The Manufacture and Production of New Dyes related to the Rhodamine Series.
Year: 1891

page_text: Date of Application, 31st Aug., 1891
Complete Specification Left, 20th May, 1892-Accepted, 25th June, 1892
PROVISIONAL SPECIFICATION.
The Manufacture and Production of New Dyes related to the
Rhodamine Series.
I JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex,
Gentleman, do hereby declare the nature of this invention which has been com-
municated to me from abroad by the Badische Anilin & Soda Fabrik of Ludwig-
shafen on Rhino in the Empire of Germany, to be as follows:-
This invention is based upon the discovery that the tetra-alkylated rhodamines
can by suitable means be converted into new dyestuffs possessing properties
differing in many respects from, and giving in each case shades of colour yellower
than, the dyes from which they are derived.
This conversion of tetra-alkylated rhodamines into the new dyes is the result of
a chemical change in the former which consists in the splitting off of one or more
of the alkyl groups. This effect can be brought about in various ways, such as,
for instance, by heating the tetraalkyl-rhodamine alone or by heating it with an
indifferent diluent such as naphthalene; or by heating it with a diluting material
such as aniline hydrochlorate which acts partly as a solvent and partly as 'a
chemical reagent in that it combines with the alkyl and forms alkylated aniline.
compounds; or by heating it with suitable inorganic salts such as zinc chloride.
In each case the reaction should be suitably moderated, and interrupted when the
desired shade is obtained.
Although I mention these methods of obtaining the desired partially de-alkylated
rhodamines as instances of the ways in which the invention can be carried out, I do
not limit myself to those ways.
The tetra-alkyl-rhodamines which have hitherto yielded good results are those
of the phthalic and succinic acid series, benzo-rhodamines and those of the formic
acid sories.
These latter may be obtained by condensing dialkyl-meta-amido-phenol with
formic aldehyde and subsequently splitting off water from, and oxidising, the
product. This invention can however be applied to other tetra-alkyl-rhodamines.
The new dyestuffs yield beautiful shades of colour and are in part characterized
by a high degree of affinity for unmordanted vegetable fibre and thus appear
specially suited for dyeing mixed cotton and silk goods.
Dated this 31st day of Amit 1801
J. H. JOHNSON & Co.,
Agents
COMPLETE SPECIFICATION.
The Manufacture and Production of New Dyes related to the
Rhodamine Series.
1, JAMES YATE JOHNSON, of 47 Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, do hereby declare the nature of this invention (which has
been communicated to me from abroad by the Badische Anilin & Soda Fabrik,
of Ludwigshafen on Rhine, in the Empire of Germany) and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement :-
This invention is based upon the discovery that the tetra alkylated rhodamines
can by suitable means be converted into new dyestuffs possessing properties
differing in many respects from, and giving in each case shades of colour which are
yellower than those given by the dyes from which they are derived.

page_text: :
This conversion of tetra-alkylated rhodamines into the new dyes is the result
of a chemical change in the former which consists in the splitting off or elimina-
tion of a portion of the alkyl. This effect can be brought about in various
ways;such as,. for instance, by heating the tetra-alkylrhodamine alone; or by
heating it with an indifferent diluent such as naphthalene, or phenol, or by heating
it with a diluting material such as aniline hydrochlorate and analogues thereof
viz. the hydrochlorates of ortho- and para-toluidine; of alpha naphthylamine;
and so on, which may act partly as. solvents and partly as chemical reagents
in that, they combine with the alkyl and form alkylated amido-compounds;, or
by, heating it with suitable inorganic compounds such for example as zinc-chloride,
sulphuric or hydrochloric acid. In each case the reaction should be suitably
moderated, and interrupted, when the desired shade is obtained as prolonged
treatment gives less valuable or worthless results.
Although I'mention these methods of obtaining the desired partially de-alkylated
rhodamines, as instances of the ways in which the invention can be carried out I
do not limit myself to those ways.
The tetra-alkyl-rhodamines which have hitherto yielded good results are those
of the phthalic and succinic acid series, benzo-rhodamines and those of the formic
acid series. These latter may be obtained by condensing. dialkyl-meta-amido-
phenol with formic aldehyde and subsequently splitting off water from, and
oxidizing, the product. This invention can however be applied to other tetra-
alkyl-rhodamines.
The new dyestuffs yield beautiful shades of colour and are in part characterized
by a high degree of affinity for unmordanted vegetable fibre and thus appear
specially suited for dyeing mixed 'cotton and silk goods.
To illustrate the invention and the manner in which it can be carried into
practical effect I give by way of example the following directions for the prepara-
tion of some of the new dyes. These examples are typical and can be generally
applied 'and 'are capable of considerable variation in many respects as will be readily
understood by chemists.
The parts are by weight.
EXAMPLE 1.
Heat about three parts of tetra-ethyl rhodamine (of the phthalic acid series) in
a large enamelled pot in an oil bath. Raise the temperature of the oil bath to
from about two hundred and thirty, to two hundred and thirty-five, degrees centi-
grade, and maintain the heat, whilst keeping the mass well mixed, for from about
two and a half to three hours, or until the crystals of the initial material are
changed to a pasty mass possessing a bronze-like sheen. This point being reached
allow the mass to cool, break it up, and dissolve it in about forty parts of hot
water acidified with hydrochloric acid; filter and precipitate the solution with
common salt solution.
Repeat these operations until the desired purity is attained and then recrystallize
from hot water.
EXAMPLE 2:
Mix together about, three parts of the aforesaid tetra-ethyl-rhodamine- and
about three parts of aniline hydrochlorate in an enamelled vessel, furnished with
a stirrer and melt the mixture by heating gradually to about one hundred and
ninety degrees centigrade.. Stir well and maintain the heat for about two hours.
In applying this new process of dealkylation or. splitting off alkyl-groups to this
(as also to any) tetra-alkyl rhodamine, whether by heating alone, or with some
other body, as herein before mentioned, the course of the reaction and the point
when it should be interrupted can be ascertained by drawing samples, from time to
time, working up, and making experimental dye-tests. The heating is continued
in each case until the samples shew that the desired shade is obtained! Ashort
period of heating results in the production of shades-less yellow than those which

page_text: can be obtained by a longer period of heating but if the heating be too prolonged
the product obtained is impure and has not the desired solubility in water.
When the desired point is reached, allow the melt to cool, dissolve.in hot water
rendered slightly acid with hydrochloric acid, filter if necessary, and precipitate
the solution with common salt solution. Repeat this purification as often as iR
necessary and finally recrystallize from hot water slightly acidified with hydro-
chloric acid.
EXAMPLE 3.
Mix together about three parts of tetraethyl-rhodamine (phthalic acid), in the
form of sulphate, and about fifteen parts of dilute sulphuric acid containing say,
about from five, to seven and a half per cent. of real acid (H, SO) and heat the
mixture in a lead-lined vessel, capable of withstanding pressure, to a temperature of
from one hundred and ninety, to one hundred and ninety-five, degrees centigrade
for about eight hours. Under these conditions a pressure of- about fourteen
atmospheres developes. After cooling, dissolve the product in hot water, filter,
and salt out the colouring matter from the solution with common salt solution.
Collect the precipitate, dissolve in about thirty parts of hot water, and let the
solution stand, in the cold. After some time the colouring matter separates in the
crystalline form. Collect and dry at a low temperature.
In the above examples the process is described as applied to tetra-ethyl-
rhodamine of the phthalic acid series but if the other tetra-alkyl-rhodamines be
similarly treated, analogous results are obtained.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. The manufacture of new dyes related to the rhodamine series by splitting off
or eliminating a portion of the alkyl from tetra-alkyl-rhodamines substantially_as
heroin explained.
2. The manufacture of new dyes related to the rhodamine series by heating a
tetra-alkyl-rhodamine, either alone, or in admixture with a solvent, or diluent, or
with some substance capable of assisting a partial dealkylation, substantially as
bereinbefore described.
3. The manufacture of new dyes related to the rhodamine series by subjecting
tetra-ethyl-rhodamine of the phthalic acid series, or its analogues, to a dealkylating
treatment all substantially as hereinbefore described in the several examples
hereinbefore given.
4. As new articles of manufacture the new dyes, being partially dealkylated
rhodamines such as can be obtained' substantially as hereinbefore described.
Dated this 20th day of May 1892
J. H. JOHNSON & Co.,
Agents.