IMPROVEMENTS IN ELECTROLYTES
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
We, STEPHEN HENRY EMMENS of 8 Argyll St. Regent St, in the County of
Middlesex Electrical Engineer, and THE UNITED PATENTS CORPORATION, LIMITED
of 27 Cheapside in the City of London do hereby declare the nature of our invention
for IMPROVEMENTS IN ELECTROLYTES to be as follows:-
:-
The object of our invention is to produce substances which when employed as
electrolytes in galvanic batteries shall give electric currents of great electromotive
force and constancy.
We carry out our invention by treating bichromate of potash with dilute sul-
phuric acid. A partial decomposition of the salt is thus effected and the super-
natant liquor contains a large proportion of chromic acid in solution. This we
decant and then we wash the residue with cold water and add such washing to the
decanted liquor. The remainder of the salt we dissolve in about seven times its
weight of sulphuric acid which causes a further quantity of chromic acid to rise to
the surface. This we skim off and add to the beforementioned liquor together with
enough sulphuric acid to form sulphate of chromium when the liquid is used in
galvanic batteries. We then add to the acid solution of the salt a fresh quantity
of bichromate of potash equal in weight to the quantity first employed and after
well stirring we allow the mass to cool and solidify. We thus obtain in the end a
fluid and a solid both of which we denominate Chromozone, and both of which form
excellent electrolytes for single or double fluid galvanic batteries the solid chromo-
zone being simply dissolved in water when required for use.
As an alternative to the aforesaid process we treat bichromate of potash with
sulphuric acid in the ordinary known method for manufacturing chromic acid and
we convert this latter into chromozone by dissolving it in water and adding sufficient
sulphuric acid to form sulphate of chromium when employed in galvanic batteries.
The mother liquor remaining after separation of the chromic acid we either mix
with nine times its volume of water and then it is ready for use as a positive
electrolyte or we add to it nitric acid or the solution of a nitrate and then it is
ready for use as a negative electrolyte.
In cases where fuming is not of importance we add either nitric acid or the
solution of a nitrate to the above described chromozone.

page_text: We STEPHEN HENRY EMMENS of 8 Argyll Street, Regent Street in the County
of Middlesex, Electrical Engineer and THE UNITED PATENTS CORPORATION LIMITED
of 27 Cheapside in the City of London do hereby declare the nature of our
invention for IMPROVEMENTS IN ELECTROLYTES and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement :—
The object of our invention is to produce substances which when employed as
electrolytes in galvanic cells shall give electric currents of great electromotive force
and constancy.
We carry out our invention by combining chromic acid with sulphuric acid in
the proportion of two equivalents of the former to three equivalents of the latter so
that sulphate of chromium may be formed when the chromic acid is reduced to the
state of sesquioxide.
We prefer to use uncombined chromic acid but as this substance is usually sold
in combination with potash or soda we ordinarily employ commercial bichromates
as our source of chromic acid. We decompose these bichromates with sulphuric
acid, and in the case of the potash salt we either crystallize out the chromic acid
by the ordinary known method or we eliminate the greater portion of the potash
by first partially decomposing the salt and decanting the chromic acid in solution,
and then (after an intermediate washing with cold water) adding to the residue
about seven times its weight of sulphuric acid, which causes the greater portion of
the remaining chromic acid to float to the surface, when it is skimmed off for use.
When the mother liquor cools a considerable quantity of sulphate of potash
crystallizes out which we remove, and we then add to the acid a quantity of
bichromate of potash equal to the weight originally treated. On again being
allowed to cool the mass solidifies. In the case of sodium bichromate we effect the
required decomposition by the addition of an equivalent of sulphuric acid and then
to the solution of chromio acid thus obtained we add three further equivalents of
sulphuric acid.
It is not necessary that the sulphuric acid used in decomposing the potassium
-bichromate shall be free. We find that by adding an equivalent of sulphate of
soda to a hot saturated solution of an equivalent of potassium bichromate we can
obtain crystallised sodium bichromate for treatment as above specified and can
thus eliminate the potash.
The solution of chromic acid compounded with sulphuric acid in any of the
abovedescribed ways we denominate Fluid Chromozone, and the solid body
-produced by the admixture of bichromate of potash with the other liquor from
the first stage in the manufacture of fluid chromozone from potassium bichromate
we denominate Solid Chromozone. The latter when dissolved in water is ready
for battery use.
Chromozone is a very active dehydrogenising agent and enables a current
having an electromotive force of over 2 volts per cell to be obtained with great
steadiness; but if the quantity of current required be in excess of one Ampère for
every 15 square inches of negative electrode surface the rapidity of dehydrogenisa-
tion is not sufficient to avoid partial polarisation. In such cases we assist the
action by employing nitric acid to feed the chromic acid with oxygen, and we find
that this nitric acid may conveniently be added in the form of a nitrate with
sufficient sulphuric acid to decompose such nitrate. The particular mixture of this
kind which we prefer to employ and which we denominate Natro-Chromozone is

page_text: composed of 1 equivalent of sodium bichromate 2 equivalents of sodium nitrate
63 equivalents of sulphuric acid and 115 equivalents of water-these proportions
being so calculated as to provide first, a complete re-supply of oxygen to the
chromic acid; secondly, enough sulphuric acid to unite with all the soda contained
in both the bichromate and the nitrate; thirdly, enough sulphuric acid to unite
with the whole of the chromium when reduced to sesquioxide; fourthly, enough
water to chemically unite with the sodium and chromium sulphates; fifthly,
enough water to keep the resulting saline solutions in a proper state of dilution;
and sixthly, an excess of sulphuric acid sufficient to maintain the electrical
conductivity of the fluid.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that what
we claim is :-
1. The combination in a galvanic cell of an electrolyte composed of an aqueous
solution of chromic acid mixed with sufficient sulphuric acid to unite with the
whole of the chromium when reduced to sesquioxide, substantially as specified.
2. The combination in a galvanic cell of an electrolyte composed of an aqueous
solution of potassium bichromate from which the greater portion of the potash has
been removed and to which has been added enough sulphuric acid to combine with
the remaining potash and with the whole of the chromium when reduced to
sesquioxide, substantially as specified.
3. The combination in a galvanic cell of an electrolyte composed of an aqueous
solution of sodium bichromate and nitrate mixed with sulphuric acid, substantially
as specified.
4. The process of decomposing potassium bichromate by adding sodium sulphate
to a solution of the bichromate, substantially as specified.
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