Abstract: A system and method of detecting the end of useful life in a gas sensor cell having a cathode, anode, one of which is consumable, and an electrolyte, and a circuit for controlling the flow of gas to the cell and a sensing resistor and circuit connected to said cathode and said anode, the consumable electrode is provided in the form of a plurality of discrete elements which are sequentially connected in circuit with the other electrode, sensing resistor and circuit. A drop in current between respective ones of the consumable electrode is an indication of the approach of the end of the useful life of the gas sensor.

Abstract: An oxygen sensor constructed as a coulometric sensor and capable of detecting oxygen concentrations in the range of 1% or greater concentrations. The coulometric sensor utilizes a gas flow path which has a predetermined section constructed with oxygen-permeable tubing, wherein a portion of the oxygen flowing through the gas flow path will permeate into the sensor to generate an electric current flow indicative of the permeating oxygen level. The length of the tubing section which is constructed from oxygen-permeable material maybe selectively adjusted to control the relative attenuation of oxygen flow through the sensor.

Abstract: An electrochemical sensor having at least two electrodes that communicate with a liquid measurement cell electrolyte and a housing that encloses the electrodes and the electrolyte. The surfaces of the electrodes facing the electrolyte bridge web connecting the electrodes are covered with a semipermeable membrane.

Abstract: An electrochemical gas sensor comprises sensing and counter electrodes (1,2). A conduit (15) permits access of gas to the sensing electrode (1). An electrolyte reservoir (23). A porous, block-like body (24) is positioned in the reservoir (23) for conveying electrolyte to the sensing and counter electrodes and at least partly supporting other components of the sensor.

Abstract: A polarographic electrochemical cell for the measurement of oxygen in ppb. The cathode in the system is a non-depleting carbon polytetrafluoroethylene electrode catalytically specific for oxygen reduction. The anode is a composite nickel matrix. The reaction at the anode is an electrochemical oxidation reaction but there are no soluble byproducts that contaminate the electrode. The reaction at the anode is a simple oxidation, state-of-change of the nickel in the nickel composite matrix.

Abstract: An electrochemical sensor for fluid media with at least two electrodes, which are in contact with one another via an electrolyte and are accommodated in a housing. Many different sensor variants are attainable with a few, standardized components. The housing (1) includes a plurality of modules (4a, 4b; 4c-4m), which are placed next to one another, are designed as hollow bodies, and are connected to one another, wherein at least two lateral surfaces (9) of each module (4a-4m) are suitable for connection to additional modules (4a-4m), and at least two of the modules (4a, 4b; 4c-4m) accommodate one electrode (2, 3) each, and the hollow space (16) enclosed by the modules (4a, 4b; 4c-4m) is delimited from the environment by the two electrodes (2, 3), on the one hand, and by a partial area (17) each of the inner wall (5) of the modules (4a, 4b; 4c-4m), and is provided for accommodating the electrolyte (18).

Abstract: An apparatus for the quantitative determination of chlorine in a fluid environment, comprising a flat ion exchange membrane-based sensor which utilizes a layer of an electrochemically inert hydrated salt or combination of such salts to provide water for the reduction of such chlorine to chloride ion, and the detection of chlorine by such reduction.

Abstract: A compact electrochemical gas sensor for detecting toxic gases is described which utilizes a fluted electrically-conducting feedthrough for making the electrical connection from outside the sensor with each electrode inside the sensor. Utilization of the fluted electrically-conducting feedthroughs significantly reduces the number of parts needed to make the sensor as well as reduces the likelihood of electrolyte leakage from the sensor. Additionally, the electrochemical toxic gas sensor may use a gas permeable membrane instead of a gas porous membrane.

Abstract: An electrochemical gas sensor for detecting gaseous components in the environment has a diffusion membrane, a measuring electrode, a counterelectrode, and, if desired, a reference electrode, pressed together in a disk stack, which are accommodated in a pot-shaped cover, which in turn is beaded around the sealing edge (6) of a housing pot (1). A compression spring (21) in the housing pot (1) presses a wick disk (20) against the measuring electrode (12), so that a constant and pressurized, intimate and sealed positioning of the disk stack is guaranteed. It is achieved as a result that no additional contact leads from the electrodes to the outer space of the sensor to the measuring and evaluating unit are needed, so that leakage-free sealing of the sensor to the outside is possible, and that a constantly stable, reproducible measured signal is obtained because of the defined and narrow electrolyte film on the surface of the measuring electrode.

Abstract: An oxygen sensor for measuring oxygen in the ppb range. The sensor comprises an electrochemical cell. The oxygen is metered to the cathode based on gaseous phase diffusion to provide a measurement proportional to volumetric concentration. Hydrogen is metered to the anode in an amount in excess of the oxygen being reduced at the cathode. A current is generated which is linear to the volumetric concentration of the oxygen in the sample gas. The concentration of the oxygen is measured based on the current generated.

Abstract: An analyzer for detecting a selected chemical (such as oxygen) in a process fluid includes a plurality of electrodes that are separated from the fluid by a membrane that is permeable to the selected chemical, each of the electrodes when energized producing a signal in response to the selected chemical in the fluid. The selected chemical level in the process fluid is determined based on the signal produced by a first one of the electrodes, and the determined level is used with the signal produced by a second one of the electrodes to detect whether the membrane has become faulty (e.g., fouled by materials in the process fluid).

Abstract: An improved perfluorinated, ion-exchange polymer, either in the form of a membrane or a thin film useful as the electrolyte in chemical sensors. The polymer is treated with an acid, such as boric acid or a mixture of boric acid and phosphoric acid, to maintain the ionic conductivity of the polymer to approximately 180 degrees Centigrade. The improved polymer electrolyte is utilized to sense moisture by a two electrode structure with the electrodes arranged in interdigital fashion and the electrolyte film cast over the electrodes. The electrolyte is included in a 3 electrode sensor for sensing various types of gases.

Abstract: A sensor for gaseous and vaporous species is disclosed. The sensor comprises an electrically insulated substrate which contains small pores passing completely through it. Electrodes consisting of metallic or semiconductor material are deposited onto the top surface of the substrate. In a first embodiment of the invention, an electrolyte is placed on the top surface of the substrate in such a manner as to create a gas or vapor permeable electrolyte layer on top of the electrodes. In a second embodiment of the invention, the electrolyte is applied to the bottom surface of the substrate and seeps up through the porous holes of the substrate until it makes contact with the electrodes. Both embodiments result in a gas sensor with a response time dependent upon the gas flow rate rather than the time required for the gas to be dissolved in the electrolyte layer and be detected.

Abstract: An electrochemical gas sensor cell is provided, the use of which permits quantitative measurement of volatile gas contaminants in an atmosphere being monitored. The cell comprises at least a first sensor electrode and a second counter electrode, on either side of an ion conductive electrolyte which may be immobilized in a matrix. The electrolyte may also be a solid electrolyte or a polymer electrolyte. The sensing electrode has a high surface area catalyst dispersed on a porous substrate, and is mounted in such a manner as to be exposed to the atmosphere which is to be sensed for gaseous contaminants, with the counter electrode being isolated from any exposure to that atmosphere. Generally, the electrodes are mounted in electrically conductive frames, sandwiching a third non-conductive frame member in which the ion conductive electrolyte is substantially located. The conductive frames may comprise electronically conductive materials such as conductive polymers, ceramics, nitrides, oxides and graphites.

Abstract: The device for the simultaneous detection of dissimilar gas components contains a number of electrochemical, three-electrode measuring cells with a common electrolyte, that are formed from a number of working electrodes with a common counter-electrode and a common reference electrode. Measured values are generated with the aid of a potentiostatic evaluation circuit that also adjusts and sets the potentials at the working electrodes. The current signals correlated with the gas concentrations to be measured are displayed with the aid of current-measuring instruments 11.sub.1 . . . 11.sub.n in the lines to the working electrodes 5.sub.1 . . . 5.sub.n. At the same time it is important that all three-electrode measuring cells have a common counter-electrode 3 and a common reference electrode 4, and that the potentiostatic evaluation circuit 6 contains control loops 7.sub.1 . . . 7.sub.n which maintain the potentials of the working electrodes 5.sub.1 . . . 5.sub.

Abstract: A method and apparatus for measuring the formaldehyde emission of composite wood products bonded with urea-formaldehyde adhesives employing the combination of a small sample chamber and an electrochemical sensor.

Abstract: An electrochemical sensor for detecting gas includes stacked reference, counter and sensing electrodes within a body and having a quantity of a liquid electrolyte in an electrolyte chamber therein. A support is provided for holding the electrodes and mats in contact with each other and at an inner end of a cavity within the sensor. A gas passage, such as a diffusion limiter, is provided through the sensor body and permits gas to reach the sensing electrode. The reference electrode is formed in a wraparound structure, with the reference electrode provided with a plurality of integral extensions which extend around the support and the counter electrode and into contact with the liquid electrolyte, thereby providing a large reference electrode fitted into a small body.

Abstract: Schottky diodes and gas sensors include a diamond layer having a Schottky contact thereon and an ohmic contact thereon, wherein the diamond layer includes a highly doped region adjacent the ohmic contact to provide a low resistance ohmic contact. Dramatically reduced frequency dependence of the capacitance/voltage characteristic of Schottky diodes and gas sensors formed thereby, compared to Schottky diodes and gas sensors which do not include the highly doped region adjacent the ohmic contact, is provided. The highly doped region is preferably boron doped at a concentration of at least 10.sup.20 atoms per cubic centimeter to form an ohmic contact with a contact resistance of less than 10.sup.-3 .OMEGA.-cm.sup.2. The ohmic contact is preferably a back contact on the face of the diamond layer opposite the Schottky contact.

Abstract: The invention is directed to a measuring sensor for detecting gaseous components which operates in the diffusion limit current region. The measuring sensor includes a support body and has an electrolyte chamber partitioned by a diffusion membrane from the ambient containing the gaseous components. The measuring electrode of the measuring sensor is improved so that a simpler manipulation for covering the electrolyte chamber with a membrane is possible without endangering the mechanical stability of the membrane. During operation, the detection operation is intended to take place completely at that electrode surface which is in direct electrochemical exchange communication with the electrolyte supply. For this purpose, the coating is configured as an adherent layer to the support body so that it forms an impermeable adherence region in the lateral direction between coating and support body.

Abstract: An oxygen sensor for measuring oxygen in the ppb range. The sensor comprises an electrochemical cell. The oxygen is metered to the cathode based on gaseous phase diffusion to provide a measurement proportional to volumetric concentration. Hydrogen is metered to the anode in an amount in excess of the oxygen being reduced at the cathode. A current is generated which is linear to the volumetric concentration of the oxygen in the sample gas. The concentration of the oxygen is measured based on current generated.

Abstract: An electrochemical carbon monoxide detecting method and apparatus (10, 46) is disclosed which can detect carbon monoxide levels as low as about 500 ppm and which has excellent selectivity and a linear response over a broad range of carbon monoxide concentrations. The apparatus (10, 46) employs an electrical cell assembly (12, 54) having an electrolyte (20, 60) containing hydrated Cu(II) ions therein; upon creation of a constant magnitude potential difference between the cell electrodes (22, 24) ranging from about +0.03-+0.15 V, the Cu(II) ions are reduced to Cu(I) ions, and the latter react with carbon monoxide to form Cu(I)-carbonyl complexes. Detection of an electrical parameter indicative of the Cu(II)-Cu(I) reduction permits quantitative carbon monoxide determinations. Preferably, the detecting apparatus (14) is amperometric, employing a potentiostat (28) and output device (38). Alternately, detection can be accomplished potentiometrically.

Abstract: An air/fuel ratio sensor with a sensing element having an electrochemical oxygen pumping cell including a first oxygen ion-conductive solid electrolyte body, and a first and a second electrode formed on the first solid electrolyte body, an electrochemical oxygen sensing cell including a second oxygen ion-conductive solid electrolyte body, and a third and a fourth electrode formed on the second solid electrolyte body, the second and third electrodes being exposed to exhaust gases which are produced as a result of combustion of an air-fuel mixture and which are introduced into the sensing element, under a predetermined diffusion resistance.

Abstract: An improved oxygen sensing electrode assembly is provided with first and second electrodes mounted within a cavity of a housing substrate. An oxygen permeable diaphragm closes the cavity and contains an appropriate electrolyte solution. A third electrode is mounted in the cavity, while a fourth electrode is mounted on the exterior of the housing. The third and fourth electrodes can be activated to monitor the condition of the electrolyte whereby the operability of the electrode assembly can be verified during an oxygen sensing measurement.

Abstract: An oxygen sensor or cell for measuring the oxygen content of a specimen includes a body with a chamber that houses an electrochemically active anode and an electrochemically active cathode. A chemically inert, electrically inactive porous material is disposed between and in contact with the anode and cathode. An anode connector is in contact with the anode and a cathode connector is in contact with the cathode. An electrolytic solution of potassium hydroxide and a dissolved metal saturates the porous material and makes electrical connection between the anode and cathode. A specimen to be measured is introduced into the chamber. The electrolyte promotes catalytic reduction of free oxygen molecules carried by the specimen. The magnitude of current flow through a resistive load connected between the anode and cathode connectors is directly proportional to the quantity of oxygen present in the specimen.

Abstract: A gaseous carbon dioxide detection sensor comprising a detection electrode and a reference electrode opposed on both sides of an ionic conductor, wherein a mixture comprising one mol of an alkali metal carbonate more than one mol of an alkaline earth metal carbonate is used as the detection material for the detection electrode. The detection sensor has the electromotive force characteristic relative to the gaseous carbon dioxide less undergoing the effect of moisture in the gas to be measured and has a high sensitivity.

Abstract: An electrochemical gas sensor having a solid ionic conductive electrolyte therein and adapted to sense trace levels of reactive gases in the parts per million range. The electrochemical sensing cell has a pair of catalytic electrodes attached to the opposite sides of the solid electrolyte. The sensing cell is supported and contained to permit the distribution of reactant gases over the electrode surfaces for reacting thereat and thereby providing an external electrical current flow representative of the quantity of the reactant gas undergoing sensing.

Abstract: A method apparatus for constructing an oxygen sensor in a layered construction including an anode element, a cathode element and an intermediate electrolyte-retentive insulator, wherein the layered anode element has a central flat metallic plate with two narrower outer plates bound against respective surfaces of the plate by an electrical conductor wrap, and the cathode element is uniformly compressed toward the anode along an elongate length by elongated support struts.

Abstract: A sensor element for limiting current sensors for determination of the .lambda.-value of gas mixtures is proposed, which has at least one outer pumping electrode and one inner pumping electrode, on a solid electrolyte in platelet or foil form, conducting O.sup.2- ions, of which the inner pumping electrode is arranged in a diffusion channel for the measuring gas. It consists of a porous three-dimensional precious metal electrode having a supporting structure, the thickness of which electrode corresponds to the height of the diffusion channel. Characteristic of the inner pumping electrode is a greatly improved load-bearing capacity in comparison with electrodes of sheet-like design, whereby the service life of the sensor element is increased. A further advantage of the three-dimensional design of the inner pumping electrode is that it takes on a supporting function during lamination in the production of the sensor element by ceramic foil and screen printing techniques.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: An oxygen sensor or cell for measuring the oxygen content of a specimen includes a body with a chamber that houses an electrochemically active anode and an electrochemically active cathode. A chemically inert, electrically inactive porous material is dispsoed between and in contact with the anode and cathode. An anode connector is in contact with the anode and a cathode connector is in contact with the cathode. An electrolytic solution of potassium hydroxide and a dissolved metal saturates the porous material and makes electrical connection between the anode and cathode. A specimen to be measured is introduced into the chamber. The electrolyte promotes catalytic reduction of free oxygen molecules carried by the specimen. The magnitude of current flow through a resistive load connected between the anode and cathode connectors is directly proportional to the quantity of oxygen present in the specimen.

Abstract: The gas-sensing electrodes prepared according to this invention are specifically designed for cells which operate in a current-limited mode, i.e. at current densities well below 20 mA/cm.sup.2. Such cells are particularly useful to measure or detect a gaseous component of a gaseous environment or stream, provided the gaseous component can be electrochemically oxidized or reduced. In an alkaline, metal-oxygen cell for example, an electrode of this invention can be used as an oxygen cathode. The electrode is prepared by:(a) bringing an exposed face of a self-supporting, electrically-conducting sheet of fibrous or sintered-particle material having a thickness of at least about 30 .mu.m and a flexural strength of at least 2000 kPa into contact with an electrolyte containing ions of a catalytic metal, the electrolyte also being in contact with a counterelectrode,(b) applying a pulsed-D.C.

Abstract: An electrochemical gas sensor having a high surface area gas diffusing electrode defined for diffusing gases to be sensed to reach the catalyst surfaces of the electrode to provide the cathodic reduction of oxygen in a gas mixture undergoing sensing thereat. The sensor is adapted to sense trace levels of reactive gases in parts per billion. The sensor provides for ready purging of reactive gases from the electrolyte solution for the cell. The cell is essentially insensitive to the rate of flow of gas delivered to the cathode electrode and the minor mechanical stirring of the electrolyte solutions leading to output signals of improved signal-to-noise ratios more accurately signalling the concentrations of reactive gases, such as oxygen in gas mixtures.

Abstract: A method for measuring the amount of an electroactive gas in a gaseous mixture using an electrochemical cell, the cell including a working electrode (anode), counter electrode (cathode), an electrolyte in which oxygen reduction is inhibited, means for applying a variable potential across the electrodes, and means for measuring current flow between the electrode, the method involving contacting the gaseous mixture with the anode, applying a potential across the anode and cathode and cycling the applied potential between a potential level at which the gas in the gaseous mixture adsorbs onto the anode and a potential level at which the adsorbed gas in the gaseous mixture is oxidized, and measuring the current resulting from the anodic sweep portion of the potential cycle as a measure of the amount of the adsorbed gas in the gaseous mixture.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: An electrochemical device is made of a containment vessel (30) optional ceramic material within the containment vessel and including one or more electrochemical cells (10), the cells containing a porous exposed electrode (11) in contact with a solid electrolyte, where at least one of the exposed electrode, the containment vessel, and the optional ceramic material contains a deposit selected from metal oxide and metal salt capable of forming a metal oxide upon heating, where the metal is selected from the group consisting of Ce, Sm, Mg, Be, Ca, Sr, Ti, Zr, Hf, Y, La, Pr, Nb, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U, and their mixtures.

Abstract: The present invention is for an electrochemical cell and method for quantitatively detecting noxious gas which comprises a first working electrode comprising a gas diffusion membrane having bonded thereto a catalytic portion electrochemically reactive with the noxious gas; a second working electrode having electrochemical activity with the oxidation/reduction products produced at the first working electrode; a counter electrode; a reference electrode; an electrolyte; means for containing said electrolyte and said electrodes; means for maintaining a fixed potential on said first working electrode relative to said reference electrode of from about 1.0 to 1.8 volts with respect to the potential of the reversible hydrogen couple of the electrolyte of the cell; and means for maintaining a fixed potential on said second working electrode relative to said reference electrode of from about 1.0 to 2.

Abstract: A structure and method for sensing oxides of nitrogen in a gas. The gas is first passed through an oxidation catalyst and any reducing species in the gas are oxidized. The output gas from the oxidation catalyst is received by a sensor which generates an output responsive to oxides of nitrogen because the sensor has been isolated from any reducing species in the gas.

Abstract: A gas sensor includes a multi-layered solid-state pH electrode and a reference electrode coated with a gas-sensitive layer (solid-state or gel-state) sensitive to an ion of interest, the surface of the combination being coated with a gas-permable layer. Also provided in a gas sensor having a pH electrode and a reference electrode immersed in a gas-sensitive solution within a gas-permeable layer. Preferably, a fixed distance is maintained between a sensitive portion of the pH electrode, a sensitive portion of the reference electrode and the gas-permeable layer isolated by means of a porous layer. In another emodiment, the gas sensor incorporates a common electrode and a thermister for temperature calibration.

Abstract: A method for measuring the amount of an electroactive gas in a gaseous mixture using an electrochemical cell, the cell including a working electrode (anode), counter electrode (cathode), an electrolyte in which oxygen reduction is inhibited, means for applying a variable potential across the electrodes, and means for measuring current flow between the electrode, the method involving contacting the gaseous mixture with the anode, applying a potential across the anode and cathode and cycling the applied potential between a potential level at which the gaseous mixture adsorbs onto the anode and a potential level at which the adsorbed mixture is oxidized, and measuring the current resulting from the anodic sweep portion of the potential cycle as a measure of the amount of the adsorbed gas in the gaseous mixture.

Abstract: An electrochemical gas sensor for detecting the amount of a gas or vapor in an atmosphere is described having a sensing electrode and a barrier limiting the rate of access of the gas or vapor to the sensing electrode, the barrier being made of ceramics material and having an inwardly-tapering shape.

Abstract: In a catheter or hollow needle type electrolytic measuring device having a measuring electrode and a gas reference electrode, an arrangement for stabilizing the operation of the gas reference electrode includes a lipophile membrane coating a part of the gas reference electrode which communicates with an electrolyte containing space. A source of gas, preferably in the form of another electrode which release gas at a constant rate from the electrolyte, is arranged in the space opposite the gas reference electrode.

Abstract: The present invention is for an electrochemical cell and method for quantitatively detecting noxious gas which comprises a first working electrode comprising a gas diffusion membrane having bonded thereto a catalytic portion electrochemically reactive with the noxious gas; a second working electrode having electrochemical activity with the oxidation/reduction products produced at the first working electrode; a counter electrode; a reference electrode; an electrolyte; means for containing said electrolyte and said electrodes; means for maintaining a fixed potential on said first working electrode relative to said reference electrode of from about 1.0 to 1.8 volts with respect to the potential of the reversible hydrogen couple of the electrolyte of the cell; and means for maintaining a fixed potential on said second working electrode relative to said reference electrode of from about 1.0 to 2.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: In sensing diluent gases which contribute to malodors in the human breath, a detection cell is housed within the hand-held cartridge made up of inner and outer casings movable between and open and closed position. The detection cell has an electrolyte interposed between inner and outer electrodes within the inner casing and when the cartridge is advanced to its open position a sample gas stream created by blowing into the interior of the cartridge is passed into contact with the inner electrode while a reference gas stream, such as, air contacts the outer electrode whereby an electric potential is developed in response to the presence of the diluent gases indicating the presence of malodors in the human breath.

Abstract: The present invention is for an electrochemical cell and method for quantitatively detecting noxious gas which comprises a first working electrode comprising a gas diffusion membrane having bonded thereto a catalytic portion electrochemically reactive with the noxious gas; a second working electrode having electrochemical activity with the oxidation/reduction products produced at the first working electrode; a counter electrode; a reference electrode; an electrolyte; means for containing said electrolyte and said electrodes; means for maintaining a fixed potential on said first working electrode relative to said reference electrode of from about 1.0 to 1.8 volts with respect to the potential of the reversible hydrogen couple of the electrolyte of the cell; and means for maintaining a fixed potential on said second working electrode relative to said reference electrode of from about 1.0 to 2.

Abstract: Formaldehyde is determined by electrochemical oxidation of formaldehyde at an iridium electrode while maintaining the electrode at a fixed potential and measuring the current flowing through the electrode.

Abstract: An electrochemical cell for use in the detection and measurement of water soluble gases includes a vessel having a first chamber adapted to receive and contain said gas and having located therein a working electrode and a second chamber adapted to contain an electrolyte and having located therein a reference electrode arranged to be in contact with said electrolyte. A counter electrode is located in either the first or second chamber. The working electrode consists of an absorbent material communicating between said first and second chambers, which is adapted to be in contact with said electrolyte and has an electro-active substrate deposited on at least a portion of the surface of that part of the material located in the first chamber.

Abstract: An electrochemical method and apparatus for detecting polar toxic species is disclosed which uses a conductive polymer coated sensing electrode. The conductive polymers may be polyquinoline or substituted polyquinolines.

Abstract: An electrochemical measuring cell is disclosed wherein the diffusion membrane which separates the electrolyte from the ambient is made of an intrinsically-conductive and electrochemically active plastic. This way the diffusion membrane itself defines the measuring electrode of the measuring cell. This is a substantial advantage over known electrochemical measuring cells wherein the measuring electrode is defined by an electrically conductive layer applied to the surface of the diffusion membrane facing toward the electrolyte. By making the diffusion membrane from an electrochemically active plastic, a removal of the electrically-conductive layer from the diffusion membrane is prevented.

Abstract: A bias circuit (13) for an electrochemical fuel cell (15) serving for example as a carbon monoxide or hydrogen sulfide detector, including an operational amplifier tied to the anode and reference terminals (21,23) of the fuel cell (15), and a zener diode (50) arrangement for maintaining a predetermined voltage drop between the output and negative inputs of the operational amplifier (33).