Barium electrodes

This reference reports the appearance of a light-induced potential difference between two electrodes separated by a specially organized molecular multilayer. A barium electrode and a semitransparent aluminium electrode, which have substantially different electronic work functions JAl > c/Ba, have been used in these studies. The two electrodes were separated by a multilayer system consisting of a layer of isolating molecules covered by a... 

Barium fluoride is used commercially in combination with other fluorides for arc welding (qv) electrode fluxes. However, this usage is limited because of the availabiUty of the much less expensive naturally occurring calcium fluoride. 

The most significant commercial product is barium titanate, BaTiO, used to produce the ceramic capacitors found in almost all electronic products. As electronic circuitry has been rniniaturized, demand has increased for capacitors that can store a high amount of charge in a relatively small volume. This demand led to the development of highly efficient multilayer ceramic capacitors. In these devices, several layers of ceramic, from 25—50 ]lni in thickness, are separated by even thinner layers of electrode metal. Each layer must be dense, free of pin-holes and flaws, and ideally consist of several uniform grains of fired ceramic. Manufacturers are trying to reduce the layer thickness to 10—12 ]lni. Conventionally prepared ceramic powders cannot meet the rigorous demands of these appHcations, therefore an emphasis has been placed on production of advanced powders by hydrothermal synthesis and other methods. 

Paste Mixing. The active materials for both positive and negative plates are made from the identical base materials. Lead oxide, fibers, water, and a dilute solution of sulfuric acid are combined in an agitated batch mixer or reactor to form a pastelike mixture of lead sulfates, the normal, tribasic, and tetrabasic sulfates, plus PbO, water, and free lead. The positive and negative pastes differ only in additives to the base mixture. Organic expanders, barium sulfate [7727-43-7] BaSO carbon, and occasionally mineral oil are added to the negative paste. Red lead [1314-41 -6] or minium, Pb O, is sometimes added to the positive mix. The paste for both electrodes is characterized by cube weight or density, penetration, and raw plate density. 

Electrolysis of acidified water using platinum electrodes is a convenient source of hydrogen (and oxygen) and, on a larger scale, very pure hydrogen (>99.95%) can be obtained from the electrolysis of warm aqueous solutions of barium hydroxide between nickel electrodes. The method is expensive but becomes economical... 

With respect to pH sensitivity and an adequate speed of response (time constant r = RC where R is the resistance of the measuring circuit and C the capacitance of the electrode), a certain degree of superficial swelling is needed however, the gel layer thus formed should remain thin in order to minimize the solubility of the glass and to guarantee sufficient durability of the electrode. In this respect lithium barium silicates offer an attractive compromise32. 

Many other heterogeneous electrodes have been developed based on, e.g., calcium oxalate or stearate in paraffin, barium sulphate in paraffin or silicone-rubber, bismuth phosphate or iron(III) phosphate in silicone-rubber, caesium dodecamolybdophosphate in silicone-rubber and amminenickel nitrate in phenol-formaldehyde resin39 these permit the determination, respectively, of Ca and oxalate, Ba and sulphate, Bi or Fe(HI) and phosphate, Cs, Ni and nitrate, etc. 

Building on the success of 37 in recognition of barium ions, this unit was incorporated into monomer units derived from pyrrole and EDOT (42, 43 and 44).113 Electrodes modified by the corresponding electrodeposited polymers showed an electrochemical response in the presence of Ba2+ which was similar to 37, albeit of a lesser magnitude. 

Lebel [224] has described an automated chelometric method for the determination of sulfate in seawater. This method utilises the potentiometric end-point method for back titration of excess barium against EDTA following precipitation of sulfate as barium sulfate. An amalgamated silver electrode was used in conjunction with a calomel reference electrode in an automatic titration assembly consisting of a 2.5 ml autoburette and a pH meter coupled to a recorder. Recovery of added sulfate was between 99 and 101%, and standard deviations of successive analyses were less than 0.5 of the mean. 

Barium B3CI2/B3CO3 BaS04 (s) 0 0 0 Low S04 level High running cost toxicity and solid waste affect electrode and membrane... 

Sulfates are precipitated as BaS04, and then reduced with carbon at 1,000°C to produce CO2 and CO. The CO is either measured directly or converted to CO2 by electrical discharge between platinum electrodes (LonginelU and Craig 1967). Total pyrolysis by continuous flow methods has made the analysis of sulfate oxygen more precise and less time-consuming than the off-line methods. Bao and Thiemens (2000) have used a C02-laser fluorination system to liberate oxygen from barium sulfate. 

Elemental composition Ba 72.52%, C 12.68%, N 14.79%. Barium metal can be analyzed by various instrumental and wet methods (see Barium). Cyanide ion in the aqueous solution of the compound may be determined by using a cyanide ion-specific electrode or by colorimetry using pyridine-barbituric acid reagent (APHA, AWWA, and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed., Washington, DC American Public Health Association). 

Elemental composition Ba 52.55%, N 10.72%, 0 36.73%. Barium may be determined by various instrumental techniques (see Barium). The nitrate ion can be determined by preparing an aqueous solution of the compound and analyzing by ion-chromatography, or nitrate ion-selective electrode. 

Highly pure lanthanum oxide is used to make optical glass of high refractive index for camera lenses. It also is used to make glass fibers. The oxide also is used to improve thermal and electrical properties of barium and strontium titanates. Other applications are in glass polishes carbon arc electrodes fluorescent type phosphors and as a diluent for nuclear fuels. In such apph-cations, lanthinum oxide is usually combined with other rare earth oxides. 

An example of the difficulties encountered when trying to fabricate an ohmic electrode, able to sustain a space-charge-limited current, is the recent work of the Neher group [179]. The authors deposited barium as an electron injection cathode on top of an electron transporting polymer based on a naphthalene diimide core whose LUMO is as low as 4 eV below vacuum level. Although the Fermi level of barium should be above the LUMO of the polymer, the electron current is. 

However, it can undergo self-reductive dissolution (loss of active material) accompanied by oxygen evolution [349]. The active material of the positive electrode (in pocket plate cells) consists of nickel hydroxide mixed with small additions of cobalt and barium hydroxides to improve the capacity and charging/discharging performance and graphite to improve conductivity [348]. 

Pr par( km,—l. By eleotrolysing moistened baric hydrate, carbonate, nitrate, or chloride, the negative electrode being meroury. An amalgam of barium is thus formed, om which the mercury is removed by distillation. 

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