Of alkali ion

In this context it is important to note that the detection of this land of alkali cation impurity in ionic liquids is not easy with traditional methods for reaction monitoring in ionic liquid synthesis (such as conventional NMR spectroscopy). More specialized procedures are required to quantify the amount of alkali ions in the ionic liquid or the quantitative ratio of organic cation to anion. Quantitative ion chromatography is probably the most powerful tool for this kind of quality analysis. 

The attack of most glasses in water and acid is diffusion controlled and the thickness of the porous layer formed on the glass surface consequently depends on the square root of the time. There is ample evidence that the diffusion of alkali ions and basic oxides is thermally activated, suggesting that diffusion occurs either through small pores or through a compact body. The reacted zone is porous and can be further modified by attack and dissolution, if alkali is still present, or by further polymerisation. Consolidation of the structure generally requires thermal treatment. 

With the migration of alkali ions (R ) into the leachant the attack is no longer by water. If is sodium the attack on the glass is ... 

Studies on hot water tank enamelsin media of varying pH demonstrate a minimum corrosion rate at pH value of 4. In citric acid (pH 2), IR measurements indicate that ion exchange is the principal mode of corrosion. Distilled water (pH 7) showed evidence of a bulk dissolution mechanism with no silica enrichment of the surface layer. In neutral solutions, the first stage of attack is leaching of alkali ions, raising the pH of solution, which subsequently breaks down the glass network of the acidic oxides. 

Kinetics and mechanism of alkali ion complex formation in solution. R. Winkler, Struct. Bonding (Berlin), 1972,10,1-24 (38). 

Winkler R (1972) Kinetics and Mechanism of Alkali Ion Complex Formation in Solution. W 1-24... 

In the gas phase the dipole moment determined through Eq. (4.10) refers to an individual adsorbed particle. This is not so in the electrochemical situation. The dipole moment of an adsorbed species will tend to align neighboring solvent molecules in the opposite direction, thereby reducing the total dipole potential drop (see Fig. 4.3). Only the total change in dipole potential can be measured, and there is no way of dividing this into separate contributions from the adsorbate bond and the reorientation of the solvent. The apparent dipole potential of an ion adsorbed from a solution on a particular metal is often substantially smaller than that of the same ion adsorbed in the vacuum (see Table 4.1), since it contains a contribution from the solvent. For comparison we note that the dipole moments of alkali ions adsorbed from the vacuum are usually of the order of the order of 10 29 C m. 

The terminal network sites so produced then provide a path for the easy movement of alkali ions, explaining the accompanying increase in alkali extraction. 

Non-lattice sites may play an important role in the incorporation of large foreign ions in crystal structures during coprecipitation Pingitore (Chapter 27) discusses the importance of these sites in the formation of coprecipitates of calcium carbonate containing Srz+ or Ba. White and Yee (Chapter 28) discuss the diffusion of alkali ions into defect structures in the surfaces of glasses and crystalline feldspars. 

EHM has also been applied for the calculations of optimum coordination numbers 226> in hydrated alkali ions (Table 20). The affinities of alkali ions to NN -dimethylacetamide and methylacetate were estimated by Kostetsky et al. 227>, using the CNDO/2 procedure (Table 21). As long as the ions are constrained to lie in the peptide- or ester planes, correct trends are obtained, but relaxation of this constraint reveals serious discrepancies to ab initio calculations. The CNDO procedure artificially stabilizes structures with nonpolar bonding geometries,... 

Analytes of very high polarity are not anymore ionized by field ionization. Here, the prevailing pathways are protonation or cationization, i.e., the attachment of alkali ions to molecules. [78] The subsequent desorption of the ions from the surface is effected by the action of the electric field. As [M-t-Na]" and [M-i-K] quasi-molecular ions are already present in the condensed phase, the field strength required for their desorption is lower than that for field ionization or field-induced [Mh-H]" ion formation. [37,79] The desorption of ions is also effective in case of ionic analytes. 

Fig. 8.14. The FD mass spectrum of arginine, = 174, desorbed from an untreated metal wire emitter in the presence of alkali ions. Adapted from Ref. [37] by permission. lohn Wiley Sons, 1977.

Deposition of the analyte on nitrocellulose films instead of metal foils allows the removal of alkali ion contaminations by washing of the sample layer which results in better PD spectra. [163] Further improvements can be achieved by adsorption of the analyte molecules on top of an organic low-molecular weight matrix layer. [164,165]... 

Note Carbohydrates possess a high affinity towards alkali metal ions, and thus in MALDI spectra [M-tNa] and/or [M+K] are normally observed instead of or in addition to [Mh-H]" ions of very low abundance. Radical ions are not observed. It basically depends on the relative amount of alkali ion impurities or dopant which quasimolecular ion will be dominant. 

Only with silica was the nature of the surface groups studied as extensively as with carbon. Silica, like carbon, has several polymorphs. Apart from the amorphous state, it is known to exist in numerous crystalline modifications. The most important forms are quartz, tridymite, and cristobalite. Each of these can occur in a low-temperature form and in a high-temperature form of somewhat higher symmetry. Tridymite is only stable if small amounts of alkali ions are present in the lattice 159). Ar. Weiss and Al. Weiss 160) discovered an unstable fibrous modification with the SiSj structure. Recently, a few high-pressure modifications have been synthesized keatite 161), coesite 162), and stishovite 16S). The high-pressure forms have been found in nature in impact craters of meteorites, e.g., in the Arizona crater or in the Ries near Nbrdlingen (Bavaria). 

A special feature is presented by the structures of the cryolite family, in which two different C.N.s, 6 and 12 resp., are offered to the same A-ions. This C.N. of 6, unfavourable to potassium and the larger alkali ions, is the reason why compounds of this kind often show either distortion from cubic symmetry or a deficit of alkali ions, especially if prepared from aqueous solution (77). According to the general formula Aa- MeFe- XH2O 1) some fluorine can be substituted by water in the crystal lattice. 

Gaseous chemical compounds whose molecules contain chlorine and/or fluorine - such as refrigerants R12, R22 and R134a - will influence the emissions of alkali ions from a surface impregnated with a mixture of KOH and lron(lll)hydroxide and maintained at 800 °C to 900 °C by an external Pt heater. The released ions flow to a cathode where the ion current is measured and then amplified (halogen diode principle). This effect is so great that partial pressures for halogens can be measured down to 10 mbar. 

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