lead sulphate, and the dye-
stuff may be then isolated by salting out.
The said dye stuff may also be produced by introducing a current of air into a
solution, in dilute alkali, of the leuco sulphonic acid, heating the liquid to about
50 degrees Centigrade.
The researches of my foreign correspondents have shewn that, on heating for
some time, at about 80 to 100 degrees Centigrade, the mixture obtained from the
leuco dye-stuff and fuming sulphuric acid in the manner defined in the above
Example XII., the leuco sulphonic acid first formed is readily changed into the
sulphonic acid of the dye-stuff, owing to the oxidising action exerted by concentrated
sulphuric acid.
The sulphonation of the other leuco derivatives of dye stuffs herein before
mentioned, such as those obtained from leuco-quinizarin and other aromatic amines,
or from leuco-alizarin bordeaux, or leuco-pentacyanin and aromatic amines or the
like, is carried out in an analogous manner, sulphonic acids of the said leuco
derivatives being thus produced, which are converted by oxidation, in the above
described manner, into sulphonic acids of the corresponding dye-stuffs.
My foreign correspondents have found that these sulphonic acids of leuco dye-
stuffs may be used, as such, for dyeing animal fibres, viz., by fixing the leuco
compounds on the fibre in acid baths, and subsequently developing the dye-stuffs
by a treatment with oxidising agents, such as potassium chromate or the like.
In carrying out the herein before defined processes, my foreign correspondents do
not limit themselves to the particulars given, as these may be varied without
altering the nature of this invention, which, speaking generally, relates to the
production of leuco derivatives of hydroxyanthraquinones or hydroxy anthraquinone
sulphonic acids, to the production of leuco dye-stuffs, by condensing the said leuco

page_text: hydroxyanthraquinones with aromatic amines, and to the production of the corre-
sponding dye-stuffs from these leuco dye-stuffs by oxidation. This invention
further relates to the manufacture of sulphonic acids of the said leuco dye-stuffs,
and to the manufacture of sulphonic acids of dye-stuffs by oxidising thesé leuco
sulphonic acids.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed (as communicated to me
from abroad), I declare that what I claim is :-
1. The process for producing leuco derivatives of hydroxyanthraquinones
containing the hydroxy-groups in the so called quinizarin position, which process
consists in reducing hydroxyanthraquinones containing the hydroxy groups in the
so-called purpurin position (OH OH OH = 1.2.4), such as purpurin,.
hexaoxyanthraquinone, alizarin hexacyanin, and the like, or sulpho acids thereof,
in acid, neutral, or weak alkaline solution.
2. The production of leuco derivatives of alizarin pentacyanin and alizarin
bordeaux, by reducing these hydroxyanthraquinones.
3. The manufacture of leuco derivatives of dye-stuffs of the anthracene series
containing nitrogen, by condensing a single molecular proportion of one of the leuco.
hydroxyanthraquinones, and sulpho acids thereof, obtained by the processes
defined in the Claims 1 and 2, either with one or with two molecular proportions of
any primary aromatic amine, in an atmosphere free from oxygen, with or without
the assistance of condensing agents.
4. The process for producing leuco dye-stuffs of the anthracene series, con-
taining nitrogen, in one operation, which process consists in carrying out, in one
operation, the transformation of quinizarin and of the bydroxy-anthraquinones
referred to in the Claim 2, into their corresponding leuco compounds, and the
condensation of the latter with amines.
5. In the process defined in the foregoing Claims 1, 2, and 4, the use of stannous
chloride, zinc powder, iron, aluminium, or similar reducing agents acting in the
same manner.
6. The manufacture of sulpho-acids of the leuco dye-stuffs obtainable by the-
processes defined in the foregoing Claims 3 and 4, by treating the said leuco dye-
stuffs with sulphonating agents.
7. The transformation of the leuco compounds containing nitrogen, and the
sulpho acids thereof, described in the foregoing Claims 3, 4, and 6, into dye--
stuffs, by a treatment with oxidising agents.
8. In the process defined in the preceding Claim 7, the oxidation of the leuco
compounds by means of manganese dioxide, lead dioxide, mercuric oxide, or
similar oxidising agents acting in the same manner in the presence of glacial acetic
acid, or of concentrated sulphuric acid or the like, or by the introduction of
oxygen, or of mixtures containing oxygen, such as air, into alkaline solutions of
the leuco compounds.
9. The process of producing dye-stuffs from leuco bydroxyanthraquinones in
one operation, viz., by melting the said leuco compounds, together with primary
aromatic amines, in the presence of oxidising agents, with or without the assistance
of condensing agents, such as boric acid.
10. In the process described in the foregoing Claim 9, on the one hand, the use-
of the leuco-hydroxyanthraquinones described in the above Claims 1 and 2, on the
other hand, the use of hydroxyanthraquinones as oxidising agents, in the manner
herein before described.
11. In carrying out the process defined in the above Claim 9, the production of
green dye-stuffs containing nitrogen, from mixtures of leuco quinizarin and
quinizarin, or of leuco alizarin bordeaux and alizarin bordeaux, or of leuco alizarin.
pentacyanin and pentacyanin, and from primary aromatic amines.
12. The production of dye-stuffs referred to in the claiming clause 8, by
carrying out the process defined in the Claim 3, in the presence of air.

page_text: 13. The use of the leuco compounds containing nitrogen, defined in the above
Claims 3 & 6, for the production of dye-stuffs on fibre.
14. As new articles of manufacture :-
(a.) The leuco bydroxyanthraquinones, except the quinizarin hydride No. I
herein before mentioned, and their sulphonic acids referred to in the above
Claims 1 and 2 ;-
(b) The leuco compounds containing nitrogen defined in the Claim 3 ;-
(c.) The leuco sulphonic acids obtained by the process described in the
Claim 6.
Dated this 7th day of January 1897.
NEWTON & SON,
Agents for the Applicant.