High-purity materials

Manufacture. Lithium fluoride is manufactured by the reaction of lithium carbonate or lithium hydroxide with dilute hydrofluoric acid. If the lithium carbonate is converted to the soluble bicarbonate, insolubles can be removed by filtration and a purer lithium fluoride can be made on addition of hydrofluoric acid (12). High purity material can also be made from other soluble lithium salts such as the chloride or nitrate with hydrofluoric acid or ammonium bifluoride (13). 

Flake mica is also produced from mica schist which normally contains from 30—60% recrysta11i2ed muscovite mica along with quart2 and iron minerals. The quart2 is usually not suitable for glass sand or high purity material, however. 

Purification. The method used to recover the desired alkylphenol product from the reactor output is highly dependent on the downstream use of the product and the physical properties of the alkylphenol. The downstream uses vary enormously some require no refining of the alkylphenol feedstock others require very high purity materials. Physical property differences affect both the basic type of process used for recovery and the operating conditions used within that process. 

D. I. Ryabchikov, L. L. Na2arenko, and I. P. Alimarin, eBs., Analysis of High Purity Materials, Israel Program for Scientific Information, Jemsalem, 1968. 

The properties of siHcon carbide (4—6) depend on purity, polytype, and method of formation. The measurements made on commercial, polycrystalline products should not be interpreted as being representative of single-crystal siHcon carbide. The pressureless-sintered siHcon carbides, being essentially single-phase, fine-grained, and polycrystalline, have properties distinct from both single crystals and direct-bonded siHcon carbide refractories. Table 1 Hsts the properties of the hiUy compacted, high purity material. 

Kinetic Resolutions. From a practical standpoint the principal difference between formation of a chiral molecule by kinetic resolution of a racemate and formation by asymmetric synthesis is that in the former case the maximum theoretical yield of the chiral product is 50% based on a racemic starting material. In the latter case a maximum yield of 100% is possible. If the reactivity of two enantiomers is substantially different the reaction virtually stops at 50% conversion, and enantiomericaHy pure substrate and product may be obtained ia close to 50% yield. Convenientiy, the enantiomeric purity of the substrate and the product depends strongly on the degree of conversion so that even ia those instances where reactivity of enantiomers is not substantially different, a high purity material may be obtained by sacrificing the overall yield. 

Institute of Microelectronics Technology and High Purity Materials, RAS, 142432 Chernogolovka, Russia, e-mail grazhule ipmt-hpm. ac. ru... 

Dibenzofuran [132-64-9] M 168.2, m 82.4 . Dissolved in diethyl ether, then shaken with two portions of aqueous NaOH (2M), washed with water, separated and dried (MgS04). After evaporating the ether, dibenzofuran was crystd from aq 80% EtOH and dried under vacuum. [Cass et al. J Chem Soc 1406 7958.] High purity material was obtained by zone refining. 

With increasing purity of aluminium, greater resistance to corrosion is developed. On high-purity materials, however, any pits which develop are likely to be deeper though fewer in number than those formed in more impure metal. In some special applications, notably in contact with ammonia solutions or pure water at elevated temperatures and pressures, the iron and silicon present in commercial-purity metal are beneficial and retard corrosion. Up to about 5% magnesium improves the corrosion resistance to sea-water. 

Abstract book of VIII Russian conference on optical methods of heating and high purity materials analysis, Gorikiy, 1988, p. 252. 

Obviously, direct SS-GF-ZAAS fulfils these criteria. A carefully performed homogeneity study using SS-GF-ZAAS was reported for the VDA CRMs (Cd in polyethylene) [137,223,224]. Solid sampling also allows analysis of high-purity materials (blank-free, low limits of analysis). 

Applications ICP-MS has become the technique of choice for the determination of elements in a wide range of liquid samples at concentrations in the ng L 1 to [igL-1 range. Typical applications of ICP-MS are multi-element analysis of liquids (even with high solid contents) element speciation by hyphenation to chromatographic techniques continuous on-line gas analysis multi-element trace analysis of polymers and trace analysis in high-purity materials. ICP-MS is routinely used for quality control purposes. 

ULTRA TRACE ANALYSIS High-purity materials for microelectronics... 

Cyclative cleavage strategies release the final compound into solution following intramolecular attack of a nucleophile or electrophile upon the linkage site. Synthesis byproducts and intermediates do not incorporate the necessary nucleophile or electrophile therefore only the desired products are released into solution to yield high purity materials. Seminal examples of this approach are the library syntheses of benzodiazepines and hydantoins (Scheme 3). 

Analysis of High-Purity Materials. Int. J. Mass Spectrom. 2003, 228, 127-150. 

Process inputs Ranges from crude feed stocks with variable properties to high purity materials Pure, high quality raw materials... 

The most common material of construction is PFA Teflon . This high-purity material has become the material of choice due to its universal chemical resistance, nonstick surface properties, availability and compatibility of parts, and general historical and emotional acceptance. Other materials, such as polyethylene and polypropylene, are becoming more widely... 

The molten material attacks quartz. Therefore, quartz boats coated with carbon by pyrolytic decomposition of methane should be used in refining the compound to obtain high purity material. 

Three alternative methods may be mentioned here, which give high purity material and are less tedious than the one described above. These are (1) ion exchange, (2) metallothermic reduction, and (3) electrolysis. 

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