Cesium-activity

This reaction has been used to make crystalline triphenylmethyl derivatives that have been characterized by X-ray structure determinations,22 and a technique has been developed for the reduction of hydrocarbons by liquid cesium activated by ultrasound irradiation in the presence of ethers such as diglyme.23 The blue solutions obtained when cesium metal is dissolved in THF in the presence of [18]-crown-6 have been used to metallate a series of 1,4- or 1,5-hexadienes. The organocesium compounds have not been isolated but they have been identified by derivatization by carbonation and trimethylsilylation.24 Substituted cyclopentadienyl derivatives of sodium have also been synthesized by this method.25... 

The increasing threat of international terrorism was one motivation for development of ISE for the determination of Cs+ in environmental samples [80]. In an event such as a Chernobyl-type disaster or the explosion of a dirty bomb , cesium is one of the most important reaction products and is expected to be the most significant threat to public health [81]. With a detection limit of 10 8M, the developed electrode is sensitive enough for this application and the successful detection of cesium activities in spiked water samples has been demonstrated (see Procedure 2 in CD accompanying this book). In addition, the electrode shows excellent selectivity to cesium in the presence of high levels of strontium, an important interferent originating from nuclear explosions. 

A potassium ion-selective electrode is used to measure the concentration of potassium ion in a solution that contains 6.0 X 10 M cesium (activity). From Table 13.3, the electrode responds equally to either ion (i KCs = ) If the potential versus a reference electrode is —18.3 mV for a 5.0 X 10 M KCl solution and +20.9 mV in the sample solution, what is the activity of K in the sample Assume Nemstian response. 

Similar Cs behavior was found in different (heather, honeydew, mixed meadow and honeydew) honey samples collected in Germany (Table 10.5), as well as in mixed meadow/chestnut and honeydew honey samples collected in Slovenia (Table 10.6). Different cesium activities have been found for the same year for the same or very similar types of honey in both countries. Such results could be explained by the fact that samples of honey were collected from different locations, locations that have been contaminated differently by cesium during the main fallout events in the past. The Cs activities found in the honey of heather plants (Calluna vulgaris) are significantly higher than in honeydew honey. Heather is considered to be an excellent cesium pollution indicator, and so apparently is... 

Cesium activated catalyst is used to give stack emissions of 150 ppm SO2 as against the 500-700 ppm permitted by the Environment Protection Agency of USA. 

In the case that the conventional process of conversion of sulfur dioxide is adopted, the conversion of sulfur to sulfur trioxide as described in Sect. 11.2 can be carried out at a pressure slightly above atmospheric pressure to overcome a pressure drop in conversion and absorption. However, due to the availability of pure sulfur dioxide using a cesium activated catalyst, a higher strength of sulfur trioxide cau be produced. This will reduce air flow and lower operating costs. 

Production of NEA GaAs requires cleaning and cesium-activation procedures [5,97]. All steps are performed under ultrahigh vacuum (oxygen-free) conditions after a system bakeout. 

The sodium present in the tank in which the accident occurred comes from the primary cooling circuit of Rapsodie. After the final shutdown of the reactor, in 1982, all 37 metric tons of primary sodium were drained in 1985, then filtered to be purified from most of their radioactive contamination the 137 cesium activity, for instance, was reduced to about one hundredth of its original value. 

It can be assumed that the radioactive cesium isotopes are present in the coolant as Cs" ions, but as yet there is no direct experimental proof of this assumption. Very low cesium activities which are occasionally detected in filtered suspended corrosion products are probably attached by occlusion or by adsorption at the surfaces of the solids. Since cesium is not able to form insoluble compounds in the primary coolant, it does not participate noticeably in the contamination buildup on the primary circuit surfaces. 

In summary, modifications to the generally practiced DCDA process are primarily the use of cesium activated catalyst an additional fifth pass to increase conversion efficiency, the use of twin oleum tower system and replacing PHE s by special alloy steel heat exchangers, an efficient acid distribution system, and PTFE lined piping for acid circulation. 

Potassium Graphite. Potassium, mbidium, and cesium react with graphite and activated charcoal to form intercalation compounds CgM, C24M, C gM, C gM, and C qM (61,62). Potassium graphite [12081 -88-8] 8 P gold-colored flakes, is prepared by mixing molten potassium with graphite at 120—150°C. 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

Silver alone on a support does not give rise to a good catalyst (150). However, addition of minor amounts of promoter enhance the activity and the selectivity of the catalyst, and improve its long-term stabiHty. Excess addition lowers the catalyst performance (151,152). Promoter formulations have been studied extensively in the chemical industry. The most commonly used promoters are alkaline-earth metals, such as calcium or barium, and alkaH metals such as cesium, mbidium, or potassium (153). Using these metals in conjunction with various counter anions, selectivities as high as 82—87% were reported. Precise information on commercial catalyst promoter formulations is proprietary (154—156). 

Values of the distance of closest approach derived from experimental values of the activity coefficients are given in column 2 of Table 40. It will be seen that for the lithium and sodium salts the value is greater than the crystal-lattice spacing (given in column 4) by rather more than 1 angstrom, as is expected. For the salts of cesium, rubidium, and potassium, on the other hand, the distance of closest approach... 

In Table 40 the values for the cesium salts show that, if a zero value or a positive value of the activity /l-cocflicient is used, approximate agreement with experiment can be obtained only by introducing a value of a that is smaller than the lattice spacing in the crystal- an impossibly small value. Figure 74 indicates that this situation may have arisen because a mutual attraction between the Cs+ ion and the halide ion is superimposed on their electrostatic attraction. We may tentatively look for the source of this additional attraction in the situation depicted in Fig. 69. 

Table i. Active and selective transport of sodium, potassium and cesium ions with synthetic ionophores ... 

Many other cyclic and noncyclic organic carriers with remarkable ion selectivities have been used successfiilly as active hosts of various liquid membrane electrodes. These include the 14-crown-4-ether for lithium (30) 16-crown-5 derivatives for sodium bis-benzo-18-crown-6 ether for cesium the ionophore ETH 1001 [(R,R)-AA -bisd l-ethoxycarbonyl)undecyl-A,yVl-4,5-tctramcthyl-3,6-dioxaoctancdiamide] for calcium the natural macrocyclics nonactin and monensin for ammonia and sodium (31), respectively the ionophore ETH 1117 for magnesium calixarene derivatives for sodium (32) and macrocyclic thioethers for mercury and silver (33). 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

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