Improvements in the Preparation of Eosin and other Halogen Derivatives of the Fluorescein Group.
Year: 1899

page_text: Date of Application, 13th Feb., 1899
Complete Specification Left, 6th Nov., 1899--Accepted, 9th Dec., 1899
Improvements in the Preparation of Eosin and other Halogen
Derivatives of the Fluorescein Group.
A communication from abroad by LA SOCIETE CHIMIQUE DES USINES DU RHÔNE,
anciennement GILLIARD, P. MONNET ET CARTIER, of Lyons, France,
Manufacturers.
I, GEORGE BELOE ELLIS, of the Firm of J. C. Mewburn & Ellis, of 55 and 56,
Chancery Lane, in the County of London, Chartered Patent Agents, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the preparation of eosin and other halogen derivatives
of the fluorescein group. According to this invention an electric current is
employed in the preparation.
The methods hitherto employed for the introduction of halogens into compounds
of the fluorescein group suffer more or less from the disadvantage that the
oxidising agents required to prevent the formation of halogen hydrides must be
used at comparatively high temperatures and simultaneously have a decomposing
action on the dye.
The bye-products thus formed destroy the value of the commercial dye and
have therefore to be removed, so that the cost of production is increased and the
yield of dye diminished. My correspondents have discovered that the con-
version of fluorescein into cosine may be accomplished without difficulty by
electrolysis. With the aid of a suitable current of electricity the conversion may
be effected at ordinary temperatures not only in caustic alkali but also in car-
bonated alkali solutions, and the formation of discoloring bye-products is easily
avoided.
Iodine may by the same means and with equal facility to bromine be introduced
into the fluorescein molecule and the dye commercially known as erythrosine
be thus prepared.
The facile introduction of iodine is a distinctive and important feature of the
electrolytic as compared with the purely chemical process, as the latter entails
much more prolonged action and the application of heat to the mixture is
necessary to bring the reaction about. It is conceivable that the rapid intro-
duction of iodine, even at ordinary temperatures, by the electrolytic process is
due to the presence of free ions.
The process may also be applied to other fluorescein compounds, such for
instance as the halogen derivatives of fluorescein derived from the corresponding
halogenated phtalic acids. For instance by the action of bromine on tetrachloro-
fluorescein with the aid of electrolysis the commercial dye known as phloxcin
mav be manufactured.
The following may be given as an example of the manner in which the process
may be carried out;-1 kilo fluorescein is dissolved in 30 kilos water containing
1 kilo. carbonate of soda in solution and 1 kilo. bromine stirred in.
This solution is submitted to electrolysis in a vessel provided with diaphragms,

page_text: the cathode employed being preferably iron plate or iron gauze and the anode
preferably platinum gauze. A current of two or three amperes may be employed,
whilst the liquid is maintained in circulation by suitable contrivances. According
to the length of the operation shades ranging from orange yellow to bluish red
may be obtained. The current is cut off when the desired shade has been attained
and the liquid worked up in the customary manner for eosin, which usually is fit
for commercial use without further purification.
Dated this 10th day of February 1899
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents..
Improvements in the Preparation of Eosin and other Halogen
Derivatives of the Fluorescein Group.
A communication from abroad of LA SOCIÉTÉ CHIMIQUE DES USINES DU RHÔNE,
anciennement GILLIARD, P. MONNET ET CARTIER, of Lyons, France,
Manufacturers.
I, GEORGE BELOE Ellis, of the Firm of J. C. Mewburn & Ellis, of 55 and 56,
Chancery Lane, in the County of London, Chartered Patent Agents, do hereby
declare the nature of this invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
This invention relates to the preparation of eosin and other halogen derivatives
of the fluorescein group. According to this invention an electric current is
employed in the preparation.
The methods hitherto employed for the introduction of halogens into compounds
of the fluorescein group suffer more or less from the disadvantage that the
oxidising agent required to prevent the formation of halogen hydrides must be
used at comparatively high temperatures and simultaneously have a decomposing
action on the dve.
The bye-products thus formed destroy the value of the commercial dye and
have therefore to be removed, so that the cost of production is increased and the
yield of dye diminished. My correspondents have discovered that the con-
version of fluorescein into eosin may be accomplished without difficulty by
electrolysis. With the aid of a suitable current of electricity the conversion may
be effected at ordinary temperatures not only in caustic alkali but also in car-
bonated alkali solutions, and the formation of discoloring bye-products is easily
avoided.
Iodine may by the same means and with equal facility to bromine be introduced
into the fluorescein molecule and the dye commercially known as erythrosine
be thus prepared.
The facile introduction of iodine is a distinctive and important feature of the
electrolytic as compared with the purely chemical process, as the latter entails
much more prolonged action and the application of heat to the mixture is
necessary to bring the reaction about. It is conceivable that the rapid intro-
duction of iodine, even at ordinary temperatures by the electrolytic process is
due to the presence of free ions.
The process may also be applied to other fluorescein compounds, such for
instance as the halogen derivatives of fluorescein derived from the corresponding
halogenated phtalic acids. For instance by the action of bromine on tetrachloro-

page_text: fluorescein with the aid of electrolysis the commercial dye known as phloxin
may be manufactured.
The following may be given as an example of the manner in which the process
may be carried out:-1 kilo. fluorescein dissolved in 30 kilos. water containing
1 kilo. carbonate of soda in solution and 1 kilo. bromine stirred in.
This solution is submitted to electrolysis in a vessel provided with diaphragms,
the cathode employed being preferably iron plate or iron gauze immersed in a
dilute solution of caustic or carbonate of soda and the anode preferably platinum
gauze. A current of two or three amperes per square decimetre may be employed,
whilst the liquid is maintained in circulation by suitable contrivances. According
to the length of the operation shades ranging from orange yellow to bluish red
may be obtained. The current is cut off when the desired shade has been attained
and the liquid worked up in the customary manner for eosin, which usually is fit
for commercial use without further purification.
Having now particularly described and ascertained the nature of the said
invention, as communicated to me, and in what manner the same is to be per-
formed, I declare that what I claim is:
The manufacture of coloring matters of the eosin group by passing an electric
current substantially in the manner described through solutions of fluorescein or
substituted fluoresceins dissolved in alkaline solutions in presence of bromine
or iodine.
Dated this ath d
1
1000
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.