Chelating material

The formulation of calcium chelate materials is based upon the formation of a low-solubiUty chelate between calcium hydroxide and a sahcylate. Dycal utilizes the reaction product of a polyhydric compound and sahcyhc acid. Other sahcyhc acid esters can be similarly used. Vehicles used to carry the calcium hydroxide, extenders, and fillers may include mineral oil, A/-ethyl- -toluenesulfonamide [80-39-7] and polymeric fluids. The filler additions may include titanium dioxide [13463-67-7] zinc oxide, sihca [7631-86-9], calcium sulfate, and barium sulfate [7727-43-7]. Zinc oxide and barium sulfate are useflil as x-ray opacifying agents to ensure a density greater than that of normal tooth stmcture. Resins, rosin, limed rosins, and modified rosins may serve as modifiers of the physical characteristics in both the unset and set states. 

Tanaka et al. reported a series of oxadiazole metal chelate materials (97 99) (Scheme 3.31). However, these complexes suffer stability issues due to the intrinsic instability of the excited state of the molecules. Therefore the lifetimes of OLEDs fabricated using these compounds are fairly short [153,154]. 

Other metal chelate materials of ligands such as benzimidazole have been disclosed in a Kodak patent as their beryllium or aluminum complexes (244) [271]. These materials generate very pure blue color within CIE range of (0.15-0.16, 0.12-0.17) [154,272]. 

Hellmuth believes that the polymeric material forms. If magnesium acetate is simply the internally chelated material, then it should be quickly washed away. The combination of calcium and magnesium acetates is known as CMA. CMA is more expensive than sodium chloride or calcium chloride, but it does not damage plant life and it has a much longer effective life. The polymer seeks the cracks and crevices in and around the pavement and remains until needed again to lower the freezing point of water. Often, one application of CMA is sufficient for a winter season. 

Soil Organic matter as a natural chelating material. Compost Sci. 4, 25-28 (1964). 

Element- and group-specific separations have been achieved for multi-element analyses with chelating materials (, ) Using this approach chemical separations can be tailored for certain... 

A solid chelating material, l-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of separating traces of Co(II) from natural waters [19]. Open-cell polyurethane foam loaded with PAN azo reagent [20], and organic resins modified with nitroso-R salt have been used similarly [21,22]. 

In the early stages of decomposition of plant and animal substances many simple substances are formed that can readily react as chelating materials. Many, or most, of the reaction products would be water soluble but probably rather transitory since they would be subject to further biological attack. 

Chelate materials of this type are products of reaction of a metal base, such as calcium hydroxide or metal oxide, with weakly acidic organic substances with at least two functional groups. The ones used clinically are typically hydrolytically unstable, and this is responsible for their therapeutic effects. Ions released have beneficial properties, reducing inflanunation, being bacteriostatic and stimulating the odontoblasts to form secondary dentine. Ideally, calcium hydroxide chelates of this kind dissolve completely with time, and thus have the maximum possible therapeutic effect. 

One final example of a separation by a chelation interaction is that of aliphatic diolacetonides. The chelating material had the following basic structure ... 

Chelated materials were formed from reaction of vanadocene dichloride with heterocyclic 1,2-dithiolates [26], The product from l,3-dithiolene-2-thione-4,5-ditholate is given in (2). 

Correction of these micronutrient deficiencies may be accomplished by soil or foliar application. Boron, copper, zinc, manganese, and molybdenum are usually applied to the soil. Molybdenum. is required..in such sraall quantities that it is often dusted on seeds. Iron is usually added as a chelated material and is foliar applied. 

The rate of autoxidation is thus proportional to the square root of the metal ion concentration. However, this rate does not hold when the concentration of metal initiator is too small to measure. In many food and biological systems, metal catalysts may be coordinated with ligands as complexes or may exist as dimers or higher molecular weight compounds. Other chelating materials may form strong complexes with metals and inactivate their catalytic effects in promoting hydroperoxide decomposition (Chapter 4). 

The wear and corrosion of pulp mill equipment (including chipper knives) is due not only to mechanical abrasion, but also to the acidity of the wood and to the chelating materials in the secondary components. 

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