Aluminium effect

Zr-Cp interaction presumably by y-aluminium effect. hZr-Cl, and Zr-S[, contacts, respectively. 

Van Praag, H.J. and F. Weissen (1985). Aluminium effects on spruce and beech... 

Qafoku, N.P., Ainsworth, C.C., Szecsody, J.E., Qafoku, O.S. Aluminium effect on dissolution and precipitation under hyper alkaline conditions. J. Environ. Qual. 32(6), 2354-2363 (2003)... 

Scott, A. D., J. L. Ahlrichs, and G. Stanford, 1957. Aluminium effect on potassium fixation by Wyoming bentonite. Soil Sci. 84 377. 

The data in Tables 4.2 and 4.3 refer to ions in aqueous acid solution for cations, this means effectively [MlHjO), ]" species. However, we have already seen that the hydrated cations of elements such as aluminium or iron undergo hydrolysis when the pH is increased (p. 46). We may then assume (correctly), that the redox potential of the system... 

Aqueous ammonia can also behave as a weak base giving hydroxide ions in solution. However, addition of aqueous ammonia to a solution of a cation which normally forms an insoluble hydroxide may not always precipitate the latter, because (a) the ammonia may form a complex ammine with the cation and (b) because the concentration of hydroxide ions available in aqueous ammonia may be insufficient to exceed the solubility product of the cation hydroxide. Effects (a) and (b) may operate simultaneously. The hydroxyl ion concentration of aqueous ammonia can be further reduced by the addition of ammonium chloride hence this mixture can be used to precipitate the hydroxides of, for example, aluminium and chrom-ium(III) but not nickel(II) or cobalt(II). 

The stock solution of quinoline-sulphur poison is prepared by refluxing I g. of sulphur with 6 g. of quinoline for 5 hours and diluting the resulting brown liquid to 70 nJ. with xylene which has been purified by distilling over anhydrous aluminium chloride. The addition of the quinoline - sulphur poison ensures that the reduction does not proceed beyond the aldehyde stage it merely slows up the reaction and has no harmful effects. 

Acetone in conjunction with benzene as a solvent is widely employed. With cyclohexanone as the hydrogen acceptor, coupled with toluene or xylene as solvent, the use of higher reaction temperatures is possible and consequently the reaction time is considerably reduced furthermore, the excess of cyclohexanone can be easily separated from the reaction product by steam distillation. At least 0 25 mol of alkoxide per mol of alcohol is used however, since an excess of alkoxide has no detrimental effect 1 to 3 mols of aluminium alkoxide is recommended, particularly as water, either present in the reagents or formed during secondary reactions, will remove an equivalent quantity of the reagent. In the oxidation of steroids 50-200 mols of acetone or 10-20 mols of cyclohexanone are generally employed. 

The effect of ligands on the endo-exo selectivity of Lewis-acid catalysed Diels-Alder reactions has received little attention. Interestingly, Yamamoto et al." reported an aluminium catalyst that produces mainly exo Diels-Alder adduct. The endo-approach of the diene, which is normally preferred, is blocked by a bulky group in the ligand. 

Copper, aluminium, steel and galvanized iron are the most widely used metals for the purpose of grounding. Choice of any of them will depend upon availability and economics in addition to the climatic conditions (corrosion effect) at the site of installation. In Table 22.3 we provide a brief comparison of these metals for the most appropriate choice of the metal for the required application. 

The phenomenon uneven distribution of current within the same conductor due to the inductive effect is known as the skin effect and results in an increased effective resistance of the conductor. The ratio of a.c. to d.c. resistance, R JR. is the measure of the skin effect and is known as the skin effect ratio . Figure 28.13(a) illustrates the skin elTect for various types and sizes of aluminium in flat sections. For easy reference, the skin effects in isolated round (solid or hollow) and channel conductors (in box form) are also shown in Figures 28.13(b) and (c) respectively. 

Figure 28.13(a) Skin effect in isolated rectangular busbars, (neglecting the proximity effect) (Courtesy l ndian Aluminium Co, based Alcon of Canada)... 

Skin effect ratio RaolRao horn the graph of Figure 28.13(a), at an operating temperature of 85°C for a cross-sectional area of 25.8 cm (4 x 101.6x0.635) for an ElE-fVl grade of aluminium having... 

For this area of cross-section, the skin effect ratio Ffac Hic from Figure 28.13(a) for aluminium grade E-91E at 85°C, having b/a = 152.4/44.45 - 3.43 measures almost 1.425 by approximating the interpolation,... 

X (p in Q cm) as in Table 30.1 /= frequency of the system in Hz p = effective permeability of the medium in which the field exists (aluminium in the present case), and will depend upon the electric field induced in the enclosure... 

Introduction Types of metal-enclosed bus systems Design parameters and service conditions for a metal enclosed bus system Short-circuit effects Service conditions Other design considerations Skin effect Proximity effect Sample calculation for designing a 2500 A non-isolaled phase aluminium busbar systern... 

The important thing about the oxide film is that it acts as a barrier which keeps the oxygen and iron atoms apart and cuts down the rate at which these atoms react to form more iron oxide. Aluminium, and most other materials, form oxide barrier layers in just the same sort of way - but the oxide layer on aluminium is a much more effective barrier than the oxide film on iron is. 

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