IMPROVEMENTS IN COLORING MATTER
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Frank Wirth at tlie Office of the
Commissioners of Patents on the 17th July 1883. A communication from
Heinrich Baum, chemist, a person resident at Höchst on the Main, Germany.
FRANK WIRTH of the firm of Wirth and Company, Patent Solicitors at Frankfort
on the Main in the Empire of Germany, "IMPROVEMENTS IN COLORING MATTER."
[a communication from Heinrich Baum, chemist, a person resident at Höchst on
the Main, Germany.]
"
This Invention relates to the preparation of coloring matters by the action of
the organic acid anhydrides on the Halogen salts of the primary, secondary, and
tertiary aromatic Amines with or without the application of dehydrating agents.
The novelty consists in the formation of coloring matters by heating the Halogen
salts of the aromatic bases with organic acid anhydrides even without the use
of dehydrating agents such as Zn Cl₂, Al, Cl, etc, at temperatures which do not rise
above 200° C.
If anhydrous chloranilin is heated with 1/2 to twice its weight of acetic
anhydride in a closed vessel at a temperature of 150° to 200° C for 12 hours, a
thick syrupy, brownish-yellow mass is obtained which shows a greenish yellow
fluorescence. When poured into water a brownish-yellow resin separates from the
mass which is insoluble in hot water, but is soluble in dilute hydrochloric acid. If this
resin is heated with a dilute solution of caustic soda, no aniline is obtained, a proof
that no acetanilide has been formed in the mass. The dark brown looking base
obtained by boiling with caustic soda solution when treated with hydrochloric
On
acid is, however, converted into the original salt which is insoluble in water.
the other hand, if the resin is boiled for some time with dilute sulphuric acid,
acetic acid escapes and the base, which is thrown down by an excess of caustic
soda, gives, when treated with hydrochloric acid, a yellow colored salt easily soluble
in water; concentrated hydrochloric acid discharges the color of it.
By this process then is formed the chloracetyl derivative of a yellow coloring
matter which is easily converted into the coloring matter by boiling with dilute
sulphuric acid. By using at the same time dehydrating agents, such as fer
instance completely anhydrous zinc chloride, chloride of aluminium, etc, the action
is somewhat hastened; at the same time their use is not a necessity. By substi-
tuting the aromatic bases for aniline, as for instance Toluidine, Xylidine,

page_text: Naphthylamine, etc, coloring matters of different shades are obtained.
The salts
of hydrochloric acid can then be replaced by the corresponding bydriodic and
hydrobromic acid salts. Further, by this process the acetanhydride can be replaced
by its homologues, as for instance valerianic anhydride as also by the mixed
anhydrides of the fatty acid series, as for instance propionacetanhydride. Equally
applicable are the anhydrides of the aromatic series as well as the mixed anhydrides
of these and those of the most acid of the aromatic and fatty acids, as for instance
acetobenzoicanhydride.
An instance will show the method of preparing the coloring matter:-12 kilo-
grammes chloraniline are beated in a suitable vessel with 18 kilogrammes acetic
anhydride for twelve hours at a temperature of 180° to 200° C. The mass thus
°
obtained is poured into five times its bulk of water. Hereby the greater part of
the coloring matter separates as a reddish-yellow resin, the mother liquor still
retaining some coloring matter and some of the aniline salt which has not been
acted on.
The separated resin is boiled in suitable retorts with five times its bulk
of water containing from 20 to 30% of sulphuric acid until the distillate is free
from acetic acid. The solution is then allowed to cool, is filtered and then treated
with an excess of soda or caustic soda lye. The precipitated base is dissolved in a
little hydrochloric acid and water, and the coloring matter thrown down by means
of common salt, and finally it is obtained in the pure state by redissolving in a
dilute solution of common salt; when pulverised it dies silk, wool, and cotton a
magnificent green yellow.