IMPROVEMENTS IN BLUE COLOURING MATTER
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Frank Wirth at the Office of the
Commissioners of Patents on the 17th January 1883. A communication
from Mess" Kalle and Company of Biebrich in the Empire of Germany
FRANK WIRTH of the firm of Wirth and Company, Patent Solicitors, at
Frankfort on the Main in the Empire of Germany "IMPROVEMENTS IN BLUE
COLOURING MATTER [A communication from Mess" Kalle and Company of
Biebrich in the Empire of Germany]
"
This invention relates to the production of a blue coloring matter more or less
green called Benzylenblue which is derived from the salts of the Aromatic
Quaternary Amines (Ammonium bases) and particularly from the Dimethylphe-
nylbenzylammonium chloride which is produced if the Nitroso-compounds of these
bases be treated in proper proportions with Sulphuretted hydrogen and the so
formed Leuco base converted into the proper coloring matter by employing
oxidizing media.
The manufacture of the colouring matter therefore takes place in three stages.
(1) Production of the Nitroso combination of the respective Ammonium base
(2) Conversion of this Nitroso compound into a sulphurous base.
(3) Conversion of this Leuco base into the coloring matter and purification of
the same.
1st Operation. The production of Nitroso compounds from the salts of
quaternary aromatic bases (Ammonium bases) in a direct way ie, by the action of
hyponitrous acid on these bases can only be effected with difficulty and imperfectly.
The result is more easily attained inasmuch as the Nitroso compounds of the
respective tertiary aromatic amines are first produced and these then combined
with Alkylhalogens.
CH,
AB

page_text: contains in the main the desired Nitroso-compound the acid solution of which
possesses a cherry red color (The acid solution of the Nitrosodimethylaniline
appears straw colored beside it.)
in 600 Kilos of hydrochloric acid of 1.2 sp. gr. or 600 Kilos of sulphuric acid of
1.4 sp. gr. warmed up to 50° and SH, passed into it, or a suitable sulphido (SH)
combination introduced (for instance sulpho bases) until the cherry red solution is
quite decolorised. The Nitroso-compound has through this treatment become
converted into a colorless sulphur base which easily permits of conversion into the
blue coloring matter by the action of oxidizing media.
3rd Operation. I now dilute the solution of the colorless base with 600 Kilos
water, filter and allow a solution of chloride of iron containing in 10 parts,
1 part of strong chloride of iron, to flow into the filtrate with constant stirring
until no more coloring matter is thereby produced.
I now add 30 Kilos of chloride of zinc solution at 40° Beaumé to the deep blue
solution and then saturate the same with common salt. The coloring matter
thereby separates in resinous masses having a coppery lustre, which after a short
time may easily be collected together by filtration. In this state the coloring
matter is not yet pure enough for use in the dye works, therefore I dissolve it
again in 100 parts of water and reprecipitate it with common salt. After filtration
the coloring matter is now dried and powdered.
If in the above process the corresponding Nitroso compound of other tertiary
Amines be employed in place of Nitrosodimethylaniline, or the equivalent quantities
of other Alkylhalogens in place of Benzylchloride, then coloring matters are
produced which are only distinguishable from the Benzylenblue by slight differences
of nuance but their production is however far more expensive. Finally I obtain
the same result if instead of the above Nitroso-compound I, employ under similar
circumstances the more difficultly obtained Nitroso-compounds.
By using the above mentioned proportions and temperature the result as regards
quality and quantity of the coloring matter obtained is very favorable. I do not
however limit myself only to these, inasmuch as the respective colorless bases are
produced (if not so easily) at a lower temperature and in more diluted solutions,
and can be further by any convenient means of oxidation converted into the blue
coloring matter.
This new coloring matter Benzylenblue dissolves easily in water, and is analogous
in its constancy or lasting properties to the Aromatic Ammonium bases from
which it is derived, in its resistance against acids and alkalies and even chlorine
and bleaching powder. It owes its constancy on the fibre in the printing and
dyeing process to the property of forming with tannates insoluble blue
combinations