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Abstract

An electro-chemical cell for quantitatively detecting an acidic or an alkaline gas, e.g. carbon dioxide, includes a sensing electrode 9 which is connected to a top cap 12 by a contact strip 8 and is accessible to the gas to be tested through a hole 13. The electrode 9 comprises an electro-chemical couple whose potential is pH-dependent (e.g. silver/silver oxide for carbon dioxide) the active material being supported by a nickel gauze to give good current collection. A counter electrode 2 without significant gas access is immersed in an electrolyte 3 whose pH is such that it will change following adsorption of the gas being tested for. A wicking separator 7 ensures an electrolytic path between the two electrodes. The components are contained within a metal can 1, the top cap 12 being held by folding over the rim 5. An insulating grommet 6 is fitted between the two electrodes. When using silver/silver oxide for the sensing electrode 9, the counter electrode may be of the same material and the electrolyte may be potassium carbonate. The current flowing between the electrodes is a measure of the concentration of gas being detected. A reference electrode 14 may also be included.

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First Claim