Improved Exciting Fluid for Galvanic Zinc Carbon Batteries, and Method of Recovering Useful Products from the Spent Fluids of such Batteries.
Year: 1891

page_text: Date of Application, 12th Nov., 1891--Accepted, 23rd Apr., 1892
COMPLETE SPECIFICATION.
Improved Exciting Fluid for Galvanic Zinc Carbon Batteries, and
Method of Recovering Useful Products from the Spent Fluids of
such Batteries.
I, MAX MÜTHEL of 94, Invalidenstrasse, Berlin in the German Empire,
Electrician, do hereby declare the nature of this invention and the manner
in which the same is to be performed to be particularly described and ascertained
in and by the following statement :-
My invention relates to a novel chromic acid exciting fluid for galvanic batteries,
characterized by the employment of bisulphate of ammonia and which in conse-
quence of its composition renders it possible to regain the chrome and the zinc
from the spent fluid. Exciting fluids for galvanic elements composed of chromic
acid Cr O, and potassium or sodium sulphate are known.
3
Whereas however these alkaline salts, which do not evaporate under heat when
used in combination with chromic acid, do not permit a regeneration of the spent
fluid. The employment of the bisulphate of ammonia according to my invention
in combination with free chromic acid possesses the advantage that the spent fluid
can be decomposed in order to regain the valuable chrome and zinc salts.
My improved fluid contains in spent condition sulphate of zine and chrome alum
of ammonia which can be submitted to the following process.
When the zinc has
been electrolytically precipitated out of the fluid, which is held neutral during the
electrolysis by means of ammonia by employing carbon or lead anodes, the fluid.
containing chrome alum of ammonia and bisulphate of ammonia is evaporated, and
the deposit heated to glow heat calcined whereby the chrome alum of ammonia is
decomposed, chromic oxide remaining behind as a valuable bye-product.
The ammonia escaping amongst other matter from the sulphate of ammonia
during the heating can be used for neutralising the chrome lye in the subsequent
electrolysis.
The mixture in question consisting, in contradistinction to the chrome salts, of
free chromic acid in combination with bisulphate of ammonia has never to my
knowledge been used in galvanic batteries for the purpose as aforementioned.
A modified process for treating the spent fluid of galvanic batteries of the kind
aforementioned so as to regain the valuable parts of the same and specially the
zinc, consists in precipitating the chrome and zinc contained in the spent fluid in
the form of phosphoric acid compounds by adding phosphoric acid or the compounds
of the same to the chromic acid solution, that is, the phosphoric acid, the chroine
and also the zinc is regained in such form that they represent valuable products.
If at the outset free phosphoric acid or acid phosphates be added to the
bisulphate of ammonia and chromic acid solution, all the chrome and zinc can be
readily precipitated out of the spent fluid, as phosphoric acid compounds by
neutralising the fluid by means of ammonia. The above-named exciting fluid for
charging galvanic batteries consisting of chromic acid and bisulphate of ammonia
can in order to produce a greater duration of the exciting properties of the fluid
be provided with an addition of chloride of iron.
The depolarising action which is facilitated by the addition of the chloride of
iron is evidently derived from the chromic acid, for so long as free chromic acid
is present, the protoxide of iron will under the action of the chromic acid in com-
bination with the liberated hydrochloric-acid be reconverted into chloride of iron.
The chloride of iron will after the chromic acid has become exhausted maintain
the depolarisation for a time and leave protoxide of iron as residue.
Many attempts have been made to employ chloride of iron in exciting fluids but,
up to now without success.

page_text: The proportions used are about as follows. 10 parts raw chromic acid, 30 parts
bisulphate of ammonia, 1 part phosphate of sodium, and if desired 1 part chloride
of iron. In place of sodium, phosphate of potassium can be used.
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. In exciting fluids for galvanic batteries, the application of free chromic acid
in combination with bisulphate of ammonia substantially as described.
2. In exciting fluids consisting of free chromic acid and bisulphate of ammonia
the addition of phosphoric acid or a salt containing phosphoric acid for regaining
the salts of chrome and zinc substantially as described.
3. The addition of protoxide of iron to the fluid claimed in Claim 1 in order to
prolong the exciting action of the said fluid substantially as described.
Dated this 12th day of November 1891.
FREDERIC PRINCE,
1, Quality Court, Chancery Lane, London, Agent for Applicant.