Abstract: A massive anode is assembled from many, closely packed modular anodes. Although close-packed, the modular anodes are nevertheless spaced apart one from the other. The massive anode has at least substantial inflexibility. It can be particularly useful where a flexible cathode may move toward, and even contact, the anode, e.g., in electrogalvanizing where a moving sheet from a metal coil being coated may thump against the anode. The individual modular anodes provide a collective, generally planar front face toward the cathode. Individual, adjacent modular anodes can be separated at least in part by dielectric spacing members which have portions extending toward the cathode, thereby initially receiving any impact from the cathode.

Abstract: Renewable modified composite electrodes for electrochemical application are provided by homogeneous structure of a conductive filler disposed in a polymeric matrix or binder containing a modifier in the polymer chain. The modifier provides distinctive characteristics of electroactivity, inclusion, acidic/basic, complexing/chelating or electrocatalysis to the surface of the electrode in a solution. After use, the electrode may be renewed by removing a surface portion and thereby exposing a fresh portion of the homogeneous structure.

Abstract: A platinum black air cathode has an active layer and a support layer. The active layer comprises platinum black plus hydrophobic binder, typically a fluorinated polymer. The support layer may be made up from carbon black bound with a halopolymer binding agent. Such combination can provide for economical utilization of active ingredient without sacrifice of cathode structural integrity. To assist in this structural integrity, a thin support mesh may be used, preferably with the support layer. There can also be employed between the active layer and the support layer a porous bonding layer, which can find broader utilization with layered gas diffusion electrodes in general. For highly desirable, greatly extended operation of the platinum black air cathode, the cathode can be operated intermittently, or anodically polarized or be subjected to infrequent voltage suppression, as well as being involved with any combination of the foregoing.

Abstract: An electrode is provided which is formed by the metallurgical bonding technique of diffusion bonding the backplate, conductor elements and electrode surface together, then applying the catalytic coating to the electrode surface, and bonding the backplate to an electrical conducting plate.

Abstract: Monopolar, bipolar, and hydrid filter press electrolytic cells for electrolytic processes utilizing a novel method of introducing and removing electrical energy are disclosed. The invention contemplates a novel low pressure, high surface contact area connecting means for joining the anode element and cathode element of electrode assemblies. The invention also contemplates a low pressure, high surface contact area contact of the current distributor member to the back plate.

Abstract: An electrolytic cell for the reduction of solutions containing both titanium and iron ions, e.g., solutions emanating from the sulfuric acidulation of ilmenite, has a cationic exchange membrane separating the anode and cathode compartments thereof; the solutions to be reduced are circulated within the cathode compartment of said electrolytic cell.

Abstract: A process is described for preparing quaternary ammonium hydroxides of improved purity. In one embodiment, the present invention relates to a process of preparing quaternary ammonium hydroxides from the corresponding quaternary ammonium salts in an electrolytic cell which comprises an anolyte compartment containing an anode and a catholyte compartment containing a cathode and water, said anolyte and catholyte compartments being separated from each other by a cation-exchange membrane, said process comprising the steps of(a) providing the catholyte compartment with a cathode of zinc, cadmium, tin, lead, or alloys thereof, mercury, or mercury amalgam,(b) charging an aqueous solution containing a quaternary ammonium salt to the anolyte compartment,(c) passing a current through the electrolytic cell to produce quaternary ammonium hydroxide in the catholyte compartment, and(d) recovering the quaternary ammonium hydroxide from the catholyte compartment.

Abstract: A carbon anode for a fluorine-producing cell is doped with a very fine dispersion of one or more transition metals, preferably nickel, vanadium and/or cobalt. The transition metal may be dispersed within the particles and/or the binder and is conveniently introduced in the form of an organic complex of the transition metal which decomposes during heat treatment of the consolidated mass of particles and binder.

Abstract: A composite hydrogen purification membrane comprises an anode for hydrogen oxidation, a cathode for hydrogen reduction, with a proton conductor disposed between and in contact with the anode and the cathode. Electrons are conducted between the anode and cathode through an external connection, with the electron flow generated by the difference in hydrogen partial pressure between the anode and cathode sides of the membrane. Thus the composite hydrogen purification membrane provides high hydrogen permeability and selectivity relative to the impurities in a feed gas, producing pure hydrogen without requiring an external voltage source.

Abstract: A system for treating a barren solution typically containing a heavy metal such as copper, and complexed cyanide, from a precious metal mill, is treated in a first electrochemical cell to remove the heavy metal and free the cyanide whereafter the treated solution can be returned to the precious metal mill as leaching solution; the barren solution flows through a porous cathode in which the heavy metal is electrochemically deposited, and against an inert anode; the deposited heavy metal is recovered in a sheet form by employing the heavy metal loaded cathode as an anode in a second electrochemical cell, the heavy metal entering solution and being deposited on a cathode sheet typically of stainless steel or titanium from which a deposited sheet of the heavy metal is readily peeled; the porous cathode free of heavy metal can be reused in the first cell.

Abstract: The process for the manufacture of cathodes suitable for use in electrolysis comprising depositing onto an electrically conductive substrate at least one layer of said Group VIII metal salts, one of which is a platinum group metal and then subjecting the whole to a heat treatment to oxidize said salts to the oxide form.

Abstract: A process for electrochemical reduction of CO.sub.2 to CH.sub.4 and C.sub.2 H.sub.4 providing both high current densities and high Faradaic efficiencies. The process is carried out in an electrochemical cell wherein copper is electrodeposited in situ on the cathode surface making freshly deposited copper available for the electrochemical reduction. Faradaic efficiencies of about 75 to about 98 percent for production of CH.sub.4 and C.sub.2 H.sub.4 are obtained.

Abstract: A pressure-molded, rigid, high surface cathodic or anodic electrode of low electrical resistance and good mechanical strength and resistance to corrosion comprising non-dissolving, electrically-conducting metal particles of high specific surfaces and fractal structure which are bound with up to 15% by weight of aluminum phosphate.

Abstract: A cathode for electrolytic refining or electro-winning of copper is disclosed. The cathode comprises a steel hanger bar having a copper cladding and a flat stainless steel starter sheet with a plurality of lugs formed along its upper edge secured to the hanger bar. Alternating lugs are bent, in opposite directions to abut and engage the side faces of the copper-clad hanger bar and are welded to the copper cladding. The lugs can be welded to the bar upper face or to the bar side faces and may have a stainless steel strip explosion bonded to the copper cladding interposed between the lugs and the copper cladding for welding of the lugs to the stainless steel strip.

Abstract: A conductive silver/silver chloride composition consisting essentially of:(a) about 6 to about 10.5 parts by weight of a vinylidene chloride thermoplastic polymer having a glass transition value of above about 100.degree. F.;(b) at least a sufficient amount of an organic solvent capable of dissolving polymer (a);(c) about 47 to about 57 parts by weight of silver flake; and(d) about 8 to about 16 parts by weight of silver chloride.

Abstract: A highly durable cathode of a low hydrogen overvoltage with particles of an electrode active metal being stuck on the core material of the electrode, wherein a part or all of the electrode active metal particles is a hydrogen absorbing metal which is capable of electro-chemically absorbing and desorbing hydrogen.

Abstract: Cermet electrode compositions and methods for making are disclosed which comprise NiO--NiFe.sub.2 O.sub.4 --Cu--Ni. Addition of an effective amount of a metallic catalyst/reactant to a composition of a nickel/iron/oxide, NiO, copper, and nickel produces a stable electrode having significantly increased electrical conductivity. The metallic catalyst functions to disperse the copper and nickel as an alloy continuously throughout the oxide phase of the cermet to render the electrode compositon more highly electrically conductive than were the third metal not present in the base composition. The third metal is preferably added to the base composition as elemental metal and includes aluminum, magnesium, sodium and gallium. The elemental metal is converted to a metal oxide during the sintering process.

Abstract: An apparatus for the galvanic reinforcement of an automotive trace on a glass pane, especially a motor vehicle glass pane, has an elongated housing adapted to enclose the trace and spaced uniformly from opposite longitudinal edges thereof. The electrolyte and a rinsing liquid can be passed uniformly through this chamber within which a anode extends in juxtaposition with the trace which is poled as a cathode. Between the anode and the cathode an electrodeposition current is passed to deposit metal from the electrolyte onto the trace.

Abstract: The invention is an article comprising at least partially a catalytic, metal-containing, electrically conducting coordination polymer. In addition, this invention includes a process of manufacturing the article comprising applying a mixture containing a catalytic, metal-containing, electrically conducting coordination polymer to a substrate and drying said fluid to form a coating. This invention also encompasses an electrolytic cell comprising a cell body and a cathode spaced apart from an anode, said anode comprising a catalytic, metal-containing, electrically conducting coordination polymer. Another aspect of this invention is a process for generating reduction-oxidation reaction products comprising electrolyzing a solution in the above described electrolytic cell.

Abstract: A highly active powder catalyst with a high concentration of platinum group elements prepared from an amorphous alloy consisting of at least one of valve metals, at least one of platinum group elements and balance being at least one element selected from Ni and Co by immersion in a hydrofluoric acid, and a highly active electrode prepared by using the above mentioned powder catalyst.

Abstract: The anode comprises a core of a metal having a negative potential relative to steel, and an adjacent electrode of a material having a positive potential relative to steel. The adjacent electrode has a first substrate generally facing the core and a second substrate in direct electrical communication with the first substrate end of a material having a negative potential relative to steel substantially shielded from the core by the first substrate. The anode includes a suitable porous material between the core and the electode which tends to retain water. The anode produces a potential voltage in the presence of an electrolyte between the core and electrode which is the collective effect of the material of the core and the materials of the electrode. Such an anode can produce a higher potential voltage than conventional sacrificial anodes and be designed for particular desired voltage potentials.

Abstract: An electrode, and method of producing same, including tungsten which has been heated in wet hydrogen at 1050.degree. C. for 5 to 10 minutes, then heated at about 1500.degree. C. for about three hours in a vacuum, and then further heated at about 2800.degree. C. for about 5 minutes in a vacuum.

Abstract: The permanganate process for treating plastics, e.g., printed circuit boards, to enhance the adhesion of metal plating to the plastic is improved by employing electrolysis to either maintain a certain permanganate level in the operating bath or to regenerate a spent or used bath.

Abstract: A method and apparatus for refining elemental sulphur and hydrogen gas from H.sub.2 S is disclosed. More specifically, the present invention relates to a method and apparatus for vapor phase electrolysis of H.sub.2 S gas using a molten polysulfide electrolyte disposed in a matrix.

Abstract: A silver recovery cell for devices recovering silver from silver laden solutions, the silver recovery cell permitting visual inspection of the condition of plated silver within the cell. A clear canister is provided having an anode rod centrally connected thereto at its bottom. A cathode cylinder coaxially surrounds the anode rod; the cathode cylinder has a longitudinal slot. Terminals through the clear canister are provided for both the anode rod and the cathode cylinder in order to connect a conventional electrical power supply therewith. A removable top is further provided having inlet and outlet passageways for the silver laden solution to enter the leave the clear canister. An inlet port constrictor is provided to speed up fluid flow of the silver laden solution into the clear canister. In operation, a user may view the status of silver plating by merely looking through the clear canister and the slot in the cathode cylinder. A light may be provided in the top to facilitate visual inspections.

Abstract: Tungsten-titanium sputtering targets with improved characteristics are made from high-purity tungsten powder and a second powder consisting of high-purity titanium hydride powder or high-purity titanium hydride powder and high-purity titanium powder. The second powder contains at least 5%, preferably 25% to 100% by weight of titanium hydride powder. A powder mixture having a binodal particle size distribution with respect to the tungsten and second powders is placed under a containment pressure in a die. The die is heated in a vacuum hot-press chamber to a temperature sufficient to dehydride the titanium hydride, and to remove gases and alkali metals. The die is then heated to a second temperature in the range of 1350.degree. to 1550.degree. C. while maintaining the containment pressure and vacuum. A compaction force in the range of 2000 to 5000 psi is then applied to form a compact. The compaction force and vacuum are subsequently released and the compact is cooled.

Abstract: An efficient electrolytic recovery system, having several safety mechanisms, for recovering precious metals from a liquid medium is described. The system includes at least oen electrolysis cell unit having a plurality of reticulate metal foam cathodes. The system of the invention will efficiently recover such precious metals as Au, Ag and Pt. The system may also include a pH adjust means and a means for oxidizing cyanide in the liquid medium.

Abstract: Apparatus, which can be a pulsed column, which functions as an efficient electrolytic cell having an efficient liquid-liquid extraction capability. The apparatus can comprise an anode/cathode assembly having a geometry such as to produce a substantially uniform current distribution across the cell.

Abstract: The invention concerns a process for the electrolytic preparation of a mother alloy of iron and neodymium by the reduction of a mixture comprising at least one reactive oxygen-bearing compound of neodymium in a bath of molten halides with at least one metallic cathode, preferably of iron, and a carbon anode. In accordance with the invention, the bath is primarily formed by a mixture of molten fluorides whose decomposition potential is close to that of NdF.sub.3 or more negative, such as for example NdF.sub.3, MgF.sub.2, ScF.sub.3, CeF.sub.3, LaF.sub.3, BaF.sub.2, CaF.sub.2 and SrF.sub.2, and permitting solubilization of the oxides by a complexing effect, the solute to be reduced is formed by a mixture of salts primarily containing a reactive oxygen-bearing compound of neodymium which is very rapidly soluble in the molten electrolyte. The working temperature is in a range of from 640.degree. to 1030.degree. C., the anodic current density is from 0.1 to 1.5 A/cm.sup.

Abstract: Sputtering targets are made by melting at least one rare earth and at least one transition metal to produce an amorphous alloy melt, forming a powder of the alloy in an oxygen free atmosphere, introducing the powdered alloy into a reducing mold, adding a layer of powdered oxygen-getter on top of the powdered alloy, and hot pressing the alloy.

Abstract: There is described a simple two compartment electrochemical cell which may be associated in multiples in parallel for electrochemically freeing alkanolamines of the heat stable salt forming anions found or formed in acid gas conditioning thermal regenerative sorbent processes using alkanolamines as sorbents for acid gases, the cell having an anion exchange membrane separating the cell into two compartments and an anode comprised of an iridium coated electroconductive metal electrode.

Abstract: A method of producing high purity aluminum-lithium mother alloys essentially free from sodium, potassium and calcium, which comprises electrolyzing mixed molten salts consisting essentially of lithium chloride and potassium chloride preferably under a cathodic current density in the range of 0.005 to 1 A/cm.sup.2, using one or more hollow cylindrical solid aluminum cathodes, and thereby producing an aluminum-lithium alloy on the cathodes. In the method, the mixed molten salts may be composed essentially of 34 to 64 wt. % of lithium chloride and 66 to 36 wt. % of potassium chloride, and, optionally, 1 to 20 wt. % of sodium chloride based on a combined weight of the aforesaid two components. Preferably, throughout the electrolysis, the potential difference between the cathode and a two-phase (.alpha.+.beta.) aluminum-lithium alloy reference electrode is continuously measured and differentiated with respect to time and at the point of a sudden change in the differentiated value, the electrolysis is stopped.

Abstract: There is described a simple two compartment electrochemical cell which may be associated in multiples in parallel for electrochemically freeing alkanolamines of the heat stable salt forming anions found or formed in acid gas conditioning thermal regenerative sorbent processes using alkanolamines as sorbents for acid gases, the cell having an anion exchange membrane separating the cell into two compartments and an anode comprised of platinum or a platinum coated electroconductive metal electrode.

Abstract: An apparatus and method are disclosed for the selective electrochemical polishing of a lateral tip of a deep longitudinal notch in a work piece used to test crack initiation properties of materials. A DC power source is connected to the work piece and to an electrode disposed laterally along the distal end of an insulated body which is inserted in the longitudinal notch. The electrode and distal end of the body are disposed along the tip of the notch, but are spaced from the notch so as to provide a lateral passage for an electrolyte. The electrolyte is circulated through the passage so that the electrolyte only contacts the work piece adjacent the passage. Conveniently, the electrolyte is circulated by use of an inlet tube and an outlet tube provided at opposite ends of the passage. These tubes are preferably detachably located adjacent the ends of the passage and suitable seals are provided.

Abstract: A process and apparatus for electrochemically separating alkali oxides to simultaneously generate oxygen gas and liquid alkali metals in a high temperature electrolytic cell is provided. The high temperature electrolytic cell comprises a cathode in contact with an alkali ion conducting molten salt electrolyte separated from the anode by an oxygen vacancy conducting solid electrolyte. Alkali metals separated in the alkali metal reducing half cell reaction are useful as reducing agents in the direct thermochemical refining of lunar metal oxide ores to produce metallic species and alkali oxides, and the alkali oxides may then be recycled to the high temperature electrolytic cell.

Abstract: Apparatus for reducing oxalic acid to a product includes a cell. A separator which separates the cell into two chambers; a catholyte chamber and an anolyte chamber. Each chamber has an inlet and an outlet. A porous cathode having a catalyst is arranged within the catholyte chamber so that a catholyte entering the inlet of the catholyte chamber will pass through the cathode. A porous anode is arranged within the anolyte section so that an electrolyte entering the inlet of the anolyte section will pass through the anode and exit through the outlet of anolyte section. A source provides the catholyte which is a mixture of oxalic acid and an electrolyte to the inlet of the catholyte chamber while another source provides the electrolyte to the inlet of the anolyte chamber. A d.c. voltage is provided between the cathode and the anode so as to cooperate in the reduction of oxalic acid within the porous cathode to a product which exits the catholyte chamber by way of its outlet.

Abstract: A highly durable cathode of a low hydrogen overvoltage with particles of an electrode active metal being stuck on the core material of the electrode, wherein a part or all of the electrode active metal particles is a hydrogen absorbing metal which is capable of electro-chemically absorbing and desorbing hydrogen.A method for manufacturing a highly durable cathode of a low hydrogen overvoltage, characterized in that an electrode core is immersed in a plating bath with particles of a hydrogen absorbing metal capable of electro-chemically absorbing and desorbing hydrogen being dispersed as at least one part of particles of an electrode active metal, and that the electrode active metal particles are electrolytically co-deposited on the electrode core together with a plating metal by the composite plating method.

Abstract: Nickel alloy anodes are suitable for electrochemical cells that are used for the selective replacement of chlorine in organochlorine compounds with hydrogen and are resistant to corrosion. Electrochemical cells containing Hastalloy C-276 anodes and silver cathodes, for example, are used to convert tetrachloropicolinic acid to 3,6-dichloropicolinic acid.

Abstract: Method for the electrolytic preparation of hypochlorite in flowing salt-containing water for the purpose of disinfecting swimming baths, massage baths, drinking water etc. by means of an electrolysis reactor comprising a "scale-retarding" cathode having an open structure and a specific surface of at least 10 cm.sup.2 /cm.sup.3.

Abstract: An anode configuration is provided particularly for a bath that is used for electrolytically plating a substrate with a nickel and/or cobalt phosphorus alloy. The anode comprises a plurality of widely spaced portions of material, preferably of platinum or rhodium. The anode configuration is such that the anode has a very high current density in use--at least 200 amperes per square foot and preferably 500 amperes per square foot. The wide spacing of the anode portions may be provided in a number of different ways. A platinum wire may extend between titanium screws attached to a pair of parallel spaced titanium buses, in a zig-zag manner. A platinum wire may be welded at its opposite ends to a titanium bus, and helically wrapped around the bus, with the welding junctions covered by an insulating material (e.g. vinyl). A platinum tube may be shrink fit onto a titanium bus.

Abstract: Cathode for use in magnesium production by electrolysis of molten salts. The cathode consists of compact molybdenum, tungsten or alloys of these metals or consists of a substrate coated with molybdenum, tungsten or alloys of these metals. The thickness of the coating is at least 10-20 .mu.m. The substrate can be iron or carbon. Carbon coated with molybdenum, tungsten or alloys of these metals can be used as the cathodic face of a bipolar electrode. The wetting of the cathode by magnesium is improved and the amount of contaminants in the produced metal is reduced.

Abstract: The invention is a vertically disposed electrolytic cell comprising:a hollow, cylindrically shaped recycle tube;a hydraulically permeable, hollow, cylindrically shaped cathode concentric with and surrounding said recycle tube to define a first annular space therebetween;a hydraulically permeable, hollow, cylindrically shaped anode concentric with and surrounding said cathode to define a second annular space therebetween; anda hollow, cylindrically shaped, ion permeable membrane positioned in said second annular space concentric with said cathode and said anode, said membrane dividing the second annular space into an anode compartment containing the anode and a cathode compartment containing the cathode.The invention includes a method for operating the apparatus.

Abstract: A cathode suitable for use in an electrochemical process evolving hydrogen (for example the chloralkali process) in which the cathode comprises an electrically conductive substrate (1) made of a non-ferrous metal or having a coherent coating of non-ferrous metal on which is provided an electrocatalyst (4) comprising platinum and ruthenium and wherein the cathode is made more poison-resistant by a deposition of gold or silver and, optionally, a further deposition of PTFE. The cathode is particularly resistant to poisoning by iron.

Abstract: A gas and electrolyte permeable metal layer is bonded to an ion-permeable membrane by electroless deposition to produce a permeable metal deposit upon the membrane or diaphragm. Advantageously, the membrane surface to be coated is pretreated with an amphoteric material. Thereafter, the treated surface is treated to deposit the coating. Typical metals deposited include platinum group metals, iron group metals, such as nickel, cobalt and others including gold and silver. The coatings are very thin, rarely in excess of about 50 to 100 microns.The coated membrane may be installed in an electrolytic cell used for producing chlorine and alkali by electrolysis of alkali metal chloride with the coating serving as one electrode and another opposed electrode on or adjacent to the opposite side of the membrane. It may also be used in water electrolysis and for other purposes.The coatings may be thickened by depositing other coatings of the same or different composition by suitable coating techniques.

Abstract: A method of making a cathode suitable for an electrochemical cell of the type having a molten sodium anode, a beta"-alumina separator, and a cathode which comprises one or more transition metals selected from the group comprising Fe, Ni, Co, Cr and Mn. The method comprises heating a particulate starting material comprising at least one member of the group of transition metals in an oxidizing atmosphere to cause its particles to become at least partially oxidized, and to adhere together to form a unitary porous matrix. This matrix is then heated in a reducing atmosphere at least partially to reduce the oxide formed during the formation of the matrix, and the reduced matrix is then impregnated with a sodium aluminium chloride molten salt electrolyte. Sodium chloride in dispersed form is incorporated into the matrix, preferably by mixing sodium chloride in particulate form with the particulate transition metal starting material, before the heating in an oxidizing atmosphere to form the matrix.

Abstract: This invention is directed to an electrode unit to be used for purification of emulsions and polluted waters, especially oil-bearing waters, by electrolysis which comprises vertically placed adjacent electrode plates of a soluble material, spacers for adjusting the distance between the electrode plates and equipment for adjusting the depth of immersion of the electrode plates. The tips of the electrode plates defines the only area of the plates in contact with the liquid to be purified and the depth of immersion of the electrode plates is adjusted in order to keep the current density between the electrode tips within a desired area. In addition, the space in between the plates is also adjusted in order to keep the current density between the electrode tips within the desired area.

Abstract: A device for silverizing running water and an electrode therefor are formed so that the electrode has a curved guide provided on its one surface and a plurality of through-going openings located outside of the curved guide, to direct water to be silverized from inside of the curved guide to its outside and then through the openings.

Abstract: Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.

Abstract: An electrode for electrolysis which comprises an electrode substrate made of a conductive metal having thereon a coating of an electrode active substance is disclosed, in which a first intermediate layer comprising at least one compound of rare earth element and a second intermediate layer containing at least one of base metals and base metal oxides are provided between said electrode substrate and electrode active substance coating. The electrode exhibits high resistance to passivation and excellent durability, and is particularly suitable for use in electrolysis accompanied by oxygen generation and for organic electrolysis.

Abstract: An improved multiple layered porous electrode for use in an electrochemical membrane cell is provided having a first perforated support layer, a second layer of fibers, a third layer of fibers less dense than the second layer and a fourth layer of meshed wire cloth.