Wet chemical means

Citrate-capped y-Fe203 nanocrystals were prepared by wet-chemical means, by modifying the procedure of Ngo and Pileni.11 The preparation yields a sol, which can be precipi-... 

Figure 6. Secondary electron image of a defect particle before (left) and after (right) removal of passivation and metallization by wet chemical means.

Transformed rare earth and actinide intermetallic compounds are shown to be very active as catalysts for the synthesis of hydrocarbons from CO2 and hydrogen. Transformed LaNis and ThNis the most active of the materials studied they have a turnover number for CH formation of 2.7 and 4.7 X 10 sec at 205°C, respectively, compared with I X 10 sec for commercial silica-supported nickel catalysts. Nickel intermetallics and CeFe2 show high selectivity for CHj formation. ThFcs shows substantial formation of C2H6 (15%) as well as CHi,. The catalysts are transformed extensively during the experiment into transition metal supported on rare earth or actinide oxide. Those mixtures are much more active than supported catalysts formed by conventional wet chemical means. 

In order to determine TOC/DOC, the organic substances contained in the water sample are oxidized with UV rays or by wet-chemical means, or burnt... 

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

Detergency may be defined as the removal of dirt from solid surfaces by surface chemical means [29], and may be related to several surfactant properties, including wetting and rewelting ability, foam generation, and surface and interfacial tension. It has long been observed... 

The micro channels were made by isotropic wet chemical etching of metal plates. The plates were tightened by various means they were either glued, stacked to-... 

Using a newly developed, transversely heated graphite atomizer and D2-back-ground correction (for details see Sections 2.2 and 4.3), Cd, Pb and Cr were determined in cement and river sediment samples. Of the various calibration approaches applied the best results, also in comparison with wet chemical procedures, were achieved with calibration curves constructed by means of different BCR CRMs with different analyte concentrations and usually n = to individual intakes (Nowka and Muller 1997). 

Wet chemical analysis usually involves chemical reactions or classical reaction stoichiometry, but no electronic instrumentation beyond a weighing device. Wet chemical analysis techniques are classical techniques, meaning they have been in use in the analytical laboratory for many years, before electronic devices came on the scene. If executed properly, they have a high degree of inherent accuracy and precision, but they take more time to execute. 

Natural ceramic raw materials have the disadvantage that they are not soluble in water and consequently unsuitable for wet chemical analysis. That is why they are first destructed in the laboratory. Destruction means that a substance or a mixture of substances is heated together with a substance or a mixture of substances and as a result the component to be destructed is largely separated into ions and consequently dissolves in water. The destruction method and the substances are specific for the substance undergoing the destruction. Different methods applied to the same substance lead to different results. 

A complete analysis characterizing greater than 95 percent of a biomass sample can require up to 30 independent measurements to report the concentration of 10 to 15 constituents. Table 33.1 shows the confidence intervals for the standard wet chemical methods used to characterize biomass feedstocks. The confidence interval of 1.5 percent for glucan means that when a value of 38 percent is reported for a biomass sample, there is a 98 percent probability that the true glucan concentration lies between 36.5 and 39.5 percent. Many of these values were determined... 

Atomic absorption methods combine the specificity of other atomic spectral methods with the adaptability of wet chemical methods. High specificity means that elements can be determined in the presence of each other. Separations, which are necessary with almost all other forms of wet analysis, are reduced to a minimum and often avoided altogether, making a typical atomic absorption analytical procedure attractively simple. This fact, combined with the ease of handling a modern atomic absorption spectrometer, makes it possible for routine analyses to be carried out quickly and economically by relatively junior laboratory staff. 

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