Chelation organic acids

Using these agents, especially the particularly effective 1 2 complex 4 with salicylic acid, metallization can be carried out easily at high pH without precipitation of inert chromium hydroxide. In certain cases a 1 1 chromium complex that still contains chelating organic acid as ligand can also be obtained. 

A range of other systems of Ga + with chelating organic acids has been studied and solution equilibria data have been obtained. Based on these investigations it is clear that in aU cases basic complexes (i.e. those containing oxo or hydroxo ligands) are involved, and the hydrated hydroxide cation [Ga(OH)] + shows greater reactivity compared with the hydrated ion of Ga +. 

Fang, T.J. and Tsai, H.C. 2003. Growth patterns of Escherichia coli 0157 H7 in ground beef treated with nisin, chelators, organic acids and their combinations immobilized in calcium alginate gels. Food Microbiology 20 243-253. 

CCA has decades of proven performanee in field trials and in-service. With the correct species and treatment CCA provided an assured in-ground service life in excess of 50 years. Reeently Bull (2001) has proposed that the fixation produets of CCA are dominated by ehromium (III) arsenate, chromium (III) hydroxide and wood-carboxylate-eopper (II) eomplexes. CCA is potent precisely because it is bioavailable - and persistent. Signifieantly the separation of copper from chromium and arsenic is consistent with the observation that acetie aeid and chelating organic acids - and silage or eompost - under eertain eireumstanees ean promote leaching and early failure (Cooper and Ung, 1995 Kazi and Cooper, 1998). 

The presence of chelating organic acids or sugars prevents the precipitation of Co " by alkalis. 

In common with other hydroxy organic acids, tartaric acid complexes many metal ions. Formation constants for tartaric acid chelates with various metal ions are as follows Ca, 2.9 Cu, 3.2 Mg, 1.4 and Zn, 2.7 (68). In aqueous solution, tartaric acid can be mildly corrosive toward carbon steels, but under normal conditions it is noncorrosive to stainless steels (Table 9) (27). 

Nickel Salts and Chelates. Nickel salts of simple organic acids can be prepared by reaction of the organic acid and nickel carbonate of nickel hydroxide reaction of the acid and a water solution of a simple nickel salt and, in some cases, reaction of the acid and fine nickel powder or black nickel oxide. 

Tetraalkyl titanates react with organic borates, B(OR )2, to give complexes of the general formula Ti(OR)4 B(OR )2, which are useful as catalysts and cross-linking agents (562). Mixtures of chelated organic titanates such as TYZOR TE and TYZOR LA with alkaU metal borates, such as borax, or boric acid can be used to produce shear-stable fracturing fluids (563). 

Chelation, using ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), diethylenetri-aminepentacetic acid (DTPA), phosphonates, and other compounds, together with organic acids such as citric or formic acid. Here, the reaction is ... 

Either particulate sol or polymeric sol has been used for thin film coatings. The polymeric sol was fabricated by partial hydrolysis of corresponding metal alkoxide. If the rate of hydrolysis or condensation is very fast, then some kinds of organic acids, beta-dicarbonyls, and alkanolamines have been used as chelating agent in sol-gel processes to control the extent and direction of the hydrolysis-condensation reaction by forming a strong complex with alkoxide. [2]. 

In addition to phenolic substances, there are other components present in foods which have no antioxidant activity of their own, but which increase that of phenolic antioxidants. They are called synergists, and they should be accounted for in any discussion of antioxidant activity. Polyvalent organic acids, amino acids, phospholipids (lecithin) and various chelating agents belong to this group. Proteins may modify the efficiency of antioxidants as they react with the reaction products of both antioxidants and synergists. 

Boron zirconimn chelates from ammonium hydroxide water-soluble amines sodium or potassimn zirconium and organic acid salts such as lactates, citrates, tartrates, glycolates, malates, gluconates, glycerates, and mandelates with polyols such as glycerol, erythritol, arabitol, xylitol, sorbitol, dulcitol, mannitol, inositol, monosaccharides, and disaccharides [463,464,1592,1593]... 

In the first case the mechanisms are based on an increased reducing capacity of Fe(lll)-chelates, a necessary step in the uptake process, with a concurrent increase in acidification and release of organic acids into the rhizosphere in the latter case molecules having high affinity for Fe (phytosiderophores) are synthesized and released into the rhizosphere when Fe is lacking. 

In the rhizosphere, microorganisms utilize either organic acids or phytosiderophores to transport iron or produce their own low-molecular-weight metal chelators, called siderophores. There are a wide variety of siderophores in nature and some of them have now been identified and chemically purified (54). Pre.sently, three general mechanisms are recognized for utilization of these compounds by microorganisms. These include a shuttle mechanism in which chelators deliver iron to a reductase on the cell surface, direct uptake of metallated siderophores with destructive hydrolysis of the chelator inside the cell, and direct uptake followed by reductive removal of iron and resecretion of the chelator (for reviews, see Refs. 29 and 54). 

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