IMPROVEMENTS IN THE PRODUCTION OF COLORING MATTERS
Year: 1877

page_text: LETTERS PATENT to Reinhold Hoffmann, of Marienberg bei Bensheim, in the
Empire of Germany, Chemist, for the Invention of "IMPROVEMENTS IN THE
PRODUCTION OF COLORING MATTERS."
PROVISIONAL SPECIFICATION left by the said Reinhold Hoffmann at the
Office of the Commissioners of Patents on the 9th October 1877.
REINHOLD HOFFMANN, of Marienberg. bei Bensheim, in the Empire of Germany,
Chemist. "IMPROVEMENTS IN THE PRODUCTION OF COLORING MATTERS."
This Invention relates to the production of purple, violet, and red coloring matters
from those substances which are known as blue, green, or the so-called white ultra-
marine, or from analogous compounds thereto, and consists in submitting the same
or mixtures of the same to the action either of acids or of acid compounds, or of
such compounds which either alone or in conjunction with such acids or acid com-
pounds as are capable of liberating or evolving an acid or acids at an elevated
temperature, and this Invention consists,―
Firstly. In effecting the conversion or transformation of the ultramarines or com-
pounds analogous thereto into purple or violet colouring matters which are capable of
being employed in the arts.
And, Secondly. In the conversion of the before-mentioned purple or violet coloring
matters into red coloring matters, which are also capable of being employed in the
arts.
Thirdly. In the direct production of such red coloring matters from the before-
mentioned ultramarines or compounds, analogous thereto, by the employment of the
before-referred to acids and compounds and substances, which either alone or in
conjunction with such acids or acid compounds as are capable of liberating or evolving
an acid or acids at an elevated temperature.
In carrying out the first part of my Invention I take either what is known as the
blue, green, or white ultramarine, or compounds analogous thereto, and I submit the
same or mixtures of the same at an elevated temperature, and in presence of air to

page_text: the action either of acids or of acid compounds, or of such substances or mixtures
from which the acid necessary to effect the conversion of the ultramarine or
compounds analogous thereto into the desired purple or violet colors can be
liberated.
In carrying out the 2nd part of my Invention, I submit the purple or violet
coloring matters, obtained as before mentioned or otherwise, to the action at an
elevated temperature, either with or without the admission of air, of acids, or of acid
compounds, or of such substances or compounds which at an elevated temperature
are capable of liberating or evolving an acid or acids, and thus transforming the
before-mentioned purple or violet ultramarines into red coloring matters; or instead
of firstly converting the ultramarines, or the compounds analogous thereto, into the
purple or violet ultramarines before mentioned, and then into red coloring matters
for blue, green, or white ultramarine or compounds analogous thereto may be directly
converted into the desired red colors by submitting the ultramarines or compounds
analogous thereto, or mixtures of the same, at an elevated temperature with the
admission of air to the action of the before-mentioned acids, acid salts, or
compounds.
The acids, the acid substances, compounds or substances, which I have found
suitable, which at an elevated temperature are capable of effecting the desired con-
version of the ultramarines, or compounds analogous thereto, are acids, such as
hydrochloric acid, such acid salts as bisulphates of potash or soda, and such neutral
salts as sal ammoniac, or such other chlorides, which in conjunction with the acid
salts before mentioned are capable at an elevated temperature of evolving hydro-
chloric acid, but other acids or compounds may be employed.
Although I have referred to the compounds to be employed as ultramarines,
analogous compounds may be employed, such for example, as ultramarines in which
either the whole or a part of the sodium is replaced either by potassium or calcium,
or by other metals.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Reinhold Hoffmann in the Great Seal Patent Office on the 3rd April
1878.
REINHOLD HOFFMANN, of Marienberg bei Bensheim, in the Empire of Germany,
Chemist. " IMPROVEMENTS IN THE PRODUCTION OF COLORING MATTERS."
presence
This Invention consists in the conversion of blue, green, or so-called white ultra-
marine or mixtures of the same into a violet color, and also by continuing the
processes herein-after mentioned into a red color, both of which colors are suitable
for industrial purposes. This I effect by the action of acids, or of such substances
or compounds or mixtures as are capable of generating or evolving an acid vapor
or vapors, having the effect of an acid at an elevated temperature and in the
of air. These conversions take place very gradually, in particular, the violet color is
only obtained as an intermediate product, that is to say, as a mixture of blue and
red ultramarine, and consequently it may be produced in an unlimited variety of
shades between red and blue. The red color may also be obtained in a variety of
dark or light shades, according to the treatment adopted, the degree of temperature
used, and the quality of the ultramarine employed.
The production of the violet and red ultramarine may be effected by the processes
herein-after mentioned, videlicit,
First. By the employment of dry hydrochloric acid, dry hydrobromic acid, or dry
hydriodic acid, or mixtures of the same.
Second. By the employment of the ammoniacal salts of these acids, employed either
separately or in succession, or in combination.
Third. By the employment of substances and compounds which are capable of
generating or evolving one or more of the acids before mentioned.
The method employed for the production of violet and red ultramarine colors
consists in exposing the above-mentioned descriptions of ultramarine which are to
be converted into violet or red, either separately or mixed together to a temperature
of froin about 120° centigrade to about 200° centigrade, or in some cases to a some-
what higher temperature, and then submitting them to the action of the acid or acids,
or the vapors of the same for a sufficient length of time until the desired shade of
violet or red is obtained.
When the conversion of the blue, green, or white ultramarine or mixtures of the
same into violet or red colors by means of the solid ammoniacal salts or compounds
herein-before mentioned is to be effected, they may be employed either alone or in
conjunction with the substances or compounds herein-before referred to. When so
employed they may be added to and mixed with the previously heated descriptions
of ultramarine, or mixtures or compounds of these salts with the ultramarine may
be prepared, and these mixtures may then be brought to the required temperature.
In all these cases the presence of air is not prejudicial, but even beneficial, as it acts
either as an oxydising agent, or by rarefying the vapors of the acids and salts.
It is desirable to dry the ultramarine to be acted upon, as well as the before-
mentioned salts or compounds to be employed, as aqueous vapour retards the formation
of violet and red ultramarine colors.
According to these general rules other modifications may be adopted which will
vary, according to the ultramarine employed, and the process adopted for its conversion,
and also when employed in combination or separately.
Among such modes of proceeding the following have been selected as examples,
having been found by experiment to be well adapted for the purpose, but I do not
limit myself to the special manner indicated.
1. For the production of violet ultramarine colors I mix finely ground blue ultra-
marine, rich in color, with from two to five per cent. of sal ammoniac; this mixture is
then heated in the presence of air to about two hundred degrees centigrade, or even
somewhat higher, and maintained at this temperature, being stirred frequently until
the desired shade of color is obtained, which should approach more or less nearly to a

page_text: red color, according to the strength and duration of the treatment, and the elevation
of the temperature. A slow cooling is then allowed to take place, whereby the
colors are increased in brightness; after cooling, the products are washed with water
in order to remove the soluble salts; and lastly, are submitted to mechanical treat-
ment in order to render the colors more suitable for various industrial purposes.
2. In order to obtain red ultramarine colors I employ the violet obtained, according
to process No. 1, or by any other suitable means, and heat the same to about one
hundred and fifty degrees centigrade, or even somewhat higher, and then conduct the
vapours of dry hydrochloric acid, or of the before-mentioned acids over the same,
with occasionally stirring, until the desired shade of red is produced. The subsequent
treatment is the same as described in process No. 1 for the production of violet.
3. In order to obtain red ultramarine color of the same description as that produced
from the violet color direct from blue, or green, or white ultramarine, I heat the
latter to about one hundred and fifty degrees centigrade, and heat it as described
for violet in process No. 2, with vapors of dry hydrochloric acid, or any of the
before-mentioned acids. By this treatment violet is first produced which subse-
quently changes to red. This mode of proceeding is also suitable for producing
violet by arresting the action of the hydrochloric acid, or of the other before-
mentioned acids at the proper time. In this case also the shade of color depends to
a great extent upon the density and duration of the action of the acid vapor.
4. I also obtain a violet ultramarine color by mixing prepared red and blue
ultramarine color together.
Although I have given the before-mentioned processes as types, it will be evident
that modifications may be adopted, and the ammoniacal compounds and salts of the
before-mentioned acids in conjunction with compounds or substances capable, at an
elevated temperature, of eliminating therefrom the acids referred to, may be
substituted, or may be employed in connection therewith.
Having now described and particularly ascertained the nature of my said Invention,
and the manner in which the same is or may be used or carried into effect, I would
observe in conclusion that what I consider to be novel and original, and therefore
claim as the Invention secured to me by the herein-before in part recited Letters
Patent is,―
First. The production of violet and red ultramarine colors from blue, green, or
from white ultramarine by the employment of dry hydrochloric acid, or of dry hydro-
bromic acid, or of dry hydriodic. acid, or of mixtures of the same, substantially in the
manner herein-before described.
Second. The production of violet and of red ultramarine colors from blue, green,
or from white ultramarine by the employment of one or of more of the animoniacal
salts or compounds herein-before referred to, either alone or in conjunction with one
or more of the acids before mentioned.
Third. The production of violet and of red ultramarine colors from blue, green,
or from white ultramarine by the employment of the ammoniacal salts or compounds
before referred to in conjunction with substances or compounds which are capable
at an elevated temperature of generating or evolving one or more of the acids
herein-before mentioned.
In witness whereof, I, the said Reinhold Hoffmann, have to this my Specification
set my hand and seal, this Twenty-ninth day of March, One thousand
eight hundred and seventy-eight.