Aluminium occurrence

Evaluating the distribution diagram of different forms of the aluminium occurrence, at pH < 4 simple hydrated Al cation predominates in the solution, and at pH > 7 anionic hydroxo complexes prevail. The lowest solubility of hydrated aluminium oxide is achieved at about pH 5.5. Solubility rapidly increases in the alkaline region. Low concentrations of soluble aluminium can be maintained within a rather narrow pH scale. Precipitation of aluminium salts appears at pH < 4 and at the initial A1 concentration below 0.01 mol 1 . ... 

Akimov was one of the earliest investigators to report that the pitting of aluminium and aluminium alloys in sea-water could be prevented by coupling to zinc. He also drew attention to the occurrence of a tenacious... 

In the case of alloys having one constituent considerably more reactive to oxygen than the others, conditions of temperature, pressure and atmosphere may be selected in which the reactive element is preferentially oxidised. Price and Thomas used this technique to develop films of the oxides of beryllium, aluminium, etc. on silver-base alloys, and thereby to confer improved tarnish resistance on these alloys. If conditions are so selected that the inward diffusion of oxygen is faster than outward diffusion of the reactive element, the oxide will be formed as small dispersed particles beneath the surface of the alloy. The phenomenon is known as internal oxidation and is of quite common occurrence, usually in association with a continuous surface layer of oxides of the major constituents of the alloy. 

Although commonly formed from endogenous material, the occurrence of synovial crystals formed following environmental exposure to exogenous agents is indicated by the identification of both aluminium phosphate and aluminium silicate particulates (Netter etal., 1983, 1991). It is noteworthy in this context that arthritic symptoms have been reported following the... 

Occurrence. It is the commonest metallic element in the earth s crust. Aluminium occurs in many silicates such as micas and feldspars, hydroxo oxide (bauxite), cryolite (Na3AlF6). 

Occurrence. Gallium ores are rare. It occurs in aluminium and zinc ores, for instance bauxite and zinc blende. 

Polynuclear aromatic hydrocarbons (PAH), of widespread occurrence in the environment, result from incomplete combustion of carbon- and hydrogen-containing substances. Many PAHs are well-recognized carcinogens and mutagens. Several industrial processes, such as fossil fuel conversion and production of aluminium and ferroalloys, can produce PAHs and result in their occurence in the working environment. 

Solid-state growth of the AlSb layer between aluminium and antimony is due to the occurrence of the following partial chemical reactions ( see Fig. 1.13) ... 

Occurrence.—Many silicates contain traces of lithium, usually associated with large proportions of sodium and potassium. Lithium compounds are mainly derived from lepidolite or lithia-mica, a double fluosilicate of aluminium and an alkali-metal, containing 0 8—2-7 per cent, of lithium and petalite, a double silicate of aluminium and lithium with an admixture of sodium, containing 2 per cent, of lithium. 

Occurrence.—The principal mineral containing caesium is pollucite, a double silicate with aluminium having the approximate composition Cs4AI4H2Si9027, found in Maine and in Elba.1 It accompanies the other alkali-metals, being found in traces in the Stassfurt salt deposits and in many mineral springs. 

We are all exposed to aluminium from the metal utensils we use and also from the occasional use of medicinal preparations such as antacids, but it is poorly absorbed and the risk is probably very small. Dialysis patients with renal disease were found to be at risk of brain damage due to the aluminium derived from the equipment. Realization of this led to a lowering of the exposure of such patients, which decreased the occurrence of toxic effects of aluminium. Patients on dialysis with end stage renal disease, in whom some accumulation of aluminium occurred, showed evidence of metabolic abnormalities and in psychomotor function. 

Apart from simple corrosive attack on a metal surface, Gabel reported a more specific situation leading to corrosion. This occurred when a dry-film-lubricated metal surface was in contact with an unlubricated anodized aluminium surface. Laboratory investigation at 95% relative humidity and 49°C (120°F) confirmed that in this situation the corrosion resistance of the anodized aluminium was reduced from 1100 hours to fewer than 200 hours. It was not clear whether dissimilar metals were involved, but the occurrence suggested that corrosion might be due to the development of an external potential in the presence of an electrolyte. 

Amorphous silica-alumina (Si02-AI2O3) has been also tested for the catalytic cracking of polyolefins [36, 37, 43]. This acid solid is featured by having a broad distribution of pore sizes, which is determined by the synthesis procedure. Moreover, the occurrence of a bimodal pore size distribntion (e.g. meso-macroporous) is usually present. The aluminium... 

Encephalopathy due to high serum aluminium concentrations has been reported in acute renal insufficiency (SEDA-17, 273) (72). Unsuspected intake of citrate from other sources has apparently promoted the occurrence of aluminium encephalopathy in renal insufficiency (73). Most reported instances of encephalopathy after alum irrigation have occurred in patients with compromised renal function. 

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