Abstract: An electrolysis plate is described which consists of an outer non-conductive frame, particularly a frame having a fiber-reinforced cresol resin, an electrically conductive, bipolar graphite plate which is mounted therein and is preferably slotted on both sides, and, in the region of the electrolyte feed, has plastic skirts for the forced direction of the electrolyte solutions.

Abstract: Dioxins are eliminated from soot by conversion into oil and water. A gas stream of smoke and dioxin-entraining ash is passed through a curtain of water in a separator to separate the dioxin-entraining ash from the gas stream. The ash-water mixture is separated by a centrifuge, the separated ash is mixed with water and the mixture is again separated by a centrifuge into ash and an emulsion-like oil-water mixture in which dioxins are dissolved. This separated ash is also washed with water and the various wash waters and the dioxin-containing oil-water mixture are admixed and electrolyzed in a primary electrolyzer equipped with a carbon anode and a stainless steel cathode to decompose the dioxin components. The remaining aqueous liquid is electrolyzed in a secondary electrolyzer with an aluminum anode and a stainless steel cathode to generate hydrogen by electrolysis of water and metal hydroxides by electrolysis of aluminum.

Abstract: An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises molten electrolyte having the following ingredients: AlF3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound is, a fluoride; oxide, or carbonate. The metal is nickel, iron, copper, cobalt, or molybdenum. The bath is employed in a combination including a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the instant bath during electrolytic reduction of alumina to aluminum improves the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

Abstract: An electrochemical treating apparatus comprising an electrolytic cell comprising an anode and a cathode spaced apart from the anode, the anode including an electrode material made of diamond and the cathode including an electrode material made of diamond. Also disclosed is an electrochemical treating method for electrochemically decomposing a substance contained in a gas or solution, which comprises introducing a gas or solution containing a substance to be treated into the electrolytic cell, passing an electric current through the electrolytic cell, and recovering a treated gas or solution. In a preferred embodiment, the electrolytic cell comprises an anode including an electrode material made of diamond, a cathode including an electrode material made of diamond and an ion exchange resin or an ion exchange membrane as an electrolyte disposed between the anode and the cathode.

Abstract: Carbon-containing components of cells for the production of aluminium by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: Gas Diffusion Electrodes (GDEs) play a pivotal role in clean energy production as well as in electrochemical processes and sensors. These gas-consuming electrodes are typically designed for liquid electrolyte systems, and are commercially manufactured by hand or in a batch process. However, CDEs using the new electrolytes demand improved electrode structures. This invention pertains to GDEs and gas diffusion media with new structures for systems using membrane electrode assemblies (MEAs), and automated methods of manufacture that lend themselves to continuous mass production. Unexpected improvements in gas and vapor transport through the electrode are realized by incorporating a new dispersion process in the construction, reformulating the applied mix with solution additives, and creating a novel coating structure on a conductive web. Furthermore, combining these changes with a judicious choice in coating methodology allows one to produce these materials in a continuous, automated fashion.

Abstract: A cell for the production of aluminium by the electrolysis of an aluminium compound dissolved in a molten electrolyte, in which an outer mechanical structure forming an outer shell (21) houses therein one or more inner electrically-conductive cathode holder shells or plates (31) which contain a cathode mass (32) and is/are connected electrically to the busbar. The cathode mass (32) has an aluminium-wettable top surface (37), preferably at a slope forming a drained cathode. The inner cathode holder shell or shells (31) is/are separated from the outer shell (21) by an electric and thermic insulation (40), the cathode holder shell(s) (31) also serving to distribute current uniformly to the cathode mass (32). The or each cathode (30) formed by the cathode holder shell (31) and cathode mass (32) is removable from the cell as a unit.

Abstract: Magnesium metal is produced by electrolysis of magnesium chloride employing a high surface area anode, for example, a porous anode to which hydrogen gas is fed. Hydrogen chloride is formed from the chloride ions at the anode, rather than chlorine gas; the process also has the advantage of operating at a lower voltage with a lower energy requirement than the conventional process in which chlorine gas is generated at the anode.

Abstract: The present invention refers to an anode composition comprising as binding agent the sugar cane molasses, mascavo sugar, brown sugar or demerara, VHP, crystal, refined or hard sugar, instead of the conventional electrolytic pitch. The composition may optionally include additives based on lithium, fluorine, aluminum, boron and sulfur, and is used in a process for the manufacture of anodes for the primary aluminum industry. The invention also refers to a process for the manufacture of said anode and the application thereof to the primary aluminum industry.

Abstract: An array of selectively addressible microelectrodes for combinatorial synthesis of complex polymers or alloys.

Abstract: An electrolytic method is disclosed by which occlusion of hydrogen or sticking of atoms or molecules in plating and so forth is not disturbed by electronic magnetic force produced by main electric current and ion current flowing from the positive electrode to the negative electrode through electrolyte. An electric circuit separate from a positive electrode and a negative electrode is provided between the positive electrode and the negative electrode, and electric current of a direction opposite to that of main electric current and ion current flowing in the electrolyte from the positive electrode to the negative electrode is supplied to the electric circuit to produce an opposite magnetic field which cancels a magnetic field produced by the main electric current and the ion current flowing in the electrolyte.

Abstract: The present invention provides a graphitized cathode block for aluminum smelting obtained by forming a raw material containing at least one calcined coke selected from the group consisting of calcined petroleum coke and calcined pitch coke, and a binder; baking the formed material to give a non-graphitized block; and graphitizing the non-graphitized block by resistive heating; wherein both end portions of the block have a higher electrical resistivity than the center portion thereof. By employing the cathode block of the present invention, during electrolytically smelting aluminum, current may be uniformly flowed as the concentration of current at both end portions of the cathode block is lightened, and it becomes possible to maximize the advantages of graphitized cathode blocks.

Abstract: An electrochemical cell system is disclosed, wherein a MEA is provided within a vessel. The MEA includes a first electrode, a second electrode, and a membrane disposed between and in intimate contact with the first electrode and the second electrode. The vessel is disposed around the MEA, and defines a first storage area in fluid communication with the first electrode. The MEA defines a second storage region in fluid communication the second electrode.

Abstract: For eliminating dioxins from soot containing dioxins adhering to incineration ash by decomposing them, in an easy and simple manner and at low cost, into a harmless and useful oil and water and recovering the oil and water, a mixed gas 3 composed of smoke and dioxin-entraining ash is passed through a particulate matter separator 6, where the mixed gas passes through a curtain of water 5 to cause the dioxin-entraining ash to be taken up in water. The ash-water mixture is separated into ash and water on a centrifuge 12. The ash is washed with washing water 22 to elute the oleaginous dioxins entrained by the ash to give an emulsion-like oil-water mixture and the resulting mixture is separated, by means of a centrifuge 23, into ash and the emulsion-like oil-water mixture in which dioxins are dissolved. This ash is washed first with acidified water 26, then with alkaline washing water 28 and further with neutral water 29, followed by separation into moist ash and aqueous washings.

Abstract: The invention concerns a diaphragm chlor-alkali electrolysis cell comprising a cover, a conductive base for supporting the anodes and a cathode in the form of a box provided with internal wall, external wall and tubular fingers made of a mesh or perforated sheet covered with a porous diaphragm. One or more copper sheets for electric current distribution are fixed to the cathode external walls. The connection between the copper sheets and the cathode external walls is made by means of bolts with the interposition of a conductive and deformable element provided with residual elasticity under compression. The weldings for the assembling of the cathode walls are free from internal stresses.

Abstract: An ozone generator which operates at constant pressures to produce a continuous flow of ozone in an oxygen stream having from 10% to 18% by weight of ozone. The ozone generator includes one or more electrolytic cells comprising an anode/anode flowfield, a cathode/cathode flowfield, and a proton exchange medium for maintaining the separation of ozone and oxygen from hydrogen. The ozone generator also has an anode reservoir which vents oxygen and ozone and a cathode reservoir which vents hydrogen. The anode reservoir can be filled from the cathode reservoir while continuing to produce ozone. The ozone generator is readily configured for self-control using a system controller programmed to operate the anode reservoir at a constant pressure.

Abstract: An electrode comprises a non-conductive substrate and a conductive layer comprising, in a bonded matrix, graphite particles coated with a noble metal, and carbon particles, wherein the graphite particles are up to 20 &mgr;m is size and have a surface area of 1-50 m2/g. This electrode is capable of measuring low levels of analyte, e.g. glucose in sweat when convined with a layer containing glucose oxidase.

Abstract: Carbon-base bipolar electrode for electrochemical redox reactions in an acid electrolyte in the form of a fluid impervious and electrically conductive septum, at least a face of which consists, at least partially, of a fluid previous woven or unwoven electrodically active fabric of carbon fibers or of yarns of carbon fibers, has an electrically conductive fluid impervious septum consisting of a composite of a matrix fabric in the form of a tightly knit or woven fabric of carbon fibers or of yarns of carbon fibers the pores of which are hydraulically sealed by an electrically conductive carbon containing material at least partly filling the pores of said matrix fabric.

Abstract: Gas-diffusion electrodes containing modified carbon products are described wherein the modified carbon product is a carbon product having attached at least one organic group. The modified carbon product can be used for at least one component of the electrodes such as the active layer and/or the blocking layer. Methods to extend the service life of electrodes as well as methods to reduce the amount of fluorine containing compounds are also described.

Abstract: An electrolytic cell for the recovery of silver from a photographic fixer solution has a cylindrical cathode secured to and depending downwardly from a screw-on lid of the cell into the solution. The cathode is formed from a sheet of graphite foil laminated to a polyester base, and is clamped at its upper periphery around a boss of the lid. A metal connection ring is embedded around the outer periphery of the base and is contacted by the cathode. This arrangement is particularly suitable for allowing a thin, flexible disposable cathode to be conveniently removed from the cell by means of the lid, without the user being exposed to contact with the silver or with the solution.

Abstract: The present invention relates to a process for improving the adhesion of metal particles to a carbon substrate, characterized in that, before the said metal particles are deposited on the carbon substrate, the said substrate is treated in an alkaline medium at a temperature of between 50° C. and 100° C. in a stream of a gas containing oxygen.

Abstract: The present invention relates to the use of petroleum coke for the manufacture of carbonaceous anodes for the aluminum smelting industry. The inclusion of Group 4 and/or Group 13 metal compounds as additives to the petroleum coker feedstock diminish the oxidizing tendencies of the metal impurities inherent in the petroleum coke.

Abstract: The present invention refers to an anode composition comprising as binding agent the sugar cane molasses instead of the conventional electrolytic pitch. The composition may optionally include additives based on lithium, fluorine, aluminum, boron and sulfur, and is used in a process for the manufacture of anodes for the primary aluminum industry. The invention also refers to a process for the manufacture of said anode and the application thereof to the primary aluminum industry.

Abstract: A method for pickling products in a metal alloy containing iron, and products in titanium and alloys thereof, in the absence of nitric acid as an oxidizing agent, and for the recovery of the exhausted solutions, characterized in that the recovery of the exhausted solutions deriving from pickling comprises the following steps: sending of the pickling solution, both as catholyte and as anolyte, in an electro-chemical cell optionally of the membrane type to separate the Fe2+ (or Ti2+) ions to be disposed of, from the Fe3+ (or of the Ti3+ and Ti4+) ions to be recovered, obtained by reduction at the cathode of the Fe3+ ions which are in the catholyte to Fe2+ (or of the Ti3+ and Ti4+ ions to Ti2+) and of oxidation at the anode Fe2+ (or Ti2+) ions which are in the anolyte to Fe3+ (to Ti3+ and Ti4+); treating the catholytic solution coming out of the cell and enriched in Fe2+ (or Ti2+) ions as to allow the separation in two phases, a

Abstract: An electrolysis cell for carrying out chemical reactions include an electrolyte chamber (2) with a fixed-bed electrode (2F), a gas chamber (1) filled with filling bodies (1F), a gas diffusion electrode with an ion-exchanging separator (3) applied on the electrolyte-chamber side. The ion-exchanging separator is applied onto the gas diffusion electrode by a method comprising a single or multiple application of a solution of an ion-exchanging material in a solvent onto the electrocatalytically active layer of the gas diffusion electrode and at least partial evaporation of the solvent after each coating. The electrolysis cell may be used for the oxidation and reduction of organic or inorganic components dissolved in the electrolyte.

Abstract: An electrolytic cell and electrolytic process for producing a metal by reduction of a metal oxide dissolved in a molten salt bath containing at least one chloride and at least one fluoride. A solid conductor of oxide ions is interposed between the anode and the cathode. The solid conductor preferably comprises zirconia, stabilized in cubic form by addition of a divalent or trivalent metal oxide such as yttria.

Abstract: Conductive ceramics are useful in the construction of electrochemical electrodes that are used in a wide variety of applications because of their inherent chemical resistance. When porous forms of these ceramics are employed as electrodes in even dilute corrosive solutions, corrosive ionic species are caused to diffuse from the solutions into the porous electrode and to concentrate in the vicinity of the electrical connection by means of electromigration. The resulting corrosive degradation of the electrode and the electrical connection ultimately causes electrical failure. The present invention uses polymers to impregnate and selectively coat the ceramic so as to create a barrier seal against the migration of corrosives into the electrode while allowing the ceramic electrode to maintain electrical contact with its environment. Methods for achieving such impregnation are disclosed.

Abstract: Metal nitride, carbonitride, and oxycarbonitride powder with high surface area (up to 150 m2/g) is prepared by using sol-gel process. The metal organic precursor, alkoxides or amides, is synthesized firstly. The metal organic precursor is modified by using unhydrolyzable organic ligands or templates. A wet gel is formed then by hydrolysis and condensation process. The solvent in the wet gel is then be removed supercritically to form porous amorphous hydroxide. This porous hydroxide materials is sintered to 725° C. under the ammonia flow and porous nitride powder is formed. The other way to obtain high surface area nitride, carbonitride, and oxycarbonitride powder is to pyrolyze polymerized templated metal amides aerogel in an inert atmosphere. The electrochemical capacitors are prepared by using sol-gel prepared nitride, carbonitride, and oxycarbonitride powder. Two methods are used to assemble the capacitors.

Abstract: Water-derived fuel gas. An underwater carbon arc operated in the absence of hydrocarbons results in a mixture of gases, being non-self-combustible but combustible as a fuel gas in the presence of air, and comprising gaseous hydrogen in major amount and carbon oxides in minor amount, predominantly carbon monoxide. The fuel gas is adapted along with air to run an internal combustion engine, and along with oxygen to operate a cutting or welding torch.

Abstract: Amorphous carbon comprising a dispersion comprising a catalytically effective load of catalyst, preferably an electrocatalytically effective load of a noble metal electrocatalyst, and membrane electrode assemblies and fuel cell electrodes incorporating same.

Abstract: An electrochemical cell for the production of fluorine includes an anode having a carbon portion partially or fully impregnated with a polymeric material and a conductive centrally disposed internal channel that permits the anode to be run at high current with uniform current densities without undue resistance heating.

Abstract: Carbon-containing components of cells for the production of aluminium by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: The sensor electrode has a sensing surface intended to contact a liquid medium for continuous measuring, in combination with a counter electrode and a reference electrode, of the hydrogen peroxide concentration over a concentration range from 0.005 mole/liter to 3 mole/liter, said sensor consisting of a carbon electrode having an open circuit potential between -65 and -85 mV, said open circuit potential being measured with respect to a Ag/AgCl/saturated Cl.sup.- reference electrode in an alkaline solution having a pH between 10.5 and 14, said solution containing hydrogen peroxide at a concentration of more than 0.5 mole/liter.

Abstract: A gas diffusion layer for a solid polymer electrolyte fuel cell having a solid polymer electrolyte and a catalyst layer disposed adjacent to the solid polymer electrolyte, where the gas diffusion layer includes a carbon fiber woven cloth having a surface and a coating of a fluororesin (such as polytetrafluoroethylene) containing carbon black on the surface, wherein the carbon fiber woven cloth is adapted to be disposed in the solid polymer electrolyte fuel cell such that the coating is adjacent to the catalyst layer in the solid polymer electrolyte fuel cell. Preferably, the coating penetrates no more than one-half the thickness of the carbon fiber woven cloth. Most preferably, the coating penetrates no more than one-third the thickness of the carbon fiber woven cloth. The carbon fiber woven cloth may be pre-treated with a water-repellent fluororesin (such as polytetrafluoroethylene), or with a mixture of a fluororesin and carbon black, to enhance water repellency.

Abstract: An electrolytic reduction cell for production of a metal includes an outer steel shell, a layer of insulating material adjacent the outer steel shell and a carbonaceous layer overlaying the insulating material and protecting the insulating material from an electrolytic bath to be contained in the cell. The carbonaceous layer includes at least one carbonaceous cathode block having an upper surface and a lower surface, with a plurality of electrical contact plugs being mounted in electrical contact with the lower surface of the cathode block. A collector plate is in electrical contact with the electrical contact plugs. The electrical contact plugs are distributed over the lower surface of the cathode block such that in operation of the cell, a substantially isopotential surface is achieved at the top surface of the cathode block.

Abstract: An electrode comprising a carbon material with a solid carbon skeleton network and a capacitor containing same, in which there is a first and a second plurality of pores forming transport channels and the first plurality of pores have a pore size of less than 10 nm.

Abstract: There is provided a concentration sensor for measurement of concentrations of one or plural target substances in a system, with a detection electrode of conductive diamond. The measuring method with the concentration sensor involves measuring the reaction potentials of plural target substances in a sample containing and determining the concentrations of the plural substances by use of the difference between the resulting reaction potentials of the respective substances. The measuring method can also determine the concentration of a single substance in a sample containing one kind of target substance.

Abstract: Gas Diffusion Electrodes (GDES) play a pivotal role in clean energy production as well as in electrochemical processes and sensors. These gas-consuming electrodes are typically designed for liquid electrolyte systems such as phosphoric acid and alkaline fuel cells, and are commercially manufactured by hand or in a batch process. However, GDEs using the new electrolytes such as conductive polymer membranes demand improved electrode structures.This invention pertains to GDEs and gas diffusion media with new structures for systems using membrane electrode assemblies (MEAs), and automated methods of manufacture that lend themselves to continuous mass production Unexpected improvements in gas and vapor transport through the electrode are realized by incorporating a new dispersion process in the construction, reformulating the applied mix with solution additives, and creating a novel coating structure on a conductive web.

Abstract: This invention covers a cathodic element free from asbestos fibres that can be obtained by deposition after filtration through a porous medium of an aqueous suspension comprising electrically conductive fibres, at least one cationic polymer, at least one electocatalytic agent, at least one pore-forming agent and at least one binder selected from among the fluoropolymers. The invention also covers a method for preparing such a cathodic element.

Abstract: A carbon-reinforced electrode is disclosed. The electrode is formed from a high surface area absorptive material ("HSAAM electrode") made from resorcinol, formaldehyde, a carbon reinforcing agent, a catalyst, and reaction products thereof, and is in a carbonized form. This electrode removes ions from a liquid when an electric current is applied. The liquid may be passed through a thickness of the electrode, or may be passed by the surface of the electrode. A method of making the HSAAM electrodes is also disclosed. The HSAAM electrodes are formed from setting a polymerized mixture of resorcinol, formaldehyde and a carbon reinforcing agent supplied in the form of carbon fibers, carbon felt or cellulose under controlled temperature and time constraints, and subsequently firing the resulting product so as to carbonize the electrode.

Abstract: The invention concerns a diaphragm chlor-alkali electrolysis cell comprising a cover, a conductive base for supporting the anodes and a cathode in the form of a box provided with internal wall, external wall and tubular fingers made of a mesh or perforated sheet covered with a porous diaphragm. One or more copper sheets for electric current distribution are fixed to the cathode external walls. The connection between the copper sheets and the cathode external walls is made by means of bolts with the interposition of a conductive and deformable element provided with residual elasticity under compression. The weldings for the assembling of the cathode walls are free from internal stresses.

Abstract: An electrolytic cell for the electrowinning of aluminium from alumina dissolved in a halide-containing molten electrolyte, has a cathode cell bottom made of a series of carbon cathode blocks (10) connected side-by-side by glue or ramming paste, each one provided with steel or other conductive bars (11) for the delivery of current and a series of anodes (15) facing the cathode cell bottom. The tops of the carbon blocks (10) forming the cathode cell bottom are shaped in such a way as to provide in the cell bottom a series of parallel channels (25) or grooves preferably coated with an aluminium-wettable refractory coating (35) covered in use by a pool (40) of molten aluminium or a layer of molten aluminium forming a drained surface. Movement of the aluminium pool (40) is decreased, cell operation improved and cell life extended.

Abstract: A high performance electrochemical cell is useful for recovery of metal from aqueous solutions. The electrochemical cell has a cathode assembly that includes a nonporous support member, a primary cathode, and a nonconductive or conductive porous material covering the primary cathode. An anode is spaced apart from the cathode assembly. Fluid is caused to flow through the porous material to the primary cathode, through openings or fluid collection channels in the nonporous support member, and uniformly out of the cell. Uniform and efficient deposition of metal is accomplished over the entire primary cathode because of modulation of fluid flow and increased mass transfer.

Abstract: A stacked plate cell having serially connected stacked electrodes is described, at least one stacked electrode consisting of a graphite felt plate, a carbon felt plate, a web having a carbon-covered starting material contact surface or a porous solid having a carbon-covered starting material contact surface or comprising such a material.

Abstract: A catalyst composition for use in a rechargeable metal-air electrochemical cell comprises an oxygen evolution catalyst coated with a thin film deposition of carbon. This catalyst is useful to make an air electrode which produces more power in a metal-air cell then a metal-air cell having oxygen evolution catalyst without the thin carbon film.

Abstract: The invention is directed to polymer thick film conductor compositions comprising conductive metal particles selected from the group consisting of finely divided powders of platinum group metals and mixtures thereof; modified graphite; and a thermoplastic polymer and optionally, graphite and/or a metallized graphite in combination with a surfactant may replace the modified graphite.

Abstract: Bipolar plate made of a composite material for use in a filter-press electrolyzer. Said plate comprises a central portion (6) which is electrically conductive and is obtained by heat-pressing of a mixture of graphite or conductive carbon and a thermoplastic polymer powder resistance to corrosion and two terminal portions (7,8) containing the distribution holes (2,3,4,5) for the inlet of the fresh electrolytes and for the outlet of the exhausted electrolytes and electrolysis products. Said terminal portions are integral with the central portion and are obtained during said heat-pressing from a mixture of graphite or conductive carbon and said thermoplastic polymer powder with a ratio between said powders lower than that of the central portion. Said mixture of the terminal portions may further contain also a non-conductive compound powder, in which case the mixture may also be free from graphite or conductive carbon powder.

Abstract: Two types of HgO-modified electrodes are disclosed. The HgO-modified electrode according to the present invention comprises, HgO particles as precursor of mercury, which can be exposed on the surface of the said electrode and then can be reduced electrochemically into micro-droplets of mercury; and electro-conductive material to maintain optimal conductivity of the said modified electrode. In the HgO-modified electrode according to the present invention, built-in mercury precursor, HgO can be utilized feasibly for the generation of the surface mercury droplets by in situ electrochemical treatment or pretreatment without necessity of Hg.sup.2+ solution. The electrode surface can be renewed easily either by a simple polishing process for the bulk-modified electrode type-I or by simple exchange for the screen-printed disposable type modified electrode type-II. So further simplification of anodic stripping analysis process is possible by employing the HgO-modified electrodes according to the present invention.

Abstract: The present invention describes an improved electrode suitable for application in solid polymer electrolyte fuel cells, comprising a thin, porous, planar, conductive substrate having one side coated with a pre-layer consisting of conductive carbon having a low surface area mixed to a first hydrophobic agent, to which is applied a catalytic layer consisting of platinum supported on conductive carbon with a high surface area, mixed to a second hydrophobic agent. The hydrophobic degree of the applied layers are suitably adjusted to obtain the best exploitation of the catalyst and to improve the water balance of the process.

Abstract: This invention provides apparatus and a method for measuring the concentration of alumina in a molten electrolyte in a smelter. A test anode (101) (a mimic of the actual cell anode) supplied from a computer-controlled voltage source (303) with several to about (100) rapid cyclic voltammetry sweeps the voltage at which the anode effect occurs, as sensed by current measurement (305). In order to derive a measurement the voltage is compared within the computer (301) to previous measurements made from a calibration set of alumina samples in known concentrations. Brief rapid cycles and an improved electrode configuration help to provide results from the invention which are reproducible and accurate, and in addition the test electrode has a long life.