IM- PROVEMENTS IN THE PRODUCTION OF COLORING MATTERS SUITABLE FOR DYEING AND PRINTING
Year: 1877

page_text: LETTERS PATENT to Heinrich Caro, Chemist to the Badische Aniline and Soda
Works, of Mannheim, in the Empire of Germany, for the Invention of "IM-
PROVEMENTS IN THE PRODUCTION OF COLORING MATTERS SUITABLE FOR
DYEING AND PRINTING."
Sealed the 14th December 1877, and dated the 9th October 1877.
PROVISIONAL SPECIFICATION left by the said Heinrich Caro at the Office
of the Commissioners of Patents on the 9th October 1877.
HEINRICH CARO, Chemist to the Badische Aniline and Soda Works, of Mannheim,
in the Empire of Germany. "IMPROVEMENTS IN THE PRODUCTION OF COLORING
MATTERS, SUITABLE FOR DYEING AND PRINTING."
Some time since Charles Lauth pointed out the existence of a new class of purple
coloring matters containing sulphur as an essential element of their constitution,
and which were obtained by the combined action of sulphuretted hydrogen and of
oxidizing bodies upon the para diamido compounds of benzole or its homologues.
This re-action however has not yet received any practical or industrial application,
chiefly because the purple coloring matters thus obtained offer neither in point of
quality nor of economy any advantage when compared with the already existing
coloring matters of a similar tint.
Now, my Invention relates to improvements in the production of coloring matters
belonging to the above class of sulphuretted compounds, so as to obtain blue coloring
matters suitable for dyeing and printing.
In carrying out my Invention I take the substance commercially known as
dimethyl aniline, and I firstly act upon it with nitric acid or with nitrous acid, or
with salts of diazo benzol, or with other diazo compounds, in order to obtain either
the nitro dimethyl aniline or the nitroso dimethyl aniline, or the so-called azo
compounds of dimethyl aniline, as is well understood by chemists. I however take,
by preference, the nitroso dimethyl aniline, which I prepare by the action of nitrous

page_text: acid or its salts upon an aqueous solution of the hydro chlorate of dimethyl aniline
I then submit the nitroso dimethyl aniline or the above-mentioned nitro or azo
compounds of dimethyl aniline to the action of reducing substances, such as nascent
hydrogen or sulphuretted hydrogen or other reducing agents, in order to obtain the
amido compound, known to chemists as dimethyl phenylen diamine or amido
dimethyl aniline. I then take a diluted aqueous solution of the compound thus
obtained, and render it strongly acid by the addition of a mineral acid or acids, such
for example as hydrochloric acid or sulphuric acid, and I then submit the solution
to the conjoint action of an oxidizing agent and of sulphuretted bydrogen in order
to obtain the desired blue coloring matter.
For the purpose of effecting the oxidation of the before-mentioned substances, I
prefer to use a diluted aqueous solution of perchloride of iron or of bichromate of
potash, but other oxidized agents may be employed.
The sulphuretted hydrogen may be employed either in its aqueous condition or
dissolved in water, or be liberated in the acid mixture from such compounds as are
capable of liberating sulphuretted hydrogen in the presence of an acid.
In order to obtain the blue coloring matter resulting from the conjoint action of
oxydising agents and of sulphuretted hydrogen, I add in slight excess the oxidizing
substances, as, for instance, a solution of perchloride of iron to the acid and diluted
solution of the above-mentioned dimethyl phenylene diamine, and afterwards
sulphuretted hydrogen is either added to or is generated in the solution in a slight
excess, whereby the mixture assumes a blue color. I prefer however, firstly, to
saturate the diluted and acid solution of dimethyl phenylene diamine with sul-
phuretted hydrogen, and afterwards gradually to mix with it the oxidizing agent,
until the latter is in slight excess. The coloring matter may then be separated and
purified by precipitating it from the liquid by the addition of a suitable precipitant,
such as, for instance, a mixture of common salt and chloride of zinc, and the preci-
pitate thus obtained may be collected on a filter, and the soluble coloring matters
contained therein be extracted with water, until no more of the blue colouring
matters are dissolved. The resulting blue solution containing the desired colouring
matters suitable for dyeing and printing may again be subjected to the action of a
precipitant, in order that the coloring matters may be separated therefrom and be
obtained in a solid condition.
Although I have only mentioned the dimethyl compound of aniline, similar results
may be obtained by employing the dimethyl compounds of some of the homologous
bases, such as ortho toluidine, and instead of the dimethyl derivatives of the said
bases their dimethyl compounds or other tertiary amines may be employed, but, as
before stated, I prefer to use the dimethyl aniline.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Heinrich Caro in the Great Seal Patent Office on the 8th April
1878.
HEINRICH CARO, Chemist to the Badische Anilin and Soda Works, of Mannheim,
in the Empire of Germany. " IMPROVEMENTS IN THE PRODUCTION OF COLORING
MATTERS SUITABLE FOR DYEING AND PRINTING."
Sometime since Charles Lauth pointed out the existence of a new class of purple
coloring matters containing sulphur as an essential element of their constitution,
and which were obtained by the combined action of sulphuretted hydrogen and of
oxidizing agents upon the para diamido compounds of benzole or its homologues.
This re-action however has not yet received any practical or industrial application,
chiefly because the purple coloring matters thus obtained offer neither in point of
quality nor of economy any advantage when compared with the already existing
coloring matters of a similar tint.
Now my Invention relates to improvements in the production of coloring matters
belonging to the above class of sulphuretted compounds so as to obtain blue coloring
matters suitable for dyeing and printing.
In carrying out my Invention I take the substance commercially known as
dimethyl aniline, and I firstly act upon it with nitric acid, or with nitrous acid, or
with salts of diazo benzol, or with other analagous diazo compounds, in order to
obtain either the mononitro-dimethyl aniline or the nitroso dimethyl aniline, or the
so-called azo compounds of dimethyl aniline, as is well understood by chemists. I
however take by preference the nitroso dimethyl aniline, which I prepare by the
action of nitrous acid or its salts, upon an aqueous solution of, for example, the
hydrochlorate of dimethyl aniline. I then submit the nitroso dimethyl aniline or
the above-mentioned mononitro or azo compounds of dimethyl aniline to the action
of reducing agents, such, for example, as nascent hydrogen, or sulphuretted hydrogen,
or other reducing agents, in order to obtain the para amido derivative of dimethyl
aniline known to chemists as dimethyl phenylene diamine or amido dimethyl
aniline. I then take a diluted aqueous solution of the compound thus obtained and
render it strongly acid by the addition of a mineral acid or acids, such, for example,
as hydrochloric or sulphuric acid, and I then submit the solution to the action of an
oxidizing agent and of sulphuretted hydrogen in order to obtain the desired blue
coloring matters.
In order to effect the oxidation of the before-mentioned substances I prefer to use
a diluted aqueous solution of perchloride of iron or of bichromate of potash, but
other oxidizing agents may be employed.
Sulphuretted hydrogen may be employed, either in its gaseous condition or
dissolved in water, or be liberated in the acid mixture from such compounds as are
capable of liberating sulphuretted hydrogen in the presence of an acid.
In order to obtain the blue coloring matters resulting from the action of oxidizing
agents and of sulphuretted hydrogen, I add in slight excess the oxidizing substances,
as, for instance, a solution of perchloride of iron to the acidified and diluted solution
of the above-mentioned dimethyl phenylene diamine, and afterwards sulphuretted
hydrogen is either added to or is generated in the solution in a slight excess, whereby
the mixture assumes a blue color. I prefer however firstly to saturate the dilute
and acid solution of dimethyl phenylene diamine with sulphuretted hydrogen, and
afterwards gradually to mix with it the oxidizing agent until the latter is in slight
excess. The coloring matters may then be separated and purified by precipitating
them from the solution by the addition of a suitable precipitant, such, for example,
as a mixture of common salt and chloride of zinc, and the precipitate thus obtained
may be collected on a filter, and the soluble coloring matters contained therein be
extracted with water, until no more of the blue coloring matters are dissolved.

page_text: The resulting blue solution containing the desired coloring matters suitable for
dyeing and printing may again, if necessary, be subjected to the action of a pre-
cipitant in order that the coloring matters may be separated therefrom and be
obtained in a solid condition.
Although I have only mentioned the dimethyl compound of aniline, similar results
may be obtained by employing the dimethyl compounds of some of the homologous
bases, such as ortho toluidine, and instead of the dimethyl derivatives of the said bases
their diethyl compounds or other tertiary monamnines, such as methyl or ethyl
diphenyl amine, may be employed, but, as before stated, I prefer to use the dimethyl
aniline.
As an example of the manner in which I prefer to carry out my Invention I
proceed as follows:-About ten pounds of dimethyl aniline are mixed with about
thirty pounds of concentrated muriatic acid and with about twenty gallons of cold
water, and to the solution thus obtained I add gradually, and with constant stirring,
a solution of commercial nitrite of sodium, containing about 5-7 pounds of pure
nitrite of sodium. The mixture soon assumes an intensely yellow color, and at
the termination of the operation or re-action which I have found to be practically
terminated in the space of from about four to about five hours, the mixture will be
found to contain the compound known to chemists as the hydrochlorate of nitroso
dimethyl aniline. The mixture is then diluted with about 50 gallons of cold water,
and is rendered strongly acid by the addition of about thirty pounds of concentrated
muriatic acid. In order to effect the reduction of the nitroso compound a strong
current of sulphuretted hydrogen is then passed through the mixture until its
yellow color is destroyed and an almost colorless solution obtained, which contains
the amido derivative of dimethyl aniline known to chemists as amido dimethyl
aniline or dimethyl phenylene diamine.
Instead of employing sulphuretted hydrogen in its gaseous condition the sanie
may be generated in the mixture by adding thereto in small portions at a time,
and until the reduction is complete, either the sulphides of potassium, sodium,
ammonium, or calcium, or any other sulphides which are readily decomposable by
dilute acids, such, for example, as muriatic acid.
In order to produce blue coloring matters from this re-action I firstly take care
that the solution of the amido dimethyl aniline is completely saturated with sul-
phuretted hydrogen, and I then add gradually and in small portions at a time about
twenty gallons of a diluted aqueous solution of perchloride of iron, of about 1.07
specific gravity, until the sulphuretted hydrogen contained in the solution has been
decomposed, and the oxidizing agent employed exists in slight excess. During this
operation the mixture gradually assumes a deep blue color, and in order to separate
the coloring matters therefrom the mixture is saturated by preference with common
salt, and a sufficient quantity of an aqueous solution of chloride of zinc is then
added in order to precipitate the coloring matters. The precipitate thus obtained
is separated by filtration or otherwise, and the coloring matters, which are soluble
in water, may be extracted by successive treatments with cold or with tepid water.
The filtered solutions of the same are then suitable for the purposes of dyeing and
printing, and in order to obtain the coloring matters in a solid condition therefrom
the solutions of the coloring matters may be again saturated with common salt,
and precipitated with a solution of chloride of zinc, and the precipitate thus
obtained may be separated by filtration, pressed, and dried.
Having thus described the nature of my said Invention, and the manner of
performing the same, I wish it to be understood that I do not confine myself to
the exact details described; but what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before in part recited
Letters Patent is, the production of blue coloring matters suitable for the purposes
cf dyeing and printing from dimethyl aniline and from other tertiary monamines
by firstly converting the same into their para amido derivatives, and then acting

page_text: upon the latter compounds with sulphuretted hydrogen and oxydizing agents,
substantially in the manner as herein-before described.
In witness whereof, I, the said Heinrich Caro, have to this my Specification
set my hand and seal, this Fifth day of April, One thousand eight hundred
and seventy-eight.
HEINRICH CARO. (L.S.)