DE2549216A1 - GALVANIC CELL - Google Patents

Description

SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ B.V. The Hague, Netherlands

"Galvanic cell according to patent (patent application

P 24 02 436.O) "

Priority: November 5, 1974 - Great Britain - No. 47797/74

The invention relates to a galvanic cell with a zinc electrode, which is in contact with an aqueous alkaline electrolyte, according to patent .... (patent application P 24 02 436.0), in the electrolyte a 2.00 to 4.75 mol. liter "potassium hydroxide and 9 to 36 gramions. liters "containing silicate ions Solution is used.

In the galvanic cell described in the main application, a relatively high speed of the water can occur.

relative

s transfers come through the cathode. This cell can be used above / humidity levels of 30 to 80%. Within this range, conventional electrolytes, ie, 7 to 8 mole liters of "1 potassium hydroxide-containing electrolytes, tend not to lose or attract excessive amounts of water. In contrast, the 2.00 to 4.75 mole liters of" ¹ potassium hydroxide tend to do so

609820/0776

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and 9 to 36 gramions. liters "containing silicate ions, in The electrolytes used in the cells described above lead to a loss of water over the humidity range described above,

Because the range of potassium hydroxide concentration over which the beneficial effect of the above-described electrolytes is observed is very narrow, i.e. from 2.00 to 4.75 mol. liters ~, a loss of water can lead to the System leaves the best possible work area.

It is therefore desirable to provide a galvanic cell with an electrolyte in which the above Problem does not occur.

The invention accordingly relates to a galvanic cell with a zinc electrode, which with an aqueous alkaline electrolyte is in contact, in which the electrolyte is a 2.00 to 4.75 mol. liter "potassium hydroxide" and 9 to 36 gram ion. liter "silicate ions containing solution is used, according to patent

(Patent application P 24 02 436.0), which is characterized by that the electrolyte additionally contains an inert water-soluble additive to reduce its vapor pressure.

In the present description, inert additive is understood to mean an additive which has no electrochemical effect affects the required operation of the system in which the electrolyte is used.

The electrolyte preferably contains potassium hydroxide in one concentration from 3.00 to 4.50 Mol.Liter "and the silicate ions

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in a concentration of preferably 27 to 36 gram ions. ^{liters "1.}

Organic and inorganic additives can be used as inert additives are used, but preference is given to inorganic additives and, in particular, inorganic salts, such as alkali metal salts and, for example, their halides such as potassium fluoride are used. Organic compounds that are themselves one

low vapor pressure, such as ethylene glycol, can also be used. The inert additive is preferably used in concentrations of from 2.00 to 500 mol. Liters Mixtures of inert additives can also be used.

The table below shows the effect of adding various Amounts of potassium fluoride to the electrolytes. It can be seen from the table that electrolytes preferred according to the invention have vapor pressures which are approximately those of 8.00 Mol.Liter "potassium hydroxide-containing electrolytes correspond.

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Tabel

Potassium hydroxide
concentration,
Mole liter " ¹ Potassium fluoride
concentration,
Mol.Liter " ^l Vapor pressure at
298 ⁰ K, mmHg 3.0 no 22.9 3.0 1.0 20.4 3.0 2.0 19.5 3.0 3.0 18.2 3.0 4.0 15.9 3.0 5, .O 13.8 8.0 no 15.1 no no 23.7

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Claims (9)

Claims 1. Galvanic cell with a zinc electrode which is in contact with an aqueous alkaline electrolyte, in which a solution containing 2.00 to 4.75 mol. Liters " ¹ potassium hydroxide and 9 to 36 gram ions. Liters" of silicate ions is used as the electrolyte, according to patent .... (patent application P 24 02 436.0), characterized in that the electrolyte additionally contains an inert water-soluble additive to reduce its vapor pressure. 2. Galvanic cell according to claim 1, characterized in that the electrolyte contains 3.00 to 4.50 Mol.Liter ' ¹ potassium hydroxide. y. Galvanic cell according to Claim 1 or 2, characterized in that the electrolyte contains 27 to 36 gram ions. Liters "of silicate ions. 4. Galvanic cell according to claim 1 to 3 * characterized in that that the electrolyte contains an inorganic salt as an inert additive. 5 · Galvanic cell according to claim 4, characterized in that that the electrolyte contains an alkali metal salt as the inorganic salt. 6. Galvanic cell according to claim 5, characterized in that that the electrolyte contains an alkali metal halide as the alkali metal salt. S098207077S 7. Galvanic cell according to claim 6, characterized in that that the electrolyte contains a fluoride as an alkali metal halide. 8. Galvanic cell according to claim 7> characterized in that the electrolyte contains potassium fluoride as the alkali metal fluoride, 9. Galvanic cell according to claim 1 to 8, characterized in that the electrolyte contains the inert additive in an amount of 2.00 to 5.00 Mol.Liter " ¹ . 609820/0776