Aluminum concentration

Substituting the sample s initial rate into the calibration equation gives an aluminum concentration of 0.331 )J,M. 

Operation and Control. Control of a chromium phosphate conversion coating bath requires monitoring chromium and aluminum concentrations, active fluoride level, and temperature. Coating weight is very sensitive to active, ie, uncomplexed, fluoride. An innovative electrochemical method using a siHcon electrode (25) is employed for measuring active fluoride. A special precaution in chromium phosphate bath operation is the... 

The effect of a second phase is demonstrated in the copper—aluminum system, where increasing aluminum concentration causes the alloy system to change to a polyphase alloy. By obtaining a fine dispersion of the phase, the yield strength is increased from 225 to 480 MPa (33,000—70,000 psi). 

If chronic use is required in patients with end-stage renal disease, monitor serum aluminum concentrations every... 

Soil-pH may influence both the concentrations of ions in the soil solution and the charge characteristics of the clay. Dispersion of clays is thus, to some extent, a pH-dependent process. At soil-pH(H2o,i i) values below 5, the aluminum concentration of the soil solution is normally sufficiently high to keep clay flocculated (Al3+ is preferentially adsorbed over divalent and monovalent ions in the soil solution). Between pH 5.5 and 7.0, the content of exchangeable aluminum is low . If concentrations of divalent ions are low, clay can disperse. At still higher pH values, divalent bases will normally keep the clay flocculated unless there is a strong dominance ofNa+-ions in the soil solution. 

Figure 2 clearly indicates a large variability in both the sites occupied by Al atoms and the concentration of the Al atoms in these sites for the ZSM-5 samples studied. Even samples with similar framework aluminum concentration exhibit very different Al sitings as well as Al concentrations in the individual occupied T sites. This fact clearly rules out that the Al siting in the zeolite framework is random or is controlled by thermodynamic stability. It rather shows that the conditions of the synthesis are responsible for the Al siting in the framework. 

Both ratio of base cations to aluminum, and the aluminum concentrations, are used as indicators for steady-state geochemical and biogeochemical processes. By assigning established critical loads to these indicators (for example, the concentrations of aluminum in soil solution should not exceed 0.2 meq/L and the base cations to aluminum ratio should not be less than 1), it is possible to compute the allowable acidification for each ecosystem. An extensive overview of critical values for the ratio of base cations to aluminum for a large variety of plants and trees can be found in Prof. Sverdrup s papers (for example, Sverdrup et al., 1995 Warfvinge et al., 1992, 1993). 

Pseudo total Aluminum concentration was the lowest in surface soils (1.13 0.15%) and reached a maximum in 37-57cm depth (1.4 0.21%). The increase in the concentration of A1 with depth upto 57cm implied a maximum accumulation in 37-57cm depth. A1 in surface layers appeared to be independent of the influences of soi physical characteristics,... 

Zeolite ZSM-5. Zeolite catalytic selectivity is usually related to channel size, but for many reactions catalytic activity and selectivity also are influenced by the number of acid sites that contact reactant molecules. Since the acidity of a local region within a zeolite crystal is directly related to the aluminum concentration in that region 14], it is important to know the... 

Abstract A preconcentration method using Amberlite XAD-16 column for the enrichment of aluminum was proposed. The optimization process was carried out using fractional factorial design. The factors involved were pH, resin amount, reagent/metal mole ratio, elution volume and samphng flow rate. The absorbance was used as analytical response. Using the optimised experimental conditions, the proposed procedure allowed determination of aluminum with a detection limit (3o/s) of 6.1 ig L and a quantification limit (lOa/s) of 20.2 pg L, and a precision which was calculated as relative standard deviation (RSD) of 2.4% for aluminum concentration of 30 pg L . The preconcentration factor of 100 was obtained. These results demonstrated that this procedure could be applied for separation and preconcentration of aluminum in the presence of several matrix. 

Analytikjena Atomic Absorption Spectrometer equipped with an aluminum hollow cathode lamp was used to measure aluminum concentrations. The wavelength and spectral bandpass were set at 309.3 and 1.2 run, respectively. Gas/Oxidant ratio was 0.553. A digital pH meter model Metrohm was used for pH measurements. 

One study suggested a possible link of aluminum in public water supplies with the occurrence of Alzheimer disease in 88 county districts of England and Wales. In districts in which the mean aluminum concentration in water exceeded O.llmg/1, rates were 1.5 times higher than in districts in which the mean levels were less than 0.01 mg/1. The results have been challenged on the basis of study design and on the interpretation of the relative significance of the dose of aluminum from water as a fraction of total dietary intake."... 

The surface silicon concentration at the first saturation was found to decrease with the silica to alumina ratio of zeolite, shown in Table 1. A relatively small concentration on silica was remarkable. Saturated silicon concentration therefore seemed to be correlated with the aluminum concentration of zeolites. 

Fia. 23. Specific radioactivity (and corresponding values of —CjHs mol. per mol. of polymerized CsHj) of the atactic polypropylene fraction, as function of the square root of the alkyl-aluminum concentration. (Tests performed with C-labeled Al(CjH()s at t = 70°, pc H, = 450 mm. Hg, grounda-TiCU sample A). 

Figure 13-10 Relation of total aluminum (including dissolved and suspended species) in 1 000 Norwegian lakes as a function of the pH of the lake water. The more acidic the water, the greater the aluminum concentration. [From G. Howells. Acid Rain and Add Waters, 2nd ed. (Hertfordshire Elis Horwood, 1995).]...

K. N. White, and J. J. Pbwell, Mucus Secretion by the Freshwater Snail Lymnaea stagnalis limits Aluminum Concentrations of the Aqueous Environment, Environ. Sci Technol 1998,32, 2591 M. Ravichandran, G. R. Aiken, M. M. Reddy, and... 

The colloidal silica dispersions are destabilized with hydrolyzed Al(III) primarily because of adsorption of polyhydroxo aluminum cations on the colloid surface which reduces the incipiently negative surface potential of Si02 colloids (adsorption coagulation). The pertinent solution variables describing the destabilization reaction are pH, total aluminum concentration Ct, and the ratio of aluminum dosage to the colloid surface concentration S. 

This approach is based on the premise that Al can be used as a tracer for bottom sediment material and that the concentration of Al in resus-pendable surface sediment is fairly uniform basinwide. Detailed profiles of size-fractionated particulate aluminum concentrations spaced closely in time over the unstratified period show vertical concentration profiles at nearly uniform levels, indicating that a pseudosteady state had been achieved. The mean areal pool of Al during this period was designated as the net resuspended pool (80-90% settles from the water column by September), and the quantity of surface sediment required to supply this pool was calculated. 

Alzheimer s disease (AD) is the most prevalent form of senile dementia. Up to two million people in North America suffer from it, and it is the fourth cause of death in the elderly. The cause and treatment of this disease are therefore extremely important. Although the role of aluminum in AD and its in vivo chemistry is not known in detail, patients with Alzheimer s disease have been shown to have elevated aluminum concentrations in certain parts of the brain. Aluminum appears to concentrate in the nucleus. Crosslinks with DNA strands have been found. Crosslink formation can be reversed by sequestering the aluminum with EDTA. 

Aluminum Concentrations Detected in Drinking Water in Various Regions of the United States... 

A large number of epidemiology and case-control studies have examined the potential association between oral aluminum exposure and Alzheimer s disease. A number of these studies have been criticized for flawed patient selection, poor comparability of exposed and control groups, poor exposure assessment, poor assessment of health outcomes, and weak statistical correlations (Nieboer et al. 1995 Schupf et al. 1989). Studies conducted by Martyn et al. (1989), McLachlan et al. (1996), and Michel et al. (1990) have found an association between oral exposure to aluminum and an increased risk of Alzheimer s disease. In a survey study conducted by Martyn et al. (1989), the incidence of Alzheimer s disease in individuals under the age of 70 was estimated from computerized tomographic (CT) records. The 1,203 subjects lived in 88 county districts within England and Wales. Data on aluminum concentrations in the municipal water over a 10-year period were obtained from water authorities and water companies. The subjects were classified as having probable Alzheimer s disease, possible Alzheimer s disease, other causes of dementia, or epilepsy. The relative risks of Alzheimer s disease were elevated in the subjects living in districts with aluminum water concentrations of >0.01 mg/L. However, the relative risk exceeded unity only in the subjects with aluminum water concentrations of >0.11 mg/L (relative risk of 1.5, 95% confidence interval of 1.1-2.2). 

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