United States Patent Office
Patented Dec. 4, 1973
ELECTROCHEMICAL DETECTION CELL Harry G. Oswin, Chauncey, and Keith F. Blurton, Ossining, N.Y., assignors to Energetics Science Inc., New York, N.Y.
Filed Nov. 10,1970, Ser. No. 88,267 Int. CI. GOln 27/46' U.S. CI. 204—195 R 10 Claims
ABSTRACT OF THE DISCLOSURE
An electrochemical cell comprising an anode, a cathode and a reference electrode operating in an aqueous electrolyte is utilized for detection of noxious gases in air. The gas is oxidized at the anode and detection thereof occurs as a result of the current generated by the reaction. A fixed potential difference is maintained between the anode and the reference electrode to avoid generation of undesired current from reactions involving an oxygen-water redox couple within the cell which would invalidate anode-cathode current for gas detection purposes. The fixed potential is chosen from within the range of about 0.9 to 1.5 volts.
BACKGROUND OF THE INVENTION
Field of the invention
The present invention relates to electrochemical cells, and particularly to the structure and arrangement of a cell especially suitable for detection and measurement of noxious gases in the atmosphere.
Discussion of the prior art
In recent times, great awareness has developed regarding the dangers of air pollution, particularly in urban or industrialized areas. As the level of noxious elements in the atmosphere increases, a greater need arises for equipment to detect and measure the quantity of such elements so that their presence in the atmospheres can be reduced or eliminated. In order to meet needs arising in connection with pollution control, extensive activity has been devoted to development and production of equipment useful in solving this problem. For the successful development of such equipment, primary consideration must be accorded to the requirements of commercial and operational feasibility. Although systems may exist which may be considered functionally successful, actual utilization in practical applications has quite often been thwarted due to the cost or complexity of such equipment. Therefore, in many cases where beneficial reduction of air pollution has been an important desideratum, its achievement has been rendered impractical by the inordinately complex or costly aspects of the means proposed therefor.
Accordingly, there exists an urgent present need for air pollution control equipment which is both effective in operation and which can be practically utilized in widespread commercial applications without incurrence of excessive cost. This requirement exists in connection with equipment for the detection and measurement for polluting materials, as well as for equipment whereby the quantities of such materials may be controlled or reduced.
The general criteria applied to measuring and testing equipment such as the cell of the present invention include requisites for portability, non-prohibitive cost and accuracy in measuring the quantity of the gas detected. In the prior art, it has been found difficult to simultaneously fulfill all of these requirements. Increasing the accuracy of measuring equipment has inherently involved an increase in either the size or the complexity of such equipment thereby disadvantageously affecting either
cost or portability or both. Quite often, problems related to the simultaneous provision of these features have been decisive in obstructing the practical development and utilization of particular detection apparatus.
g It is, therefore, considered of significant importance and a valuable contribution to the art of pollution control equipment to provide detection apparatus capable of accurately measuring gas quantity which is also of a relatively convenient size enabling portability, and which
10 does not involve prohibitive cost for its manufacture and practical utilization.
SUMMARY OF THE INVENTION
Briefly, the present invention may be described as an lg electrochemical cell for the detection of noxious gases, said cell comprising an anode, a cathode, an aqueous electrolyte, means for exposing the anode to a substance to be detected, means defining a reference potential, and means for maintaining a fixed potential upon said anode 2q relative to said reference potential, said fixed relative potential being from within a range wherein an oxygenwater redox couple within the cell is ineffective to generate current at a level which is discernible relative to the level of current produced therein by a reaction involving the substance to be detected.
By a more specific aspect of the invention, the fixed relative potential is chosen from within the range of about 0.9 to 1.5 volts anodic relative to the hydrogen couple as a zero base.
30 By another specific aspect of the invention, the cell is constructed to comprise an anode chamber defining a labyrinthine path through which the air is passed to appropriately expose to the anode the substance to be detected. Alternatively, the anode chamber may comprise 3g propeller means for effecting such appropriate exposure.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention may be had by reference to the following detailed description 40 of the preferred embodiments thereof taken in connection with the accompanying drawings wherein:
FIG. 1 is a view in perspective of a cell embodying the principles of the present invention;
FIG. 2 is a sectional view taken along the line 2—2 of FIG. 1;
FIG. 3 is a side elevation partially broken away of an interior portion of the cell of FIG. 1 depicting in better detail the anode chamber of the cell;
FIG. 4 is a side elevation partially broken away showing the cathode structure of the cell which, in FIG. 1, is out of view on the back side thereof;
FIG. 5 is a partial view in perspective of an alternative embodiment for the anode chamber of the cell of the invention;
rp FIG. 6 is a chart derived from the Electromotive Series Jd of Elements indicating for exemplary redox couples theoretical relative electrode potentials determining whether a couple will undergo an oxidation or a reduction reaction;
FIG. 7 is a curve depicting the nature of the relation60 ship between current which may be developed in a cell due to an oxygen-water redox couple and applied elec■ trode potential; and
FIG. 8 is a schematic diagram of a potentiostat circuit for controlling operation of the cell and particularly 65 as applied in maintaining a fixed relative potential difference between the cell anode and a reference electrode.
DETAILED DESCRIPTION OF A PREFERRED
70 Referring now in detail to the drawings, there is shown in FIG. 1 an electrochemical detection cell embodying the principles of the present invention which comprises an