Abstract: An elcctrobiochemical system for the determination of the presence and optionally concentration of an analyte in a liquid medium, the system comprising an electrode having immobilized thereon a member of a recognition pair, the other member of said pair being said analyte, the presence of said analyte in the medium resulting in formation of a pair complex, being a complex between said immobilized member and said analyte; the system further comprising redox molecules capable of changing their redox state by accepting electrons from or donating electrons to the electrode; the formation of the pair complex on the electrode bringing a change in the electrical response of the system, whereby the presence and optionally the concentration of said analyte in the medium can be determined.

Abstract: An apparatus for cleaning a gas sensor and a method therefor are disclosed. A high voltage is supplied to a heat generating body of the gas sensor for a certain period of time to generate a large amount of heat within a short period of time so as to remove the moisture or miscellaneous gases absorbed into on the surface of the gas sensor, thereby stabilizing the characteristics of the gas sensor. The apparatus includes: a power supply section for receiving an ac voltage from a commercial ac power source to convert it into a rated voltage and an excessive voltage exceeding the rated voltage; and a switching section for supplying the rated voltage to the gas sensor after supplying the excessive voltage of the power supply section to a heat generating body of a gas sensor for a certain period of time.

Abstract: A method of controlling the oxidation of sulfites in a flue gas desulfurization process involves treating the exhaust gas with an absorbing fluid containing a calcium compound and controlling the oxidation of sulfites by regulating oxygen flow into the absorbing fluid. Oxygen flow is controlled by continuously monitoring the oxidation-reduction potential (ORP) of the absorbing fluid relative to the same fluid in a completely oxidized state using a detector with a plurality of fluid tanks, one of which functions as a reference tank at any particular time. The fully oxidized reference tank is periodically switched, reducing adherence of oxidizing substances to the ORP electrodes, resulting in more accurate measurements and reduced chemical oxygen demand of the waste water.

Abstract: A CO.sub.2 sensor includes a body of solid electrolyte ceramic with alkali ion conductivity, and two electrodes of conductor material being inert with respect to the solid electrolyte ceramic. At least one of the electrodes is at least partially permeable, and the solid electrolyte ceramic is galvanically prepolarized. A measurement circuit configuration includes the CO.sub.2 sensor and a voltage measuring device coupled to the electrodes of the solid electrolyte ceramic body.

Abstract: Fluid transmission pipelines and similar structures which are cathodically protected from electrolytic corrosion and are disposed in urban areas under pavements and other structures which prevent access to the soil for verifying pipe-to-soil potentials are subjected to pipe-to-soil potential measurements using a reference electrode disposed in a container which has a permeable bottom and which is capable of saturating a pavement layer with a brine electrolyte to provide electrical conductivity between the reference electrode and the soil. Validation of electrical conductivity is made by a second reference electrode of a dissimilar metal which is also disposed in a container having a permeable bottom and an electrolyte which permeates the pavement layer and establishes electrical conductivity between the soil and the second reference electrode. Potential measurements between the first and second electrodes validate ion transport between the soil and the first reference electrode.

Abstract: A chemical sensor includes a thin film transistor with a gate positioned on one side. An insulating layer is positioned on the opposite side and an indicator film is positioned on the insulating layer in generally opposed relationship to the gate. Induced charge in the indicator film caused by a biological or chemical species changes the channel current in the transistor. A potential on the gate is then used to null out the resulting change in channel current. The potential used to null out the current change is an extremely sensitive measure of the induced charge.

Abstract: Apparatus and method are provided for determining the concentration of an analyte in a fluid test sample by applying the fluid test sample to the surface of a working electrode which is electrochemically connected to a reference electrode which surface bears a composition comprising an enzyme specific for the analyte. A mediator is reduced in response to a reaction between the analyte and the enzyme. An oxidizing potential is applied between the electrodes to return at least a portion of the mediator back to its oxidized form before determining the concentration of the analyte to thereby increase the accuracy of the analyte determination. Following this initially applied potential, the circuit is switched to an open circuit or to a potential that substantially reduces the current to minimize the rate of electrochemical potential at the working electrode. A second potential is applied between the electrodes and the current generated in the fluid test sample is measured to determine analyte concentration.

Abstract: A Clark-type gas detection apparatus includes a sensor electrode and a reference electrode exposed to an aqueous electrolyte solution which is isolated from a liquid medium surrounding the apparatus by a semi-permeable membrane. A preferred reference electrode for use in Clark-type apparatus comprises silver/silver chloride. Through the addition of an effective amount of a sulphate-based co-electrolyte to an electrolyte solution having a relatively low chloride ion content, it is possible to obtain an electrolyte solution having an ionic conductivity comparable to that of chloride-based electrolyte solutions currently used in Clark-type sensors while retaining sufficient chloride ion to drive the oxidation reaction near the reference electrode. The relatively low chloride ion content of the electrolyte solution of the present invention tends to suppress the dissolution of silver chloride from the reference electrode, and, consequently, the deposition of silver on the indicating electrode.

Abstract: High power density electrochemical capacitors may be pretreated by immersing the electrodes therefore in an alkaline solution. Thereafter the immersed electrode are subjected to high power pulses for brief periods of time. The pretreatment process forms an activated oxide layer on the electrode surface. The resulting device is capable of delivering high current pulses with enhanced discharge voltage.

Abstract: To avoid a reduction of the conductivity in iontophoresis due to the electrical decomposition and the changes in chemical properties of the electrodes themselves, covering by an electrical insulator, and to prevent a drop in the transport rate due to ions freed from the electrode. Provision is made of an electrode structure provided integrally with a reversible electrode and an auxiliary electrode for regeneration of the same and a regeneration current conducting means for conducting a current for regeneration of the reversible electrode when the therapeutic current is off, or the invention is comprised of a reversible electrode and an ion exchange membrane difficult for ions freed from that electrode to penetrate.

Abstract: Apparatus and method are provided for determining the concentration of an analyte in a fluid test sample by applying the fluid test sample to the surface of a working electrode which is electrochemically connected to a reference electrode which surface bears a composition comprising an enzyme specific for the analyte. A mediator is reduced in response to a reaction between the analyte and the enzyme. An oxidizing potential is applied between the electrodes to return at least a portion of the mediator back to its oxidized form before determining the concentration of the analyte to thereby increase the accuracy of the analyte determination. Following this initially applied potential, the circuit is switched to an open circuit or to a potential that substantially reduces the current to minimize the rate of electrochemical potential at the working electrode. A second potential is applied between the electrodes and the current generated in the fluid test sample is measured to determine analyte concentration.

Abstract: A solid shale, multi-use electrochemical sensor having an electrically nonconductive substrate, a working electrode, and a semi-permeable membrane covering the working electrode. The working electrode includes an electrically conductive material adhered to a portion of the substrate. A first portion of the conductive material is covered with an electrically insulating dielectric coating, and a second portion of the conductive material is covered with an active layer. The active layer includes a catalytically active quantity of an enzyme carried by platinized carbon powder particles, which are distributed throughout the active layer. A sensor package for incorporating a sensor is provided.

Abstract: Fluid transmission pipelines and similar structures which are cathodically protected from electrolytic corrosion and are disposed in urban areas under pavements and other structures which prevent access to the soil for verifying pipe-to-soil potentials are subjected to pipe-to-soil potential measurements using a reference electrode disposed in a container which has a permeable bottom and which is capable of saturating a pavement layer with a brine electrolyte to provide electrical conductivity between the reference electrode and the soil. Validation of electrical conductivity is made by a second reference electrode of a dissimilar metal which is also disposed in a container having a permeable bottom and an electrolyte which permeates the pavement layer and establishes electrical conductivity between the soil and the second reference electrode. Potential measurements between the first and second electrodes validate ion transport between the soil and the first reference electrode.

Abstract: A water purity testing system includes a sensor housing having an internal chamber within which pair of electrodes are supported. Fittings are provided for coupling the housing to a water supply and introducing water into the chamber. A temperature sensor is supported within the housing. A system processor and control unit is operatively coupled to the electrodes and the temperature sensor and includes a source of voltage DC current measurement which is applied to the electrodes to facilitate the measurement of water conductivity within the housing chamber, followed by a grounding period to provide as settling time to prevent the build-up of debris on the electrodes. The microprocessor also utilizes the temperature measurement during the testing cycle to derive a temperature factored measurement of total dissolved solids within the water under test. A display system is coupled to the microprocessor and is operated under microprocessor control to provide a test result display output.

Abstract: A carbon electrode is dipped in a solution containing a reactive substance, and the carbon electrode impregnated with the solution is covered with an insulating tubular member; or a solution containing a reactant is poured into an insulating tube, and a carbon electrode is inserted into the tube; whereby the reactant is made coexistent in the periphery of the carbon electrode. Alternatively, a reactive substance such as an active enzyme and graphite particles or activated carbon particles are mixed with a liquid and dispersed therein to prepare a thoroughly wetted paste. The paste is introduced by means of an extruding mechanism such as a syringe into an insulating tubular member in which a bundle of many thin carbon rods as a lead is inserted. Thus, a carbon sensor electrode is produced. Alternatively, a first carbon electrode that has been dipped in an active enzyme or an enzyme-like reactive substance solution is disposed in a wet condition in a cylindrical ion permeable membrane.

Abstract: In a sensor such as a pH sensor, a bundle of relatively long, thin and soft cleaning filaments is anchored next to the pH electrode. A bluff body, which may be the reference electrode is positioned upstream of the bundle so as to create liquid vortices which move the free ends of the fibres in an effective cleaning action over the sensing surface of the pH electrode.

Abstract: A sensing element, for use in determining the presence and/or concentration of a species in a solution, comprises a flat insulating substrate (10) having at least one thin metallic electrode (16) deposited on it and overlaid with an insulating layer (20). The electrode (16) and insulating layer (20) bridge a weakening groove (12) formed in the substrate. Immediately before use, the element is broken along the groove to expose a cross-sectional surface (24) of the element, and thus a cross-sectional working surface (26) of the electrode. The thickness (T) of the element is comparable to or less than the concentration boundary layer thickness of the solution. This exposed working surface is the only part of the electrode in contact with the solution. In use, the element can be vibrated so as to improve its sensitivity.

Abstract: A method of measuring the silver ion activity of a mixed halide solution or dispersion comprises measuring the potential difference between a silver halide coated silver electrode and a reference electrode immersed in the solution or dispersion. Prior to measuring the potential difference an electrical pulse is applied to the silver electrode which in a first phase electrochemically strips the electrode surface and in a second phase electrochemically coats the electrode with a silver halide having the halide ion ratio of the solution or dispersion.

Abstract: Device for prolonging the effective usage time (service life), arrangement and process for minimizing temperature effects in any ion-selective polymer membrane electrode measuring chain (ISPE measuring chain), wherein one solution or both solutions directly adjoining the polymer membrane (outer measuring solution and inner potential drain solution) are saturated or supersaturated with the compounds which normally tend to bleed out; and wherein the isotherm intersection of an ion-selective measuring chain with redox drain elements is optimally located in the middle of the measuring range such that this middle is located at ca. 0 mV.The device may be used for monitoring of groundwater with opposite changes in the concentrations of nitrate and ammonium, evaluated in a special device, with electronic data processing and intermediate data storage (in RAM pack) at the site of the measurement and data polling as needed to a central unit by telemetry.

Abstract: A method of making and an amperometric electrode are provided. An electrode carbon ink is applied to a polymer substrate to form a working electrode. The substrate carrying the working electrode is placed in a gas plasma cleaner, such as an oxygen or nitrogen plasma, to clean the working electrode. A high radio frequency signal excites the gas plasma for a short exposure time in a range between 10 seconds and 30 seconds. Then a reagent layer is deposited to the plasma treated working electrode.

Abstract: A method of improving the utility of electrochemical glucose sensors by decreasing either or both their settling time and their sensitivity to interfering compounds. In particular, the settling time of an electrochemical glucose sensor is improved by pretreating the operating electrode with a negative electric current at a constant current density. The sensor's sensitivity to intefering compounds is reduced by operating the sensor at a reduced voltage while the glucose concentration measurement is being made.

Abstract: A non-enzymatic implantable glucose blood detector. The detector makes use of a non-reactive tin oxide semiconductor measurement electrode which is suitably energized by an electrical power source. Variations in current density at the measurement electrode are related to variations in glucose content of blood. The device also uses variable voltage to allow the electrode to be self-cleaning.

Abstract: Method and apparatus for electrochemical monitoring of oxidizing agents, such as nitrite, or reducing agents in a water system and for controlling concentration levels for protecting surfaces exposed to the water. The apparatus includes a probe for selective exposure to fresh water samples of the system. The probe is connected to an analyzer that operates the probe and measures agent concentration by a chronoamperometry technique. A controller selectively feeds an agent to the water system in accordance with a set point to maintain a desired concentration level.

Abstract: After a reverse bias is applied between a working electrode and a counter electrode or a reference electrode, a forward bias higher than a forward measurement bias is applied between the working electrode and the counter electrode or the reference electrode, before the forward measurement bias is applied. This reduces the time period before which an actual measuring operation is possible. When the bias is applied between the working electrode and the counter electrode or reference electrode, the bias is gradually increased in absolute value according to a predetermined time constant. This reduces damage to the membrane or membranes fixed on a surface of the electrode unit.

Abstract: A method is disclosed for greatly reducing pacing polarization of a porous platinum bioelectrical stimulation electrode substrate by applying an oscillating current to the electrode substrate while it is immersed in an electrolyte such as a sodium sulfate solution to electrochemically cause the formation of a thick, highly porous platinum hydrous oxide surface layer on the substrate. The surface layer is then slowly reduced to platinum, while maintaining an increased surface area structure therein, using a similar electrochemical process employing much lower levels of current. This method does not alter the electrode characteristics other than to increase the microsurface area. The reduced polarization follows from the known inverse relationship between microsurface area and polarization. An electrode made by the foregoing method is also disclosed.

Abstract: A method of preconditioning an electrode for use in a plating bath monitoring process. The method involves applying at least one anodic signal to an electrode in contact with the plating bath solution in order to yield a reproducibly clean and stabilized electrode surface, and then applying a plating signal to deposit a layer of metal on the anodically treated electrode. The resultant preconditioned electrode improves the accuracy and precision of subsequent voltammetric monitoring measurements for a variety of different plating baths. The method is easily integrated with and thereby enhances the capabilities of known voltammetric plating bath monitoring processes.

Abstract: A method of monitoring a plating bath which combines ac and dc voltammetry to accurately measure major and trace constituent concentrations. The method involves applying both ac and dc voltammetric signals to a pretreated electrode in contact with the plating bath solution, measuring the ac and dc response current spectra, and comparing the resultant spectra to determine which provides maximum spectral detail for monitoring particular constituents with minimum interference from other constituents. Then, the ac and dc response current spectra are each used to monitor the particular constituents for which each provides the best accuracy. The method complements and is easily integrated with known voltammetric techniques and equipment.

Abstract: A method for monitoring the status of a plating bath purification treatment cycle. The method involves applying a swept dc measurement signal to a pretreated electrode which is in contact with the plating solution, and monitoring the resultant response current signal. The electrode potential corresponding to the peak current density in the cathodic sweep of the response current signal provides an accurate indication of the status of the purification treatment cycle. The method tracks the progress of the purification process thereby ensuring the optimal termination points for the treatment process. The method can be used in conjunction with voltammetric plating bath analysis methods and equipment, as part of an overall plating bath monitoring and control system.

Abstract: A method of forming a reference electrode having a continuously stable reference voltage and particularly well-suited for use in an in-tank electrochemical sensor. The method utilizes an inert substrate and a counter electrode, both immersed in electroplating fluid. Current is passed between the inert substrate and the counter electrode to strip and subsequently replate the inert substrate, which then serves as the reference electrode. The steps of stripping and replating the reference electrode are periodically repeated to maintain the stability of the reference electrode voltage.

Abstract: A concentration measuring apparatus includes an enzyme electrode which accelerates an oxidation reaction or a reduction reaction of a test substance in a liquid and outputs an electrical signal corresponding to a quantity of the test substance therefrom due to the reaction. The enzyme electrode is supplied with a reviving voltage for removing interfering substances on the enzyme electrode not only prior to concentration measuring but also according to a predetermined time interval. The reviving voltage has a polarity which is the reverse of the voltage used for concentration measurement.

Abstract: A sensor electrode and method for detecting select characteristic in a liquid. The method utilizes filters and adsorbent materials to selectively remove contaminants in the liquid. The improvement comprises back flushing the filters and adsorbent material, once they become saturated, with specific solutions to wash away the select contaminants.

Abstract: This invention provides an electrochemical sensor capable of measuring the glucose level of body fluids, especially blood. More particularly, this invention also relates to the use of such a glucose sensor in an automated bedside blood chemistry system which facilitates the operation of the sensor.

Abstract: An enzymatic electrode, having a homogeneous composition throughout, consists essentially of a uniform intimate admixture of a conducting powder with at least one immobilized enzyme, or with an immobilized enzyme and a mediator agent or a co-enzyme, in a matrix. The electrode is one which has a surface available for direct contact with a substrate without a permeable or semi-permeable intermediate membrane or membranes. The enzymatic electrode is prepared, e.g., by intimately admixing (a) a homogeneous paste or matrix (resulting from an intimate admixture of a conducting powder with a binder), (b) at least one enzyme and (c) an enzyme crosslinking solution, and then incorporating therein a mediator agent and/or a co-enzyme.

Abstract: A method is provided for measuring the concentration of a constituent of a fluid sample, e.g. glucose in a glucose-containing blood sample, by means of an electrode device. Also provided are an electrode device comprising the electrodes used in the method, a sensor electrode for use in the method, and an apparatus for use in the measurement of the concentration of the constituent in the sample.

Abstract: Apparatus for measuring fluid flow through a conduit including a measuring electrode and a ground electrode disposed in the conduit and connected to form an electrolytic cell, so that a voltage can be applied between the electrodes in order to cleanse deposits from the measuring electrode, and gases generated during the cleansing step can then be dissipated. Methods for measuring the fluid flow in such a manner are also described herein.

Abstract: Improved circuits for measuring the conductivity of a solution confined between two electrodes in a cell compensate for series capacitance and parallel capacitance between the electrodes. A bipolar square-wave signal is applied to the cell. In one embodiment, the current through the cell is measured by an op-amp in current-to-voltage converter configuration. A feedback resistance employed with the op-amp in a feedback loop is controlled to a low value to ensure that the parallel capacitance is fully charged during an initial portion of each half-cycle of the drive signal. The feedback resistance is then selected so that the gain of the feedback loop is responsive to the range of the resistivity of the solution, and the measurement is made. The period of the bipolar signal is selected responsive to the selected loop gain, to ensure that a filter capacitor across the op-amp is fully charged, and to limit distortion caused by the series capacitance.

Abstract: An easily installed, automatically operated sanitizing direct current, electrolytic cell canister assembly and a method of efficiently providing brominated water for swimming pools and the like, the method including furnishing d.c. power at a constant amperage to the bipolar electrode graphite plate electrolytic cell canister, controlling the flow of electrolyte through the canister, turning the d.c. current on and off to provide d.c. on/off switching, turning the d.c. power off, adjusting the time of the on/off switching so that the current is off for a predetermined selected time in a cycle of about 1 to 60 seconds, and, just prior to reversing the polarity of the electrodes, turning the power off for about five seconds, with separate polarity changing switching to help efficiently clean the graphite plates and keep the bromine atoms from going back to their ionized state and reduce any power surge due to the reversal of the polarity.

Abstract: The invention provides an apparatus and method for determining levelling power of an electrolyte. An anode and cathode are immersed in the electrolyte. The cathode has a plating surface for electrodeposition of a metal from the electrolyte. The plating surface has a peak region and a base region separated and electrically isolated by an insulator. The peak region has a greater tendency to electrodeposit the metal per unit surface area than the base region. The anode and cathode are placed in a test cell or suspended in a commercial electrodeposition cell. A means for applying current between said anode and said cathode is used for causing the metal from the electrolyte to electrodeposit on the plating surface of the cathode. The current from plating on the peak region and the base region are measured separately to determine levelling power of an electrolyte.

Abstract: The invention is directed to an electrochemical measuring cell for measuring ammonia or hydrazine and includes at least a measuring electrode and a counter electrode in an electrolyte. The measuring cell provides a signal increase having a shorter response time and an improved signal stability. For this purpose, the electrolyte is an aqueous solution of a hygroscopic salt of an alkali metal or earth alkali metal such as calcium nitrate or lithium nitrate or a mixture of both salts.

Abstract: An apparatus for electrochemically determining the partial oxygen pressure pO.sub.2 in a liquid measuring medium includes a measuring sensor having a working electrode and a counter-electrode. The electrodes are manufactured in thin-film technology and are arranged on a substrate in a measuring channel, to which the measuring medium and a rinse medium can be supplied in alternation. The measuring channel connects a device which controls the flow rate of the measuring medium to a lumen of a double lumen catheter. The rinse medium is suppliable to a second lumen of the double lumen catheter with reversible flow direction. Both lumens have a common orifice which can be introduced into the measuring medium. So-called poisoning of the electrodes in this arrangement is suppressed because the electrodes are flooded in alternation by the measuring medium in a measuring phase and by the rinse medium in a regeneration phase.

Abstract: In a streaming current detector, a standard calibration solution is used to calibrate the streaming current signal representing the charged condition in a sample fluid containing particles. The standard calibration solution is electrokinetically stable over a wide range of pH and concentration. Calibration allows direct comparison of readings from different streaming current detectors.

Abstract: The invention is directed to an electrochemical measuring cell for determining ammonia or hydrazine in a gaseous or liquid measuring sample. The measuring cell has at least one measuring electrode and at least one counter electrode which are disposed in an electrolyte chamber filled with a soluble electrolyte containing a cobalt salt dissolved therein. The electrolyte chamber is closed off in the direction facing toward the measuring sample by a permeable membrane. The measuring cell provides a selective ammonia measurement having the following advantages: a short response time, a linear response and a low tendency to drift. The electrodes of the measuring cell are so configured that the oxidation of the ammonia as a measurement reaction has no influence on the sensitivity of the measuring cell. For this purpose, at least the measuring electrode is provided with a coating containing cobalt oxide which is in direct contact with the electrolyte.

Abstract: A cyclic voltammetric method for measuring concentrations of subcomponents of additive mixtures, comprising the steps of: (a) preparing a basis solution which contains all of the components of an unknown solution to be measured, except a component of interest; (b) preparing a calibration solution which contains the component of interest in a known concentration near that which would be expected in the unknown solution; (c) adding measured amounts of the calibration solution to a first defined volume of the basis solution and plotting a first cathodic charge against the added volume of the calibration standard; (d) adding measured amounts of the unknown solution to a second volume of the basis solution and plotting a second cathodic charge against the added volume of the unknown solution; and (e) comparing the slopes of the first and second curves to determine the concentration of the component of interest in the unknown solution.

Abstract: A device for in situ cleaning a fouled membrane of a sensor disposed in an aqueous process solution includes a first electrolysis electrode disposed in the process solution immediately adjacent the membrane, a second electrolysis electrode disposed in the process solution and spaced apart from the first electrolysis electrode, and a controllable power source for passing a current between said first and second electrodes. The current produces a heavy concentration of ions at a surface of the fouled membrane. The polarity of the current is selectable to produce negative or positive ions for reacting to decompose deposited salts, or to scrub contaminates from the membrane surface.

Abstract: One of the fundamental limitations of voltammetric detectors in flow analysis is the problem of passivation or contamination of the working electrode. The present invention proposes a voltammetric detector based on the wall-jet principle which incorporates the concept of a replaceable working electrode. The voltammetric detector represents a significant improvement over existing detectors which are fully enclosed or sealed devices precluding easy replacement of the working electrode.The design of the present invention provides a detector where the top is fully open and where the solution volume is maintained by the outlet positioning. The other feature of the proposed detector is an optimised geometry that provides well defined wall-jet flow characteristics which is not provided in existing detectors.

Abstract: A method of determining the concentration of a preselected analyte species present in a sample fluid is disclosed, which method comprises: (a) providing an external computational means, a reference electrode and at least one substantially dry-stored sensor capable of exhibiting a response to changes in the concentration of a preselected analyte species before the sensor attains full equilibrated wet-up; (b) establishing electrical contact between the sensor, reference electrode and external computational means; (c) contacting the sensor and reference electrode with a calibrant fluid; (d) performing a first signal measurement in a first time window in the presence of the calibrant fluid; (e) displacing the calibrant fluid after performing the first signal measurement; (f) contacting the sensor and reference electrode with a sample fluid; (g) performing a second signal measurement in a second time window in the presence of the sample fluid; and (h) relating the first and second signal measurements to determine

Abstract: An improved electrode cleaning system for an electrochemical sensor is disclosed. The improved electrode cleaning system includes a flexible wiper blade which is biased against a flat wiping surface formed by electrodes having a flat detection surface and a collar placed around the electrodes to prevent particulates from depositing between the electrodes. The collar is secured to the sensor by a recessed screw which also serves as a common electrical ground. The flexible blade preferably has two wiping portions for alternately wiping the electrodes and the common ground screw.

Abstract: A testing module is provided having units which can be arranged seriatim to provide narrow through passageways linked to each other for quantitative determination of analytes passing through the units as by electrical testing with electrodes. Auxiliary passageways are preferably used in one unit to allow flushing of a first sample chamber without contamination from a second sample chamber. An electrode holder carries a membrane backed by a gel to aid in electrically linking the membrane to an electrode and to support the membrane in a substantially planar condition in use.

Abstract: The invention is directed to a dosimeter for detecting gaseous substances or substances dissolved in liquids. The dosimeter includes a detection chamber which is partitioned off with respect to the ambient by a membrane which is permeable to the substance to be detected. The detection chamber is filled with an electrolyte which is subjected to changes in its characteristic under the action of the substance to be detected and these changes can be evaluated as electrical measured values via appropriate electrodes. The electrolyte contains a reagent which goes into an irreversible reaction with the substance to be detected and the dosimeter is improved so that after the evaluation it can be used again for measuring tasks or for collecting the substance to be detected. Furthermore, a calibration or a function test can be carried out on each dosimeter without its measurement readiness being limited thereby.

Abstract: In a method for the electrical measurement of the concentration of acids a measurement electrode (11) consisting at least predominantly of crystalline graphite is arranged in an acid (12) having anions which form graphite intercalation compounds with graphite. The measurement electrode (11) is then intercalated by generating in the measurement electrode (11), at a variable positive potential, a current of such a size that the anions of the acids (12) can from graphite intercalation compounds with the graphite. The current is maintained until the intercalation compounds have formed at the surface. The potential at the measurement electrode (11) is then measured and used as a measure for the acid concentration. The measurement electrode (11) is subsequently deintercalated again.