Cesium concentration dependence

Viscosity of aqueous cesium chloride (CsCl) solution was measured in the range of 0.1-5.0 mol kg-i and 0.1-375 MPa at 25 °C. The Jones-Dole B coefficient of CsCl was obtained from the concentration dependence of the viscosity. It is negative not only at atmospheric pressure but also at high pressure, having a maximum against pressure at about 160 MPa. Similar maximum of the B was observed for aqueous sodium chloride (NaCl) solution. The similarity is discussed in terms of the water structure and dielectric friction theory. 

Litvin et al. (1981a, 1982) have studied the systems MjO-NdjOj-PjOj-HjO (M = K, Cs), not using an open crucible but carrying out the experiments under partial vapor pressure of water. With low cesium concentrations the products are Nd(P03)3 and NdPjOj, depending on the temperature, and with higher cesium concentrations double polyphosphates are formed. The cubic cyclophosphate, CsNdP Oj2, is formed at 350-520°C, the monoclinic polyphosphate (P2j/n) CsNd(P03) at 520-675°C, and another monoclinic polyphosphate (P2,) above 675°C. 

Table 55 presents the results discussed above. Fluoride melts containing tantalum contain two types of complex ions, namely TaF6 and TaF72 . The equilibrium between the complexes depends on the concentration of fluoride ions in the system, but mostly upon the nature of the outer-sphere cations. The complex ionic structure of the melts can be adjusted by adding cations with a certain polarization potential. For instance, the presence of low polarization potential cations, such as cesium, leads primarily to the formation of TaF72 complexes, while the addition of cations with relatively high polarization potentials, such as lithium or sodium, shifts the equilibrium towards the formation of TaF6 ions. 

There are no reports of adverse effects in humans. By analogy to NaOH, the effects from dust or mist could be expected to vary from mild irritation of the upper respiratory tract to pneumonitis, depending on the severity of the exposure. The greatest industrial hazard is rapid tissue destruction of the eyes on contact with the solid or a concentrated solution. If cesium hydroxide is not removed from the skin, it is anticipated that burns will occur after a period of time. Ingestion would be expected to cause corrosion of the lips, mouth, tongue, and pharynx, as well as abdominal pain. 

Cesium and iodide ions quench Trp residues that are present at or near the surface of the protein. The iodide ion is more efficient than the cesium ion, i.e., each collision with the fluorophore induces a decrease in fluorescence intensity and lifetime, which is not the case with cesium. Also, since cesium and iodide ions are charged, their quenching efficiency will depend on the charge of the protein surface. For free tryptophan and tyrosine in solution, the highest values of K y that we have found with iodide are 17.6 and 19 M-1, respectively, and so the corresponding kq values are 6.8 x 109 and 5.3 x 109 M-1 s-1, respectively (Figure 10.4). Ksv is calculated from the slope of the plot drawn at lowKI concentrations. 

Which ions are specifically adsorbed It depends, of course, on the metal, but detailed and accurate data are available only for mercury. As a rule, ions that are not hydrated tend to be specifically adsorbed. This includes most of the anions, but not F. Also, some highly symmetrical anions such as CIO, BF, and PF, are not specifi-cally adsorbed on mercury. Most cations are not specifically adsorbed on mercury. Cesium, which was found to be specifically adsorbed to some extent, is an exception. Also, large organic cations of the tetraalkyl ammonium type are found to be specifically adsorbed on mercury. For some ions, specific adsorption may be observed only at high concentrations, and it must always be remembered that such adsorption has been... 

Alkali metal naphthalene complexes have also been used to initiate epoxide polymerizations. Solov yanov and Kazanski [25] studied the polymerization of EO in tetrahydrofuran using sodium, potassium or cesium naphthalene as initiator. A living polymer was produced there is no chain rupture or transfer. The rate of polymerization depends on the concentration of active centres in a complex manner. The kinetic order varies from 0.23 for Na" (or 0.33 for K and Cs" ) up to full first order as initiator concentration decreases. The polymerization is first order in monomer, but deviations are observed at high concentrations. 

The metal reduction of the polycyclic system is usually carried out in an ether solvent and by an alkali metal at low temperature (—78 °C). When potassium metal is applied it is best to prepare a metal mirror. Sodium and lithium react, either directly in the form of a metal wire, or after treatment in an induction furnace. Cesium is prepared by thermolysis of cesium azide. It has recently been found that the application of an ultrasonic bath facilitates the reaction and avoids side reactions. The reaction can be carried out in a modified NMR tube or in an ESR cavity. Diamagnetic ions are prepared in extended NMR tubes to which the metal is extruded and sealed under vacuum. Reaction rates are difficult to compare as the electron-transfer process depends on various experimental conditions such as concentration, temperature, the presence of impurities, the solvent and the nature of the metal surface. It may take from minutes to days to form the first radical-anion the second step then follows and can sometimes be rather slow 10 13). 

It must be stressed that factors such as the hydration (or solvation) of the metal ion and anion effects on the extracted complex often make it difficult to predict the order of extractability for such systems. Such factors may even influence the stoichiometry of the extracted species. Thus, the simple match of the metal to the whole concept is only of limited utility. For example, potassium, rubidium and sodium nitrates are extracted in the presence of dibenzo-18-crown-6 (2) as 1 1 1 complexes. On the other hand, cesium forms a 1 2 1 sandwich complex with this crown (metal crown nitrate) in the organic phase and this affects the extraction order for the above metal ions, with the order being dependent on ligand concentration. In contrast, for picrate as the anion the composition of the extracted cesium complex is 1 1 1 (Fig. 4.8) [27]. 

Both the magnitude and the location of the ionic peak are dependent on the nature of the cation. Thus the ionic peak occurs at lower angles for cesium cations of a given concentration than for corresponding lithium cations. In addition, the magnitude of the ionic peak 1s much greater for cesium than for lithium. The ionic peak persists at elevated temperatures but disappears when the Ionomer is saturated with water. The scattering profile, however, in the vicinity of the ionic peak in the water-saturated ionomer is different from that of the parent acid copolymer. 

The separation of ammonia from interfering compounds was also based on gaseous diffusion of ammonia from an alkaline medium and absorption by an acidic medium. Walker and Shipman described the isolation of ammonia by the use of a zirconium phosphate cation exchanger. The adsorbed ammonia was displaced from the column by 1.24 M cesium chloride, then oxidized by hypochlorite, reacted with phenol to form a phenol-indophenol complex which was measured at 395 or 625 nm, depending on the concentration range. 

The bioavailability of cesium for plants depends on the pH-value of the soil (Wytten-bach et al., 1991), and is high on soils with low pH-values, as are found on moors and in forests. The bioavailability is markedly lower in soils with higher pH-values such as in farmed soils (e.g., meadows or pastures) and other agricultural soils where the pH-value is maintained at 6-8 by fertilizing. A high potassium concentration in the soil has also been shown to lead to a decrease in cesium uptake by plants (Shaw and Bell, 1991). 

Cesium levels in milk are about one-quarter to one-tenth those in the feed, and almost four-fold those in blood. Milk and blood cesium levels are strongly correlated (Heine et al., 1977) and depend on Cs concentrations in the feed. In the UK, the daily intake of cesium by humans is about 13 pg (Hamilton and Minsky, 1972). 

---