Barium applications

Metal-recovery operations, phosgene in, 18 810-811. See also Metals recycling Metal reductions hydrazine, 13 569 to liquid metal, 16 141-146 Metal refining, 16 149-151 barium application, 3 349 limestone in, 15 38-39 Metal removal, in electrochemical machining, 9 593-595 Metal-rich phosphides, 19 59... 

It was pointed out in Section XIII-4A that if the contact angle between a solid particle and two liquid phases is finite, a stable position for the particle is at the liquid-liquid interface. Coalescence is inhibited because it takes work to displace the particle from the interface. In addition, one can account for the type of emulsion that is formed, 0/W or W/O, simply in terms of the contact angle value. As illustrated in Fig. XIV-7, the bulk of the particle will lie in that liquid that most nearly wets it, and by what seems to be a correct application of the early oriented wedge" principle (see Ref. 48), this liquid should then constitute the outer phase. Furthermore, the action of surfactants should be predictable in terms of their effect on the contact angle. This was, indeed, found to be the case in a study by Schulman and Leja [49] on the stabilization of emulsions by barium sulfate. 

Other Applications. Polyacrylamides are used in many additional appUcations including soil modification (138), dust control (139,140), humidity control (141), protein purification (142), removal of barium from wastewater (143), and removal of arsenic from hydrocarbons (144). Polyacrylamides have been used for many years in sugar manufacture and textile treatment. 

In other applications of CT, orally administered barium sulfate or a water-soluble iodinated CM is used to opacify the GI tract. Xenon, atomic number 54, exhibits similar x-ray absorption properties to those of iodine. It rapidly diffuses across the blood brain barrier after inhalation to saturate different tissues of brain as a function of its lipid solubility. In preliminary investigations (99), xenon gas inhalation prior to brain CT has provided useful information for evaluations of local cerebral blood flow and cerebral tissue abnormalities. Xenon exhibits an anesthetic effect at high concentrations but otherwise is free of physiological effects because of its nonreactive nature. 

Uses. Hiere are several different grades of barium carbonate manufactured to fit the specific needs of a wide variety of applications very fine, highly reactive grades are made for the chemical industry coarser and more readily haridleable grades are mainly supplied to the glass industry ... 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

For electrical insulation china clay is commonly employed whilst various calcium carbonates (whiting, ground limestone, precipitated calcium carbonate, and coated calcium carbonate) are used for general purpose work. Also occasionally employed are talc, light magnesium carbonate, barytes (barium sulphate) and the silicas and silicates. For flooring applications asbestos has been an important filler. The effect of fillers on some properties of plasticised PVC are shown in Figure 12.21 (a-d). 

Resoles are usually those phenolics made under alkaline conditions with an excess of aldehyde. The name denotes a phenol alcohol, which is the dominant species in most resoles. The most common catalyst is sodium hydroxide, though lithium, potassium, magnesium, calcium, strontium, and barium hydroxides or oxides are also frequently used. Amine catalysis is also common. Occasionally, a Lewis acid salt, such as zinc acetate or tin chloride will be used to achieve some special property. Due to inclusion of excess aldehyde, resoles are capable of curing without addition of methylene donors. Although cure accelerators are available, it is common to cure resoles by application of heat alone. 

The product crystals find industrial application as a component raw material for optical glass, fibreglass, Braun tubes, electric condensers, barium ferrite, etc. Needles shaped crystals are obtained at high pH, while pillar-shaped crystals are formed at neutral pH. The formation of carboxyl ions is via hydroxy ions at high pH, but at neutral pH it may accompany the production of hydrogen sulphide, as... 

Greases are also made from soaps of strontium, barium and aluminum. Of these, aluminum-based grease is the most widely used. It is insoluble in water and very adhesive to metal. Its widest application is in the lubrication of vehicle chassis. In industry, it is used for rolling-mill applications and for the lubrication of cams and other equipment subject to violent oscillation and vibration, where its adhesiveness is an asset. 

Discussion. The barium salt of chloranilic acid (2,5-dichloro-3,6-dihydroxy-p-benzoquinone) illustrates the principle of a method which may find wide application in the colorimetric determination of various anions. In the reaction... 

Application of the reaction to the 2-azidobenzoyl derivative of diethylene glycol monomethyl ether 92, in a mixture of tetrahydrofuran and diethylene glycol monomethyl ether as the nucleophile, affords 2-(2-methoxyethoxy)ethyl 2-[2-(2-methoxyethoxy)ethoxy]-37/-azepine-3-carbo-xylate (93), which displays metal cation complexing properties towards lithium, potassium, and. to a lesser extent, barium and calcium cations.198... 

Structural binder A wide range of applications in electronics makes use of the plastics as a structural binder to hold active materials. For example, a plastic such as polyvinylidene fluoride is filled with an electroluminescent phosphor to form the dielectric element in electroluminescent lamps. Plastics are loaded with barium titanate and other high dielectric powders to make slugs for high K capacitors. The cores in high frequency transformers are made using iron and iron oxide powders bonded with a plastic and molded to form the magnetic core. 

Neither Ca, Sr nor Ba metal has any structural integrity. The principal application of metallic Ca is as a reducing agent in the preparation of metals, such as Th and Zr. Like Mg, it can be used in the deoxidation and desulfurization of steels. Small quantities are used for alloying with Al and for the removal of Bi from Pb. Neither Sr nor Ba have any significant commercial uses. Barium is used to a limited extent as a getter to remove reactive gases from vacuum tubes. 

In the particular example shown, zinc sulfate and barium hydroxide are being dispensed into the test tube so as to precipitate the proteins. The filtrate obtained is the filtrate from 10 microliters of serum. This can be used for several purposes and in the application being referred to, an amount equivalent to 3 microliters is being used for sugar determination, by the hexokinase procedure and an amount equivalent to 3 microliters is being used for urea estimation with diacetylmonoxime (15). 

This latter point was stressed by some of us in a recent report studying NO storage and reduction on commercial LSR (lean storage-reduction) catalysts, in order to catch valuable information about the behaviour of typical NO storage materials in real application conditions. Nature, thermal stability and relative amounts of the surface species formed on a commercial catalyst upon NO and 02 adsorption in the presence and in the absence of water were analysed using a novel system consisting of a quartz infrared reactor. Operando IR plus MS measurements showed that carbonates present in the fresh catalyst are removed by replacement with barium nitrate species after the first nitration of the material. Nitrate species coordinated to different barium sites are the predominant surface species under dry and wet conditions. The difference in the species stabilities suggested that barium sites possess different basicity and, therefore, that they are able to stabilize nitrates at different temperatures. At temperatures below 523 K, nitrite species were observed. The presence of water at mild temperatures in the reactant flow makes unavailable for NO adsorption the alumina sites [181]. 

Gelatine explosives, initiated by commercial detonators, will normally fire at the low velocity of detonation initially, although this may well build up quite quickly into the high velocity. For some applications a high velocity of detonation is essential. This can be ensured by the addition of barium sulphate, or other material with density exceeding 2-8, in a fine form. Such additives have the property of ensuring rapid transition to the high velocity of detonation. This is, for example, of particular importance when the explosive is to be fired under a hydrostatic head, as in submarine work. 

Thus, by an application of the common ion effect, the solubility of barium sulfate has been reduced to produce 104-fold less free barium ion in solution, thus further reducing the risk of barium toxicity. 

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