Earth cesium

Monazite (white)—RARE EARTHS cesium, lanthium, neodymium, thorium... 

The element is much more abundant than was thought several years ago. It is now considered to be the 16th most abundant element in the earth s crust. Rubidium occurs in pollucite, leucite, and zinnwaldite, which contains traces up to 1%, in the form of the oxide. It is found in lepidolite to the extent of about 1.5%, and is recovered commercially from this source. Potassium minerals, such as those found at Searles Lake, California, and potassium chloride recovered from the brines in Michigan also contain the element and are commercial sources. It is also found along with cesium in the extensive deposits of pollucite at Bernic Lake, Manitoba. 

Potassium acetate, mbidium acetate, and cesium acetate are very soluble ia anhydride ia contrast to the only slightly soluble sodium salt. Barium forms the only soluble alkaline earth acetate. Heavy metal acetates are poorly soluble. 

Time. The unit of time in the International System of units is the second "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental state of the atom of cesium-133" (25). This definition is experimentally indistinguishable from the ephemetis-second which is based on the earth s motion. 

Rubidium [7440-17-7] Rb, is an alkali metal, ie, ia Group 1 (lA) of the Periodic Table. Its chemical and physical properties generally He between those of potassium (qv) and cesium (see Cesiumand cesium compounds Potassium compounds). Rubidium is the sixteenth most prevalent element ia the earth s cmst (1). Despite its abundance, it is usually widely dispersed and not found as a principal constituent ia any mineral. Rather it is usually associated with cesium. Most mbidium is obtained from lepidoHte [1317-64-2] an ore containing 2—4% mbidium oxide [18088-11-4]. LepidoHte is found ia Zimbabwe and at Bernic Lake, Canada. 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

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). 

Other recent works in this field, studies on the transport of alkali and alkaline earth cations with p-zerr-butyl calix[n]arene esters and amides, were carried out by Arnaud-Neu et al. [20] and Casnati et al. [21]. They prepared 1,3-alternate calix[4]arene-crown-6 as a new class of cesium selective ionophore. 

The catalyst (spheres or rings with a diameter of 3-10 mm) contains 7-20% silver on high-purity a-AI203 having a surface of only <2 m2/g. Cesium or another alkali or earth alkali salt is added in an amount of 100-500 mg/kg catalyst for upgrading the selectivity. However, small amounts of halogen compounds, e.g., dichloroethane, are added to the ethylene/oxygen mixture to inhibit the total oxidation of the ethylene. 

Rubidium does not exist in its elemental metallic form in nature. However, in compound forms it is the 22nd most abundant element on Earth and, widespread over most land areas in mineral forms, is found in 310 ppm. Seawater contains only about 0.2 ppm of rubidium, which is a similar concentration to lithium. Rubidium is found in complex minerals and until recently was thought to be a rare metal. Rubidium is usually found combined with other Earth metals in several ores. The lepidolite (an ore of potassium-lithium-aluminum, with traces of rubidium) is treated with hydrochloric acid (HCl) at a high temperature, resulting in lithium chloride that is removed, leaving a residue containing about 25% rubidium. Another process uses thermochemical reductions of lithium and cesium ores that contain small amounts of rubidium chloride and then separate the metals by fractional distillation. 

ISOTOPES Cs-133 is the only stable isotope of cesium, and it makes up all of the naturally occurring cesium found in the Earth s crust. In addition to Cs-133 there are about 36 radioactive isotopes of Cs, most of which are artificially formed in nuclear reactors. All are produced in small numbers of atoms with relatively short half-lives. The range of Cs isotopes is from Cs-113 (amu = 112.94451) to Cs-148 (amu = 147.94900). Most of these radioisotopes produce beta radiation as they rapidly decay, with the exception of Cs-135, which has a half-life of 3x10 yr, which makes it a useful research tool. Cs-137, with a half-life of 33 years, produces both beta and gamma radiation. 

Like the other alkali metals, cesium is a soft-solid silvery metal, but much softer than the others. It is the least electronegative and most reactive of the Earth metals. Cesium has an oxidation state of +1, and because its atoms are larger than Li, Na, and K atoms, it readily gives up its single outer valence electron. The single electron in the P shell is weakly attached to its nucleus and thus available to combine with many other elements. It is much too reactive to be found in its metallic state on Earth. 

Francium s atoms are the largest and heaviest of the alkali metals in group 1 (lA). It is located just below cesium on the periodic table, and thus it is assumed to be an extremely reactive reducing agent even though it is the most scarce of the alkali metals. Its most stable isotope (Fr-223) exists for about 21 or 22 minutes. No one has figured out how to refine francium from natural minerals (ores) because the atoms of the most stable isotope found in nature (Fr-223) are scattered very thinly over the Earth s crust. All of the other 30 isotopes are produced for study by nuclear decay of other radioactive elements. 

Trace element retention on earth materials is illustrated in several case studies, where selected contaminants (e.g., fluoride, cesium, mercury) interact with rocks, clays, soils, and sediments under different environmental conditions (e.g., pH, presence of organic ligands, salinity). 

In Figure 5-13, you can see that the most electronegative element is fluorine. The nonmetals in the upper right corner have a strong tendency to gain electrons. The element of lowest electronegativity is cesium (Cs), in the lower-left corner. The relatively weak attraction for electrons by the alkali metals and alkaline earths is responsible for the loss of electrons by those elements. 

Cesium was discovered by Bunsen and Kirchoff in 1860. It is found in the minerals pollucite, lepidolite, and the borate rhodizite. Pollucite, CsAlSi206, is a hydrated silicate of aluminum and cesium. The concentration of cesium in the earth s crust is estimated to be 3 mg/kg, and in sea water 0.3pg/L. 

Rubidium is widely distributed in nature. Its abundance in the earth s crust is estimated to be 90 mg/kg. Rubidium occurs at trace levels in many potassium minerals. Often it is associated with cesium. Some rubidium-con-... 

Many elements are present in the earth s crust in such minute amounts that they could never have been discovered by ordinary methods of mineral analysis. In 1859, however, Kirchhoff and Bunsen invented the spectroscope, an optical instrument consisting of a collimator, or metal tube fitted at one end with a lens and closed at the other except for a slit, at the focus of the lens, to admit light from the incandescent substance to be examined, a turntable containing a prism mounted to receive and separate the parallel rays from the lens and a telescope to observe the spectrum produced by the prism. With this instrument they soon discovered two new metals, cesium and rubidium, which they classified with sodium and potassium, which had been previously discovered by Davy, and lithium, which was added to the list of elements by Arfwedson. The spectroscopic discovery of thallium by Sir William Crookes and its prompt confirmation by C.-A. Lamy soon followed. In 1863 F. Reich and H. T. Richter of the Freiberg School of Mines discovered a very rare element in zmc blende, and named it indium because of its brilliant line in the indigo region of the spectrum. 

By careful choice of the storage material, catalysts with differing storage capacities and thermal properties can be designed for applications with different temperature ranges. Typical adsorber materials are the alkali and alkaline-earth metal oxides, e.g. barium, magnesium, potassium and cesium. 

The agreement between these two tests indicated no significant change in leach rate with time on this short time scale, for the particular elements studied ( i.e.j barium, strontium, cerium, and rare earths). It was not possible to determine the cesium content in these granules because, for economy reasons, cesium was not included in the calcine production. The results of these measurements are given in Table III. Significant differences in the leach rates of the alkaline earths (barium, strontium) the RE (europium), and cerium are observable. 

Heterobinuclear complexes containing alkali or alkaline earth metal cations have been derived from mononuclear transition metal complexes of compartmental ligands (51).288 The molar conductivities of the (51)-CuLi2 series suggest that the complexes are uniunivalent electrolytes in water and so are present in solution as Li[(51b)CuLi]- H20 the corresponding di-sodium, -potassium or -cesium complexes are unibivalent electrolytes and so likely to be present in solution as M2[(51)Cu]- H20. 

Alum, KAl(S0i)i-l2H20.—Ammonium, rubidium, cesium, univalent thallium, and in some cases sodium may replace potassium, while the aluminum may be replaced by trivalent iron, chromium, indium, gallium, titanium, vanadium but not by the rare-earth metals. 

Olher mudern getter materials include cesium-rubidium alloys, tantalum. titanium, zirconium, and several of the rare-earth elements, such as hafnium,... 

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