Manufacture of Dyestuffs from Substituted Fluoresceïns.
Year: 1895

page_text: Date of Application, 8th Apr., 1895
Complete Specification Left, 8th Jan., 1896-Accepted, 8th Feb.,
1896
[Communicated from abroad by THE FARBWERKE, vormals MEISTER LUCTUS
AND BRUNING, of Hoechst a/ Main, in the Empire of Germany, Chemical
Manufacturers.]
Manufacture of Dyestuffs from Substituted Fluoresceïns.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, do hereby declare the nature of
this invention to be as follows:-
Tetrabromfluoresceïn, on being strongly heated with concentrated sulphuric acid,
produces a "bromocoeruleïn which was first mentioned by Baeyer in Liebig's
Annalen volume 183.
"
To obtain this compound Baeyer heated eosine with concentrated sulphuric acid
up to the boiling point. By this method, however, as Baeyer remarks, only a small
quantity of the pure substance is obtained, along with a great quantity of dirty
bye-products possessing weak tinctorial properties, probably in consequence of the
high temperature.
On the other hand the conversion of eosine into the above bromocoeruleïn either
does not succeed or is but very imperfectly effected by means of ordinary concentrated
sulphuric acid at lower temperatures.
Thus Baeyer's method appears unsuitable for the manufacture of dyestuffs of
the nature of coeruleine from substituted fluoresceïns, and hitherto there has been
no known technical application of these observations of Baeyer.
My foreign correspondents. have made an essential, technically important
improvement in the manufacture of dyestuffs of the nature of coeruleïn by
employing sulphuric acid free from water (monohydrate) or still better sulphuric
acid containing sulphuric anhydride (fuming sulphuric acid) instead of ordinary
concentrated sulphuric acid which as a rule contains from 5 to 3 per cent. of water.
By this means a disturbance of the reaction by the water which is probably formed
is prevented.
The conversion of substituted fluoresceïns into dyestuffs of coerulein nature is
effected completely under these conditions at a considerably lower temperature,
secondary reactions and decompositions are avoided, and dyestuffs are obtained in
large yield possessing strong tinctorial properties and very fast to air, light and
воар. The percentage of sulphuric anhydride in the fuming sulphuric acid
employed can be varied within considerable limits, the temperature which is
necessary and the duration of the heating depending on the strength of the acid
employed.
EXAMPLE I.
1 part by weight of cosine (tetrabromfluoresceïn) is stirred into 5 parts by
weight of fuming sulphuric acid, containing 20 per cent. sulphuric anhydride and
heated to a temperature of 125° to 130° C. until a test portion treated with exces:
of aqueous alkali and some salt solution gives a weak rose coloured filtrate. This
point is reached after about 45 minutes. After cooling, the melt is poured into
water which precipitates the dyestuff in dark, almost black, flakes.
The dyestuff is filtered and washed, and may either be obtained as a paste of an
almost black colour ready for use, or may be dissolved with soda and filtered,

page_text: the sodium salt being then salted out of the filtrate, pressed and dried. The
sodium salt is a black powder which on being strongly rubbed assumes a weak
bronze lustre.
The dyestuff is soluble in alkalies with bluish green colour, in concentrated
sulphuric acid with dark cherry red colour; it is insoluble in water and very
sparingly soluble in alcohol. It dyes wool mordanted with chrome a strong and
brilliant bluish green.
They have also discovered that the substances obtained in the manner above
described suffer a further change if, after being heated with fuming sulphuric acid,
they are again heated with a sulphuric acid containing a little water to temperatures
of from 130° to 150° C. The product then dyes a greener shade and is faster to
milling than before it was heated with sulphuric acid containing water, and exhibits
the difference that the bluish green colour of its alkaline alcoholic solutions is fast
to light, whereas the colour of the dyestuff heated with fuming sulphuric acid only,
disappears after a short time.
EXAMPLE II.
1 part by weight of the dried free dyestuff, obtained according to Example I, is
heated with 10 parts by weight of ordinary concentrated sulphuric acid for
2 to 3 hours at 150° C.; this is precipitated by pouring into water, and, after
washing, the dyestuff is obtained in the form of paste, or, after being converted
into the sodium salt, by dissolving it in soda, it is salted out pressed and dried.
It is advantageous to combine the operations described in Examples I and II
into a single operation in the following manner :
EXAMPLE III.
1 part by weight of eosine is first heated with 5 parts by weight of fuming
sulphuric acid containing 20 per cent. sulphuric anhydride for three quarters of
an hour at a temperature from 125° to 130° C., then by the addition of some
water either in the form of ice or of sulphuric acid containing water the
excess of sulphuric anhydride is removed and the mixture is then heated for
from 2 to 3 hours at 150° C. During this second heating halogen is, set free to a
noticeable extent.
After pouring into water the separation of the dyestuff takes place as
Example II.
in
Like tetrabromofluoresceïn the iodine-substitution products of fluorescein, the
bisubstitution products of fluorescein as well as the corresponding derivatives of the
chlorofluoresceïns, obtained from the chlorophthalic acids and resorcine, may be
treated by the above method. The manufacture of coerulein dyestuffs from these
substances is carried out in the same manner as in the case of cosine in the above
examples.
Dated this 8th day of April 1895.
ABEL & IMRAY,
Agents for the Applicant.
Manufacture of Dyestuffs from Substituted Fluoresceïns.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the 4
County of London, Chartered Patent Agent, 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 :-
Tetrabromofluoresceïn, on being strongly heated with concentrated sulphuric

page_text: "
acid, produces a ❝ bromocoeruleïn' which was first mentioned by Baeyer in
Liebig's Annalen volume 183.
To obtain this compound Baeyer heated eosine with concentrated sulphuric acid
up to the boiling point. By this method, however, as Baeyer remarks, only a
small quantity of the pure substance is obtained, along with a great quantity of
dirty bye-products possessing weak tinctorial properties, probably in consequence
of the high temperature.
On the other hand the conversion of cosine into the above bromocoeruleīn
either does not succeed or is but very imperfectly effected by means of ordinary
concentrated sulphuric acid at lower temperatures.
"
Thus Baeyer's method appears unsuitable for the manufacture of dyestuff's of
the nature of coeruleïne from substituted fluoresceïns, and hitherto there has been
no known technical application of these observations of Baeyer.
My foreign correspondents have made an essential, technically important
improvement in the manufacture of dyestuffs of the nature of coerulein by
employing sulphuric acid free from water (monohydrate) or still better sulphuric
acid containing sulphuric anhydride (fuming sulphuric acid) instead of ordinary
concentrated sulphuric acid which as rule contains from 5 to 3 per cent. of water.
By this means a disturbance of the reaction by the water which is probably formed
is prevented.
The conversion of substituted fluoresceïns into dyestuffs of coerulein nature
is effected completely under these conditions at a considerably lower temperature,
secondary reactions and decompositions are avoided, and dyestuffs are obtained in
large yield possessing strong tinctorial properties and very fast to air, light and
soap. The percentage of sulphuric anhydride in the fuming sulphuric acid
employed can be varied. within considerable limits, the temperature which is
necessary and the duration of the heating depending on the strength of the acid
employed.
EXAMPLE I.
1 part by weight of eosine (tetrabromofluoresceïn) is stirred into 5 parts by
weight of fuming sulphuric acid, containing 20 per cent. sulphuric anhydride and
heated to a temperature of 125° to 130° C. until a test portion treated with excess
of aqueous alkali and some salt solution gives a weak rose coloured filtrate.
point is reached after about 45 minutes. After cooling, the melt is poured into
water which precipitates the dyestuff in dark, almost black, flakes.
This
The dyestuff is filtered and washed, and may either be obtained as a paste of an
almost black colour ready for use, or it may be dissolved with soda and filtered,
the sodium salt being then salted out of the filtrate, pressed and dried. The
sodium salt is a black powder which on being strongly rubbed assumes a weak
bronze lustre.
The dyestuff is soluble in alkalies with bluish green colour, in concentrated
sulphuric acid with dark cherry red colour; it is insoluble in water and very
sparingly soluble in alcohol.
It dyes wool mordanted with chrome a strong and brilliant bluish green.
They have also discovered that the substances obtained in the manner above
described suffer a further change if, after being heated with fuming sulphuric
acid, they are again heated with a sulphuric acid containing a little water to
temperatures of from 130° to 150° C. The product then dyes a greener shade
and is faster to milling than before it was heated with sulphuric acid containing
water, and exhibits the difference that the bluish green colour of its alkaline
alcoholic solutions is fast to light, whereas the colour of the dyestuff heated with
fuming sulphuric acid only, disappears after a short time.

page_text: heated with 10 parts by weight of ordinary concentrated sulphuric acid for 2 to
3 hours at 150° C.; this is precipitated by pouring into water, and, after washing,
the dyestuff is obtained in the form of paste, or, after being converted into the
sodium salt, by dissolving it in soda, it is salted out pressed and dried.
It is advantageous to combine the operations described in Examples I and II
into a single operation in the following manner :
EXAMPLE III.
1 part by weight of eosine is first heated with 5 parts by weight of fuming
sulphuric acid containing 20 per cent. sulphuric anhydride for three quarters of an
hour at a temperature from 125° to 130° C., then by the addition of some water
either in the form of ice or of sulphuric acid containing water the excess of
sulphuric anhydride is removed and the mixture is then beated for from 2 to
3 hours at 150° C. During this second heating, halogen is set free to a noticeable
extent.
After pouring into water the separation of the dyestuff takes place as in
Example II.
Like tetrabromofluorescein the iodine-substitution products of fluorescein, the
bisubstitution products of fluorescein as well as the corresponding derivatives of the
chlorofluoresceïns, obtained from the chlorophthalic acids and resorcine, may be
treated by the above method. The manufacture of coeruleïn dyestuffs from these
substances is carried out in the same manner as in the case of eosine in the above
⚫examples.
.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The herein described manufacture of dyestuff's from substituted fluoresceins
by heating substituted fluoresceins with sulphuric acid free from water or containing
sulphuric anhydride or by subjecting the products obtained as above to a further
heating with sulphuric acid containing water.
2. In the manufacture set forth in Claim 1. the employment of tetrabromo-
fluorescein, dibromofluorescein, dichlorofluoresceïn, dichlorotetrabromofluorescein,
dichlorotetraiodofluorescein, tetrachlorotetrabromo- and tetrachlorotetraiodo-
.fluoresceïn.
3. The dyestuffs manufactured as set forth in Claims 1 and 2.
Dated this 8th dan of Tanna 1000
ABEL & IMRAY,
Agents for the Applicant.