Year: 1886

page_text: Date of Application, 21st Apr., 1886.
Complete Left, 21st Jan., 1887.
Complete Accepted, 19th Apr., 1887.
I DESMOND GERALD FITZ-GERALD, of 6 Akerman Road, Brixton, in the County
of Surrey, Electrician, do hereby declare the nature of this invention to be as
follows:-
My Invention consists in the electrolytic regeneration or production of chromic acid
from a solution of chromic acid, or an acid solution of a chromate, or bichromate salt
which has been exhausted in the production of oxygen or chlorine, as for example in
the working of voltaic batteries and in bleaching operations.
•
In batteries in which a solution of chromic acid or an acid solution of a chromate or
bichromate salt is used as the depolarizing agent, a salt of chromium is ordinarily
formed by the reduction of the chromic acid used or set free in the solution, and when
the whole of the chromic acid has become so reduced, the exciting or depolarizing
solution is exhausted and useless for the purpose in view.
Hitherto the chromium salt has either been wasted, or has been utilized by purely
chemical means for various purposes not connected with the working of batteries.
But according to my invention the chromium salt is decomposed and oxidised by
means of electrolysis effected by the aid of a dynamo-machine or other economical
source of electrical energy; the chromic acid thus set free being again utilizable for
the working of batteries. At the same time a portion at least of the zinc sulphate
which the exhausting exciting fluid ordinarily holds in solution becomes separated
from it by the electrolytic action of the current and may be reduced to the metallic
state or otherwise utilized.
In carrying out my Invention I use preferably an anode of lead which is immersed
in the solution (ordinarily containing sulphate of chromium and sulphate of zinc) to
But other
be electrolytically decomposed for the production of chromic acid.
conductors such as platinum or carbon which are not readily effected by the solution
may be employed for the anode. A sheet of lead or of zine or almost any other conductor
may be employed for the cathode which is ordinarily immersed in an acid solution
containing sulphate of zinc, such as is obtained by working the present process of

page_text: regeneration. Or, a solution of ammonia-alum in which oxide of zinc has been
dissolved may be employed at the cathode. A porous diaphragm or vessel is employed
to separate the solutions in the anode and cathode compartments. When the dark
colored solution to be converted has obtained a bright red color the electrolytic
decomposition effected in the anode compartment is complete. The zinc reduced in
the cathode compartment may be subjected to fusion by which process the oxide of
chromium deposited at the cathode is separated from the reduced metal.
In order to obviate the inconvenience of transporting large quantities of exhausted
solution I run the latter into a tank containing lime, calcined magnesite, or other
suitable substance that will precipitate the oxides of chromium and zinc. When the
precipitation is complete, the supernatant solutions may be run off and the solid residue
is then transported to the works where the process of re-generation is carried on. The
precipitated oxides are then re-dissolved, either together or separately; the chromic
oxide being afterwards converted into chromic acid, and the zinc being reduced to the
metallic form, as above described.
D. G. FITZ-GERALD.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: Battery and other Solutions.
I. DESMOND GERALD FITZ-GERALD of 6 Akerman Road Brixton in the County of
Surrey Electrician 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 Invention consists in the electrolytic regeneration or production of chromic
acid in solution, from the chromium salt resulting from the use of a solution of chromic
acid (or an acid solution of a chromate or bichromate salt) for the production of
oxygen or chlorine, as, for example, in the working of voltaic batteries and in bleaching
operations.
In batteries in which a solution of chromic acid or an acid solution of a chromate
or bichromate salt is used as the depolarizing agent, a salt of chromium is ordinarily
formed by the reduction of the chromic acid used or set free in the solution, and
when the whole of the chromic acid has become so reduced, the exciting or
depolarizing solution is exhausted and useless for the purpose in view.
Hitherto the chromium salt has either been wasted, or has been utilized by purely
chemical means. But, according to my Invention, the chromium salt is decomposed
and oxidized by means of electrolysis effected by the aid of a dynamo machine or
other economical source of electrical energy, the chromic acid thus set free being
again utilizable for the working of batteries or. to effect the liberation of chlorine..
At the same time, a portion at least, of the zinc sulphate, which the exhausted'
exciting fluid of a voltaic battery, ordinarily holds in solution, becomes separated
from it by the electrolytic action of the current and may be reduced to the metallic
state, or otherwise utilized.
In carrying out my Invention, I use, preferably an anode of lead which is
immersed in the solution (ordinarily containing chromium and zinc sulphates, or
chromium chloride, as the case may be) to be electrolytically decomposed for the
production of chromic acid. But other conductors, such as platinum or carbon,
which are not readily affected by the solution, may be employed for the anode. A
sheet of lead or of zinc (or almost any other conductor) may be employed for the
cathode which is ordinarily immersed in an acid solution containing sulphate of zinc
such as is obtained by working the present process of regeneration. Or, a solution
of ammonia-alum in which oxide of zinc has been dissolved may be employed at the
cathode. A porous diaphragm or vessel is employed to separate the solutions in the
anode and cathode compartments.
When the dark colored solution to be converted has acquired a bright red color
the electrolytic decomposition, effected in the anode compartment, is complete and
the whole of the chromium salt originally in solution has been decomposed with
liberation of its acid and oxidation of its oxide of chromium into chromic acid.

page_text: The zinc reduced in the cathode compartment may be subjected to fusion by which
process the oxide of chromium deposited at the cathode is separated from the reduced
metal.
The
In order to obviate the inconvenience of transporting large quantities of exhausted
solution, I run the latter into a tank containing sufficient lime, calcined magnesite,
or other base, to precipitate the oxides of chromium and zinc. When the precipitation
is complete, the supernatant solutions may be run off and the solid residue is then
transported to the works where the process of regeneration is carried on.
precipitated oxides are then dissolved, either together by means of a dilute minera!
acid, or separately by treatment first with ammonia or a boiling solution of a fixed
alkali to dissolve the oxide of zinc, and afterwards with dilute acid or a cold solution
of fixed alkali to dissolve the oxide of chromium. The chromic oxide of the chromium
salt so formed is afterwards oxidized into chromic acid electrolytically and the zine
reduced to the metallic form, as above described.
Having now particularly described and ascertained the nature of the said Invention,
and in what manner the same is to be performed, I declare that what I claim is ;-
1. The herein described process of electrolytically regenerating or producing chromic
acid in solution, from the chromium salt formed by the reduction of this acid when it
is used for the generation of oxygen, as in voltaic batteries, or for the production of
chlorine for bleaching and other purposes.
2. The herein described process of regenerating or producing chromic acid in
solution, from the exhausted or reduced solution of this acid when it has been employed
for the generation of oxygen or of chlorine; which process consists in treating the
solution with a base that will precipitate oxide of chromium (together with oxigle of
zine when this is present) re-dissolving the oxide of chromium, and converting into
chromic acid, by electrolysis, the salt of chromium thus obtained.
D. G. FITZ-GERALD.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.