IMPROVEMENTS IN THE MANUFACTURE OF A BLUE COLOURING MATTER OR DYE STUFF
Year: 1882

page_text: LETTERS PATENT to Frank Wirth of the firm of Wirth and Company, Patent
Solicitors, at Frankfort on the Main, in the Empire of Germany for an Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF A BLUE COLOURING MATTER OR
DYE STUFF A communication from Edward Oehler, trading under the firm
of K. Oehler, a person resident at Offenbach on the Main in the Empire of
Germany.
"
PROVISIONAL SPECIFICATION left by the said Frank Wirth at the Office
of the Commissioners of Patents on the 23rd August 1882.
FRANK WIRTH, of the firm of Wirth and Company, Patent Solicitors, at Frankfort
on the Main in the Empire of Germany "IMPROVEMENTS IN THE MANUFACTURE
OF A BLUE COLORING MATTER OR DYE STUFF" [A communication from Edward
Oehler, trading under the firm of K. Oehler, a person resident at Offenbach on the
Main in the Empire of Germany,]
The object of my invention is the production of a blue dye-stuff or coloring
matter, by the treatment of the nitroso derivatives of tertiary aromatic monamines,
especially of the nitrosodimethylaniline, in a solution of concentrated sulphuric or
phosphoric acid with sulphuretted hydrogen, or a metallic sulphide, which can be
decomposed by acids at the ordinary temperature.
For instance, one (1) part of nitrosodimethylaniline is dissolved in thirty (30)
parts of sulphuric acid of 1,4 specific gravity, and sulphide of zinc is slowly
poured in the solution. It is advantageous to keep the temperature of the mixture
under 20° Centigrade (=68° Fahrenheit).
The solution gets first a greenish color, then a blue one, and finally, when there
is enough sulphide of zinc added, it becomes colorless. Usually five (5) parts of the
sulphide of zinc for one (1) part nitrosodimethylaniline are sufficient to produce this
reaction.
The solution is then diluted with water and filtered and the decolorized liquid is
oxidized with chloride of iron. The blue coloring matter thus obtained is

page_text: precipitated by the addition of common salt and a solution of chloride of zinc, and
is separated by successive treatment with water.
I do not limit myself strictly to the above named proportions, bodies, and method
of working, which can all be changed within wide limits, for instance when the
solution of nitrosodimethylaniline in concentrated sulphuric acid is treated with
sulphuretted hydrogen or metallic sulphides, other than sulphide of zinc, it is
advantageous to let the reaction take place only until such a time as the liquid
appears of a green color, and then to treat with reducing agents, such as zinc dust or
iron, to obtain the decolorized solution. The reaction is continued in the above
described manner.
Instead of sulphuretted hydrogen and metallic sulphides I can use also the salts
or the ethers of the thiocyamic- or thiocarbonic acid or other derivatives of the
thiocyamic acid such as thiocarbamide.
The essential feature of my method is the treatment of the nitrosodimethylaniline
in a solution of concentrated sulphuric or phosphoric acid.
All other tertiary aromatic monamines which have corresponding nitrosoderivatives
can be employed; for instance from the diethyl and the ethylmethylaniline treated
in the above described manner I can also get blue dye-stuffs, but they do not offer
any advantage in comparison with that obtained from dimethylaniline.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Frank Wirth in the Great Seal Patent Office on the
20th February 1883.
"
FRANK WIRTH, of the firm of Wirth and Company, Patent Solicitors, at
Frankfort-on-the-Main in the Empire of Germany "IMPROVEMENTS IN THE
MANUFACTURE OF A BLUE COLOURING MATTER OR DYE STUFF A communication
from Edward Oehler, trading under the firm of K. Oehler, a person resident at
Offenbach-on-the-Main in the Empire of Germany
The object of my invention is the production of a blue-dye-stuff or coloring
matter by the treatment of the nitroso-derivatives of tertiary aromatic monamines,
especially of the nitrosodimethylaniline in a solution of concentrated sulphuric or
phosphoric acid with sulphuretted hydrogen, or a metallic sulphide which can be
decomposed by acids at the ordinary temperature
For instance one (1) part of nitrosodimethylaniline is dissolved in thirty (30)
parts of sulphuric acid of 1-4 specific gravity, and sulphide of zinc is slowly poured
in the solution. It is advantageous to keep the temperature of the mixture
under 20° Centigrade (=68° Fahrenheit)
The solution first assumes a greenish color, then a blue color, and finally, when
there is enough sulphide of zinc added, it becomes colorless. Usually five (5) parts
of the sulphide of zinc to one (1) part of nitroso-dimethylaniline are sufficient to
produce this reaction
The solution is then diluted with water and filtered, and the decolorized liquid
is oxidized with chloride of iron. The blue coloring matter thus obtained is
precipitated by the addition of common salt and a solution of chloride of zinc, and
is separated by successive treatment with water.
I do not limit myself to the above named proportions, bodies, and method of
working, which can all be varied within wide limits; for instance when the solution
of nitroso-dimethylaniline in concentrated sulphuric acid is treated with sulphuretted
hydrogen or metallic sulphides other than sulphide of zinc, it is advantageous to
let the reaction take place only until such a time as the liquid appears of a green
color, and then to treat with reducing agents such as zinc dust or iron to obtain the
decolorized solution. The reaction is continued in the above described manner.
Instead of sulphuretted hydrogen and metallic sulphides, I can use also the salts
or the ethers of the Thiocyamic or Thiocarbonic acid or other derivatives of the
thiocyamic acid such as thiocarbamide.
The essential feature of my method is the treatment of the nitrosodimethylaniline
in a solution of concentrated sulphuric or phosphoric acid
All other tertiary aromatic monamines which have corresponding nitroso-deriva-
tives can be employed, for instance, from the diethyl and the ethylmethylaniline
treated in the above described manner I can also get blue dye stuffs, but they do
not offer any advantage in comparison with that obtained from dimethylaniline
Having thus fully described the said invention and the manner of performing the
same I wish it understood that I claim
The production of a blue dye stuff or coloring matter by the treatment of the

page_text: nitroso-derivatives of dimethyl, diethyl, or ethylmethylaniline in a solution of
concentrated sulphuric or phosphoric acid with sulphuretted hydrogen or the above
named metallic sulphides
In witness whereof I the said Frank Wirth have hereunto set my hand and
seal this sixteenth day of February in the year of our Lord one thousand
eight hundred and eighty three.