Aluminum concentrations, variation

The aluminum concentration also influenced on the electrical properties, as shown in Figure 5, mainly in the breakdown electric field variation that had been related to decreasing of grain size. The samples showed nonlinear coefficient (a) of similar values, but the sample prepared by Pechini method and with 0.2% AI2O3 had the highest value for a (21.7) and the breakdown electric field (due to the smaller grain size). 

Fluoride. A fluoride concentration of ca 1 mg/L is helpful in preventing dental caries. Eluoride is deterrnined potentiometrically with an ion-selective electrode. A buffer solution of high total ionic strength is added to the solution to eliminate variations in sample ionic strength and to maintain the sample at pH 5—8, the optimum range for measurement. (Cyclohexylenedinitrilo)tetraacetic acid (CDTA) is usually added to the buffer solution to complex aluminum and thereby prevent its interference. If fluoroborate ion is present, the sample should be distilled from a concentrated sulfuric acid solution to hydrolyze the fluoroborate to free fluoride prior to the electrode measurement (26,27). 

Certain varieties of hydrangeas are extremely popular for their ability to vary in color from blue to pink with growing conditions (see color Fig. 9.4.1). Research has determined that the actual mechanism for color variation is determined by the concentration of aluminum compounds in the flowersJ J In the presence of aluminum, blue flowers result in the absence of aluminum compounds, pink flowers predominate. 

In the other study. X-ray fluorescence spectroscopy was used to analyze trace element concentrations by observing dusts on 37 ram diameter cellulose acetate filters (20). Twenty-three elutriator and twenty-three area samples from 10 different bales of cotton were analyzed. The average fraction of total dust accounted for by the elements analyzed was 14.4% amd 7.6% for vertical elutriator and area samples, respectively. Although the variation in absolute quantity of atn element was high, the relative abundance of an element was consistent for measurements within a bale. Averaged over all the samples analyzed, calcium was the most abundant element detected (3.6%), followed by silicon (2.9%), potassium (2.7%), iron (1.1%), aluminum (1.1%), sulfur (1.0%), chlorine (0.8%) and phosphorous (0.6%). Other elements detected in smaller aunounts included titanium, manganese, nickel, copper, zinc, bromine, rubidium, strontium, barium, mercury amd lead. 

The presence of high levels of suspended solids in stream surface water during storm episodes resulted in higher concentrations of adsorbed aluminum than in the absence of suspended solids (Goenaga and Williams 1988). The increased adsorption was not strictly linear, with higher concentrations of suspended solids due to variations in the particle size distribution and the nature of the particles. 

The concentration levels of TriCDTs, TeCDTs, and PeCDTs in emissions and waste from an aluminum smelter and a car shredder have been found to be comparable to those of PCDDs and PCDFs. The number of individual TeCDT isomers was larger than the number of TeCDD isomers. PCDTs were effectively removed by the baghouse filter, more effectively than the PCDDs. Different TeCDT isomers had different adsorption tendencies on the filter system. Probably some samples from the car shredder contained some TriCTAs and possibly also some TeCTAs in low concentrations. A very large temporal variation can exist in the concentrations of organochlorine compounds in the emissions from car shredder plants because the raw material used is not very homogeneous [14]. 

The two elements calcium and aluminum are RLEs. The assumption is usually made that aU RLEs are present in the primitive mantle of the Earth in chondritic proportions. Chondritic (undifferentiated) meteorites show significant variations in the absolute abundances of refractory elements but have, with few exceptions discussed below, the same relative abundances of lithophile and siderophile refractory elements. By analogy, the Earth s mantle abundances of refractory lithophile elements are assumed to occur in chondritic relative proportions in the primitive mantle, which is thus characterized by a single RLE/Mg ratio. This ratio is often normalized to the Cl-chondrite ratio and the resulting ratio, written as (RLE/Mg)N, is a measure of the concentration level of the refractory component in the Earth. A single factor of (RLE/Mg) valid for all RLEs is a basic assumption in this procedure and will be calculated from mass balance considerations. 

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