Alkali elements

CaC03 plus NH3CI Ni For decomposing silicates in the determination of alkali element... 

In Chapter 5 we identified metals by their high electrical conductivity. Now we can explain why they conduct electric current so well. It is because there are some electrons present in the crystal lattice that are extremely mobile. These conduction electrons move throughout the metallic crystal without specific attachment to particular atoms. The alkali elements form metals because of the ease of freeing one electron per atom to provide a reservoir of conduction electrons. The ease of freeing these conduction electrons derives from the stability of the residual, inert gas-like atoms. 

Again, we see that the alkali metals display likeness in their reactions with water. Furthermore, the reaction products always include an aqueous ion of the alkali element in which one electron has been removed, giving a 1+ ion. 

An alkali element produces ions having the same electron population as atoms of the preceding inert gas. In what ways do these ions differ from the inert gases In what ways are they alike ... 

As in the case of K" ", if the eoncentration of alkali elements (Cs" ", Rb, Li ) are controlled by feldspars, it is convenient to take into aecount of the following exchange reaction,... 

The concentrations of Rb and Cs in feldspars in geothermal areas have not been studied. However, if the concentration ranges are similar to those observed for feldspars in common igneous rocks, we can construct curves to show the relationship of the concentration of an alkali element X+ and the Cl concentration of geothermal waters (Fig. 2.4 and Fig. 2.5). It is assumed that the concentrations of Cs and Rb in feldspars range from lO -" to 10 wt% and I0 to 10 wt%, respectively. 

The high-temperature stability of SiC-based ceramics is well-known, and therefore its composite materials have been investigated for application to high-tem-perature structural materials [19-21]. However, well-known SiC-based fibers and matrix-materials stained with alkali salt are easily oxidized at high temperatures in air [22]. This would be a serious problem when these materials are used near the ocean or in a combustion gas containing alkali elements. In particular, a silicon carbide fiber containing boron (a well-known sintering aid for SiC) over 1 wt% was extensively oxidized under the above condition. In this... 

The immobilization of dissolved chemical species by adsorption and ion exchange onto mineral surfaces is an important process affecting both natural and environmentally perturbed geochemical systems. However, sorption of even chemically simple alkali elements such as Cs and Sr onto common rocks often does not achieve equilibrium nor is experimentally reversible (l). Penetration or diffusion of sorbed species into the underlying matrix has been proposed as a concurrent non-equilibration process (2). However, matrix or solid state diffusion is most often considered extremely slow at ambient temperature based on extrapolated data from high tem-... 

Mass fluxes of alkali elements transported across the solid-solution interfaces were calculated from measured decreases in solution and from known surface areas and mineral-to-solution weight-to-volume ratios. Relative rates of Cs uptake by feldspar and obsidian in the batch experiments are illustrated in Figure 1. After initial uptake due to surface sorption, little additional Cs is removed from solution in contact with the feldspars. In contrast, parabolic uptake of Cs by obsidian continues throughout the reaction period indicating a lack of sorption equilibrium and the possibility of Cs penetration into the glass surface. 

Table II. Diffusion Coefficients for Alkali Elements in Obsidian...

The preceding data, though limited in nature, represent one of the first attempts to measure solid state diffusion rates of alkali elements into the near-surface region of feldspars and natural glasses at low temperature. As such, interesting comparisons can be made with diffusion coefficients and activation energies calculated from numerous high temperature isotope and tracer diffusion studies f 11-181. 

James RH, Palmer MR (2000b) Marine geochemical cycles of the alkali elements and boron The role of sediments. Geochim Cosmochim Acta 64 3111-3122... 

Rubidium is located between potassium and cesium in the first group in the periodic table. It is the second most electropositive alkali element and reacts vigorously and explosively in air or water. If placed on concrete on a sunny day, it would melt and then react violendy with moist air to release hydrogen with enough heat to burn the hydrogen. If a chunk of rubidium metal is left on a table exposed to the air, it combusts spontaneously. Rubidium must be stored in oil, such as kerosene. 

This attack consumes H30+ from the surrounding environment and releases alkali elements from the glass (dealkalinization). The reaction is kinetically limited by diffusion of water molecules into the bulk of the glass through the gel layer (see below). The thickness of the diffusion (or reaction) layer... 

A second method of determining major and minor element abundances in meteorites is X-ray fluorescence analysis. In this method, a sample of meteorite is ground into a fine powder and irradiated by a monochromatic X-ray beam. The atoms in the sample absorb some of the X-rays, causing electrons to be ejected. The ejection of an electron causes other electrons to drop to lower energy levels to fill the vacancy, and characteristic X-rays are emitted. The X-ray energies are unique to each element and permit the chemical composition to be determined. X-ray fluorescence was used to determine the compositions of meteorites in the late 1950s and 1960s. If done correctly the compositions have the same accuracy as wet chemical analyses, but some of the measurements in the literature have problems with alkali elements. 

Being a valuable isotope analytical technique in routine work for high precision isotope ratio measurements, TIMS is applied in many laboratories worldwide for isotope ratio measurements especially for elements with ionization potentials < 7 eV,7 such as alkali and earth alkali elements, rare earth elements (REE), uranium and plutonium. It is advantageous that the interference problem occurs relatively seldom in TIMS, especially if the negative thermal ionization technique for elements and molecules with electron affinities > 2eV (Ir, W, Os, Re, Pt, Cl and Br) is applied. TIMS with multiple ion collectors achieves a precision of up to 0.001 % thus permitting the study... 

The advantages of flame photometry are reasonably good sensitivity, convenience, and versatility. For the alkali elements it is accepted as the standard method for water samples and can give good precision under carefully controlled conditions. The sensitivity for many elements (—i.e., zinc) is poor, and there can be severe matrix problems. Not only are there many examples of enhancement and suppression by other elements, but foreign constituents as they affect the viscosity, surface tension, and volatility of the samples can affect the emission efficiency (4, 11). 

Since Na has valence of one, all other elements of the same kind (that is, the alkali elements K, Rb, Cs) also have valence of one. 

V which is near the breakdown voltage for this electrolyte and titanium. SIMS data show hydrocarbons, alkali elements, calcium, and most importantly evidence of phosphorus (probably phosphate ion) in the porous film. AES elemental profiles show that phosphorus concentrations are high at the surface and continue on into the film. 

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