IMPROVEMENTS IN THE MANUFACTURE OF COLORING MATTER
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Frank Wirth at the Office of the
Commissioners of Patents on the 15th September 1881. A communication
from Messrs. 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 THE
MANUFACTURE OF COLORING MATTER." [A communication from Messrs. Kalle and
Company, of Biebrich, in the Empire of Germany.]
The sulphoacids of rosaniline have by a known process been produced by treating
the rosaniline with fuming sulphuric acid having 20 per cent. of anhydride at a
temperature of from 120 to 170 centigrade. According to a further known process
it is also produced by the employment of chlorhydrine sulphate. It is known that
rosaniline cannot be transformed into the sulpho acids by means of ordinary
sulphuric acid, or with sulphuric acid having a less proportion of anhydride than
above stated. If rosaniline be heated with an excess of hydrated sulphuric acid, it
becomes almost completely decomposed at a much lower temperature under
development of sulphurous acid and formation of carbonaceous products.
According to the present Invention various sulphoacids of rosaniline are
produced by the following process:-The acid sulphates of rosaniline are, under
careful heating, converted pretty readily by water-separation into its sulpho acids.
The rosaniline forms as triple-acid base three series of salts with monobasic acids,
of which however only those having one and three acid molecules are known.
Sulphuric acid as a bi-basic acid can enter into a much greater number of com-
binations, according as only one valence or both valences thereof are saturated.
These salts are partly very unstable and cannot be isolated, but their existence is
demonstrated by the fact that while rosaniline becomes decomposed by a small excess
of sulphuric acid, a proportion of, for instance, 2 molecules of sulphuric acid and
1 molecule of rosaniline is converted into the sulphoacid under water separation at
a temperature of from 180 to 200°.
According to the present process 66 lbs. of rosaniline (or para rosaniline) are, for
example, stirred together with 44 lbs. of sulphuric acid of 60° Beaumé, previously
diluted with from 176 to 352 pints of water.
In order to render the mass of a
loose nature, about 88 lbs. of clean sand are added, and it is then evaporated to

page_text: dryness under stirring. The residue is thoroughly dried at a temperature of from
130° to 140° centigrade and powdered. The mixture is then subjected during from
5 to 6 hours to a temperature of from 180° to 200° centigrade in a vessel provided
with suitable stirrers. It is advantageous, but not absolutely necessary, to pass
during this time a neutral gas, for instance, dry carbonic acid, through the vessel.
If the operation be conducted properly, at most traces of sulphurous acid will
escape.
The mass thus treated is then boiled with water until it is exhausted, and the
liquid drawn off is super saturated with milk of lime. In this operation some
unconverted rosaniline mixed with calcium sulphate is separated, which may be
used for fresh operations.
The lime salt of the rosaniline sulpho acid in solution is converted into the soda
salt by the well known process.