Activity of decomposed

In their now classic text on decomposition in terrestrial ecosystem, Swift et al. (1979) outlined three broad groups of factors that govern decomposition of organic residues in soils. The three groups of factors are the resource (or substrate) quality of the organic residue, the environmental factors, and the presence and activity of decomposer organisms. 

Ozaki, A. Kitano, M. Itoh, N. Knroda, K. Furusawa, N. Masnda, T. Yamagnchi, H. Mntagenicity and DNA-damaging activity of decomposed products of food colors under UV irradiation. Food Chem. Toxicol. 1998, 36, 811-817. 

Scopolamine (42), an optically active, viscous Hquid, also isolated from Solanaceae, eg. Datura metell. decomposes on standing and is thus usually both used and stored as its hydrobromide salt. The salt is employed as a sedative or, less commonly, as a prophylactic for motion sickness. It also has some history of use ia conjunction with narcotics as it appears to enhance their analgesic effects. BiogeneticaHy, scopolamine is clearly an oxidation product of atropiae, or, more precisely, because it is optically active, of (—)-hyoscyamiae. 

Decomposition of Zircon. Zircon sand is inert and refractory. Therefore the first extractive step is to convert the zirconium and hafnium portions into active forms amenable to the subsequent processing scheme. For the production of hafnium, this is done in the United States by carbochlorination as shown in Figure 1. In the Ukraine, fluorosiUcate fusion is used. Caustic fusion is the usual starting procedure for the production of aqueous zirconium chemicals, which usually does not involve hafnium separation. Other methods of decomposing zircon such as plasma dissociation or lime fusions are used for production of some grades of zirconium oxide. 

Anionic Polymerization of Cyclic Siloxanes. The anionic polymerization of cyclosiloxanes can be performed in the presence of a wide variety of strong bases such as hydroxides, alcoholates, or silanolates of alkaH metals (59,68). Commercially, the most important catalyst is potassium silanolate. The activity of the alkaH metal hydroxides increases in the foUowing sequence LiOH < NaOH < KOH < CsOH, which is also the order in which the degree of ionization of thein hydroxides increases (90). Another important class of catalysts is tetraalkyl ammonium, phosphonium hydroxides, and silanolates (91—93). These catalysts undergo thermal degradation when the polymer is heated above the temperature requited (typically >150°C) to decompose the catalyst, giving volatile products and the neutral, thermally stable polymer. 

A small fraction of the hydrocarbons decompose and deposit on the catalyst as carbon. Although the effect is minute ia terms of yield losses, this carbon can stiU significantly reduce the activity of the catalyst. The carbon is formed from cracking of alkyl groups on the aromatic ring and of nonaromatics present ia certain ethylbenzene feedstocks. It can be removed by the water gas reaction, which is catalyzed by potassium compounds ia the catalyst. Steam, which is... 

Metal-Catalyzed Oxidation. Trace quantities of transition metal ions catalyze the decomposition of hydroperoxides to radical species and greatiy accelerate the rate of oxidation. Most effective are those metal ions that undergo one-electron transfer reactions, eg, copper, iron, cobalt, and manganese ions (9). The metal catalyst is an active hydroperoxide decomposer in both its higher and its lower oxidation states. In the overall reaction, two molecules of hydroperoxide decompose to peroxy and alkoxy radicals (eq. 5). 

Divalent Sulfur Derivatives. A diaLkyl ester of thiodipropionic acid (16) is capable of decomposing at least 20 moles of hydroperoxide (17). Some of the reactions contributing to the antioxidant activity of these compounds are shown in Figure 3. 

Monochlorophenols. Chlorination of phenol [108-95-2] between 50 and 120°C gives a ortho ratio of 1.65. To improve the selectivity in the paia position, it is possible to use dialkyl sulfides, diaiyl sulfides (12), oi alkyl and aiyl sulfides combined. Sulfides are active only at low tempeiatuies (<50 C), because at high tempeiatuies the active species decomposes into sulfui and chlorine. 

Poly(L-malate) decomposes spontaneously to L-ma-late by ester hydrolysis [2,4,5]. Hydrolytic degradation of the polymer sodium salt at pH 7.0 and 37°C results in a random cleavage of the polymer, the molecular mass decreasing by 50% after a period of 10 h [2]. The rate of hydrolysis is accelerated in acidic and alkaline solutions. This was first noted by changes in the activity of the polymer to inhibit DNA polymerase a of P. polycephalum [4]. The explanation of this phenomenon was that the degradation was slowest between pH 5-9 (Fig. 2) as would be expected if it were acid/base-catalyzed. In choosing a buffer, one should be aware of specific buffer catalysis. We found that the polymer was more stable in phosphate buffer than in Tris/HCl-buffer. 

Sulphuric acid is used to a very large extent for pickling low-alloy steels. The rate at which it removes the scale depends on (q) the porosity and number of cracks in the scale, (b) the relative amounts of wiistite, decomposed wiistite, magnetite and haematite in the scale, and (c) factors affecting the activity of the pickle. 

Ag2COa can be prepared in two forms described [757] as active , readily decomposed at 439 K, and inactive , which achieved the same rate of decomposition only at 593 K. Reaction yielded Ag20 and C02 or, at higher temperature (> 520 K) Ag, 02 and C02. 

Wydeven [865] concludes that, in the presence of Co304 (6.8%), up to 60% of the reactant NaC103 decomposed in the solid state. During subsequent melting, there was an increase in reaction rate. The catalytic activity of the additive was ascribed to the electron accepting properties of the oxide (Co304 is a p-type semi-conductor). The apparent value of E increased from 120 to 200 kJ mole 1 between a = 0.05 and 0.5. 

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