Cesium reducing properties

Potassium, Pubidium, and Cesium idjdrides. Although all the other alkah metal hydrides have been synthesized and some of the properties measured, only potassium hydride [7693-26-7] is commercially available. KH is manufactured in small amounts and sold as a mineral oil dispersion. It is a stronger base than NaH and is used to make the strong reducing agent KBH(C2H )2 and the super bases RNHK and ROK (6). 

Luo et al.90 have described yet another approach to reducing the impact of ion exchange in metal ion extraction by neutral extractants in ILs, one which relies on modifying neither the structure of the IL nor the properties of the extractant. Instead, a sacrificial species that transfers in preference to the IL cation upon metal ion extraction (thereby reducing loss of the IL) is added to the IL phase. Ideally, the sacrificial species should exhibit no affinity for the extractant (in order not to interfere with extraction of the metal ion of interest) and be more hydrophilic than the IL cation (in order to favor its loss to the aqueous phase upon metal ion transfer). Tests with sodium tetraphenylborate indicate that its addition to a solution of a calix-crown ether in [C4mim+][Tf2N ] reduces the loss of the IL induced by cesium extraction by nearly one-quarter with no adverse effect on the efficiency of cesium extraction. 

Concrete is a cheap fire and corrosion resistant material. However, active species, especially easily soluble ions such as cesium, can be leached from it by water. Addition of plastic binders to the concrete in order to improve its properties have been suggested. In the continuous bitumen extruder process for semi-liquid wastes all water is directly eliminated, considerably reducing the waste volume. The bitumen mixture is placed in steel drums of standard size (150-2001). When additional shielding is desired, the filled drums are placed into disposable or reusable sleeves of concrete, iron, or lead. Such a sleeve of 12 cm lead weighs 7 t, and reduces the surface dose rate by a factor of —10. A typical unshielded bitum i drum may have a surface dose rate of 1 Sv h necessitating remote handling. 

The reaction of benzene with cesium and cesium alloys to form cesium benzenide is remarkable. In contrast benzene in 0.01 M solution in 2 1 by volume of THF and 1,2-dimethoxyethane with Na-K alloy according to ESR analysis gave (59) concentrations of radical anion at equilibrium of 10 to 10" M as the temperature decreased from -20° to -83 . The superior reducing power of cesium and its alloys was perhaps to be anticipated in view of the superior reducing power of cesium over potassium in aqueous solution and the appreciably lower ionization potential of cesium compared to potassium in the gas phase. These properties will be influenced by differential solvation of potassium and cesium ions by tetrahydrofuran and by the nature of the ion pairs produced. For 9-fluorenyl salts the fraction of solvent-separated ion pairs has been shown (52) to decrease rapidly in the order Li > Na > K > Cs and is a sensitive function of the solvating power of the medium. The cesium salt of fluorene in THF at -70°C has been shown to exist essentially entirely as contact ion pairs whereas the sodium and lithium salts were completely solvent-separated. The reluctance of cesium cations to become solvent-separated from counteranions means that cesium ions are available for strong electrostatic interaction with anions. 

Values of / , along the saturated liquid-vapor coexistence curve of liquid cesium and rubidium are shown in a reduced plot as a function of the reduced temperatures in Fig. 3.18. It is clear once again that the two alkali metals behave very similarly close to the critical temperature, suggesting the possibility that the alkalis obey a law of corresponding states. The properties of cesium and rubidium and, in particular, the mechanism of the MNM transition are similar in many respects and we might suspect that the interparticle forces are of similar form for these... 

Cesium acid heteropolys alts (CsHPA) One interesting modification of the HPA is the partial substitution with Cs, especially in the case of 2.5 atoms, where the surface acidity achieves its maximum [39, 48, 49]. The water solubility of the salt is reduced and the surface area increased, maximizing the interaction with the polymer matrix. The use of a phosphorous-based salt of this type maximizes the membrane conductivity, whereas the silica-based salt reinforces the mechanical properties. Very interesting results are also obtained when W was replaced by Mo [49]. 

Many other inorganic materials such as Caj (PO ), BPO, ZrPO, etc., when blended with Nafion membranes will show improvement on the membranes properties such as thermal stability, proton conductivity, and lower methanol permeation. Nafion doped with cesium cations also show evidence of good performance in the operation of DMFCs. The presence of cesium ions in the membrane, specifically in the water-rich domains, causes a ranarkable reduction of methanol permeation [43]. However, the proton conductivity could be depressed to a lesser extent by the presence of the cesium ions in the membrane. Nevertheless, at ambient conditions, the combined parameter of both proton conductivity and methanol permeabiUty shows better performance of Cs -doped membranes than the Nafion 117 membranes in the operation of DMFC. Table 15.1, shows permeability values for Nafion 117 membrane and four different Nafion 117 modified membranes. A reduction in the permeability values when the Nafion 117 membrane is modified with appropriate methanol inhibiting material can be seen. A very sharp reduction is particularly noticed in the case of Cs -doped manbrane. This indicates that exchange of by Cs cations is very effective in reducing methanol content in the hydrophilic domains of Nafion. 

Graphite reacts with alkali metals - potassium, cesium and rubidium - to form lamellar compounds with different stoichiometries. The most widely known intercalate is the potassium-graphite which has the stoichiometry of CgK. In this intercalate the space between the graphite layers is occupied by K atoms. CgK functions as a reducing agent in various reactions such as reduction of double bonds in a,fl-unsaturated ketones [19], carboxylic acids and Schiff bases alkylation of nitriles [20], esters and imines [21] reductive cleavage of carbon-sulfur bonds in vinylic and allylic sulfones [22]. The detailed reaction mechanism of CgK is not known, and the special properties which are ascribed to the intercalate come either from the equilibrium between K+/K [23], or topochemical observations (the layer structure) [24]. 

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