Improvements in the Manufacture of Dyestuffs.
Year: 1890

page_text: Date of Application, 28th Mar., 1890
Complete Specification Left, 24th Dec., 1890-Accepted, 24th Jan., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Dyestuffs.
I, SYDNEY PITT of Sutton in the County of Surrey Gentlem in (communicated to
me from abroad by Leopold Cassella & Co., of Frankfort-on-Maine, Mmufacturing
Chemists) do hereby declare the nature of this invention to be as follows:-
My correspondents have discovered that dimethylamine acting upon fluoresceine at
a temperature of from 140° to 22.° C. produces different new dye stuffs.
By heating
these two bodies together in alcoholic solution at from about 140° to 16°. the
greater part of the fluoresceine is transformed into a product, which has the properties
of a phenol and of a weak base. They call this body dimethyl-rhodaminol; its
chlorhydrate dissolved in spirit gives a red solution with yellow fluorescence, its sodic
salt dissolved in water gives a red color. The chlorhydrate dyes animal fibres in acid
bath, and vegetable fibres, when mordanted with tannic acid and tartar-emetic a
fine red.
If instead of 140-160° C. the temperature is raised to 180° C., besides the
rhodaninol another body of pure basic character is generated which is identical with
tetramethyl-rhodamine. By further raising the temperature to 21° C. only little
rhodaminol but much rhodamine is formed together with a third body of weakly basic
nature, the alcoholic solution of which resembles in colour and fluorescence that of
rhodamine. If the temperature is further increased, for instance to 230° C. decom-
position takes place.
Similar results are obtained by working in aqueous instead of alcoholic solutions at
slightly higher temperatures.
The following is an example of applying the invention showing how the bodies
resulting from the action of methylamine upon fluoresceine may be separated.
33 kilos. of fluoresceine dissolved in 150 litres of alcohol and 30 litres of an aqueous
solution containing 40 per cent. of dimethylamine are beated in a closed vessel
(autoclave) for 12 hours to from 175° to 180° C. The contents of the vessel are
diluted with 100 litres of water and 8 kilos. of caustic soda are added. That part
of the dimethylamine which did not combine with the fluoresceine are separated by
distillation and by adding to the remaining solution at a temperature of from 70°
to 80° C. 50 kilos. acetic acid of 50% causing the rhodaminol formed to precipitate.
This may be purified by repeatedly dissolving its sodic salt and precipitating it by
means of common salt, filtering and adding some muriatic acid, which causes the
separation of crystals of the chlorhydrate of tetramethylrhodamin.
Instead of acidulating the alkaline solution with acetic acid, ether, chloroform, or
other bodies of the kind may be employed. The rhodamine is completely dissolved
by these means; it is obtained from such a solution by precipitating with muriatic
acid or by evaporation.
In place of Huoresceine its methyl- or ethyl-ethers may be used which lead to the
same results.
Dated this 28th day of March 1890.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Dyestuffs.
I, SYDNEY PITT of Sutton in the County of Surrey, Gentleman, (communicated to
me from abroad by Leopold Cassella & Co. of Frankfort-on-Main, Manufacturing
Chemists) do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement :—
My correspondents have discovered that dimethylamine acting upon fluoresceine at
a temperature of from 140° to 220° C. produces different new dye stuffs. By heating
these two bodies together in alcoholic solution at from about 140° to 160° C. the
greater part of the fluoresceine is transformed into a product, which has the properties
of a phenol and of a weak base. They call this hody dimethyl-rhodaminol; its chlor-
hydrate dissolved in spirit gives a red solution with yellow fluorescence, its sodic salt
dissolved in water gives a red color. The chlorhydrate dyes animal fibres in acid
bath, and vegetable fibres, when mordanted with tannic acid and tartar emetic a
fine red.
If instead of 140,-160° C. the temperature is raised to 180° C. besides the
rhodaminol another body of pure basic character is generated which is identical with
tetramethyl-rhodamine. By further raising the temperature to 210° C. only little
rhodaminol but much rhodamine is formed together with a third body of weakly basic
nature, the alcoholic solution of which resembles in colour and fluorescence that of
rhodamine. If the temperature is further increased, for instance to 230° C. decom-
position takes place.
Similar results are obtained by working in aqueous instead of alcoholic solutions at
slightly higher temperatures.
The following is an example of applying the invention showing how the bodies
resulting from the action of methylamine upon fluoresceine may be separated.
33 kilos. of fluoresceine dissolved in 150 litres of alcohol and 30 litres of an aqueous
solution containing 40 per cent. of dimethylamine are heated in a closed vessel (auto-
clave) for 12 hours to from 175° to 180° C. The contents of the vessel are diluted
with 100 litres of water and 8 kilos. of caustic soda are added. That part of the
dimethylamine which did not combine with the fluoresceine is separated by distillation
and by adding to the remaining solution at a temperature of from 70° to 80° C.
50 kilos. acetic acid of 50% causing the rhodaminol formed to precipitate. This may
be purified by repeatedly dissolving its sodic salt and precipitating it by means of
common salt, filtering and adding some muriatic acid, which causes the separation of
crystals of the chlorhydrate of tetramethylrhodamin.
Instead of acidulating the alkaline solution with acetic acid, ether, chloroform, or
other bodies of the kind may be employed. The rhodamine is completely dissolved by
these means; it is obtained from such a solution by precipitating with muriatic acid
or by evaporation.
In place of fluoresceine its methyl- or ethyl-ethers may be used which lead to the
same results.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The process of preparing basic dyestuffs from fluoresceine or fluoresceine ethers
by heating these substances with dimethylamine.
2. The new products which result from the process or processes herein described
and claimed.
Dated this 17th day of December 1890
CARPMAEL & Co.,
Agents for the Applicant.