IMPROVEMENTS IN THE MANUFACTURE OF THE COLOURING MATTERS KNOWN AS INDOPHENOLS, AND A METHOD OF RENDERING THEM SOLUBLE IN WATER
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Otto Nicholas Witt and Horace
Köchlin at the Office of the Commissioners of Patents on the 30th November
1881.
OTTO NICHOLAS WITT, Ph.D., of Mulhouse, Alsace, in the Empire of Germany,
and HORACE KÖCHLIN, of Lorrach, in the Duchy of Baden. "IMPROVEMENTS IN
THE MANUFACTURE OF THE COLOURING MATTERS KNOWN AS INDOPHENOLS, AND
A METHOD OF RENDERING THEM SOLUBLE IN WATER."
In a previous Patent taken by us, No. 1373, dated the 28th day of March 1881,
we described a series of new and useful dyestuffs to which subsequently the name
of indophenols was applied. We now describe improved methods of obtaining theso
coloring matters and others of similar nature and properties.
Instead of treating a mixture of paramido derivatives of primary, secondary, and
tertiary amines with phenols, their homologues or derivatives with oxydising
agents, as described in the first Patent, the process may be reversed and a mixture
of paramido derivatives of phenols, their homologues or derivatives with primary,
secondary, or tertiary amines, may be treated with oxydising agents in solutions
which may be either acid, or neutral, or basic. As an example we will describe our
process for obtaining a blue dyestuff from paramido-phenol and dimethylaniline.
We dissolve
15 lbs. paramidophenol hydrochloride in
25 glls. of water, we then add
16 lbs. dimethylaniline hydrochloride previously dissolved in
10 glls. of water. After well stirring we introduce a solution of
20 lbs. potassic bichromate in
35 glls. of water. A blue coloration is obtained instantaneously, and the dye
stuff formed may be obtained and purified by the usual processes. This dye-
stuff is in every respect similar to the one obtained from paramidodimethylaniline
and phenol, as described in the Patent already mentioned.
Instead of water other solvents may be employed; instead of the compounds
named other compounds of the same class may be used, and we wish it to be
understood that the process given is only an example of a large number of reactions.
[Price 2d]

page_text: This reaction may also be made to take place on the textile fibre, and thus be
utilized in dyeing and printing.
We have found that in the formation of indophenols from nitroso compounds or
chloroquinoneimides and phenols the presence of alcali or a reducing agent is by no
means necessary, and that indophenols may be obtained by simple heating of the
ingredients with or without the addition of some solvent. The following
description of a process we carry out on the large scale may serve as an example.
We heat a mixture of
•
1010S. DICrosodimethylaniline
19 a napthol
"
35 spirit
"
the excess of the phenol (in this case a napthol) reacts upon the dyestuff formed
and transforms it into a compound easily soluble in alcaline lyes. To obtain a color
which is readily soluble in water we heat the above mixture until the reaction is
finished, we then add
5.5 lbs. of caustic soda and distil off the spirit. The residue may be powdered
and forms an excellent dyestuff easily soluble in warm water.
Instead of working in the manner above described we may modify our process
by treating ready formed indophenol with a suitable quantity of naptholsodium.
We may also replace part or all of the a napthol by other phenols or their homo-
logues or derivatives, a process which leads to compounds of slightly modified
properties, and we wish it to he understood that the process above described is but'
a fair example of a general reaction, the nature of which is the production of soluble
indophenols by the action of phenols or their alcaline derivatives upon the insoluble
indophenols, either in statis nascendi, or when already formed.
If in the preparation of indophenols from amido-derivatives of primary, secondary,
and tertiary amines and phenols, as described in our former Specification, an excess
of phenol be used and the solution be kept quite neutral or even slightly basic, the
products obtained likewise belong to the class of soluble indophenols.