Earth rubidium

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. 

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. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

Zinc (76ppm of the earth s crust) is about as abundant as rubidium (78 ppm) and slightly more abundant than copper (68 ppm). Cadmium (0.16 ppm) is similar to antimony (0.2 ppm) it is twice as abundant as mercury (0.08 ppm), which is itself as abundant as silver (0.08 ppm) and close to selenium (0.05 ppm). These elements are chalcophiles (p. 648) and so, in the reducing atmosphere prevailing when the earth s crust solidified, they separated out in the sulfide phase, and their most important ores are therefore sulfides. Subsequently, as rocks were weathered, zinc was leached out to be precipitated as carbonate, silicate or phosphate. 

The collected papers of a symposium at Dallas, April 1956, cover all aspects of the handling, use and hazards of lithium, sodium, potassium, their alloys, oxides and hydrides, in 19 chapters [1], Interaction of all 5 alkali metals with water under various circumstances has been discussed comparatively [2], In a monograph covering properties, preparation, handling and applications of the enhanced reactivity of metals dispersed finely in hydrocarbon diluents, the hazardous nature of potassium dispersions, and especially of rubidium and caesium dispersions is stressed [3], Alkaline-earth metal dispersions are of relatively low hazard. Safety practices for small-scale storage, handling, heating and reactions of lithium potassium and sodium with water are reviewed [4],... 

Only a few group 1 and 2 metal derivatives of selenolates have been structurally characterized. They are prepared with the same methods used for the thiolates.155,158 At present there are no crystal structures of lithium terphenyl selenolates. However, the potassium and rubidium salts, which are dimeric, have been structurally characterized.155 They are isomorphous, both to each other and to the closely related thiolate analogues.1533 Currently, there are no reported terphenylselenolates reported for the alkaline-earth metals. 

ISOTOPES There are 30 isotopes of rubidium, ranging from Rb-75 to Rb-98. Rb-85 is the only stable form of rubidium and constitutes 72.17% of all rubidium isotopes found in the Earth s crust. Rb-87 is radioactive (a half-life of 4.9x10 ° years) and makes up about 27.83% of the remainder of rubidium found in the Earth s crust. All the other 28 isotopes make up a tiny fraction of all the rubidium found on Earth and are radioactive with very short half-lives. 

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. 

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. 

A popular method used to date rocks is the potassium-argon method. Potassium is abundant in rocks such as feldspars, hornblendes, and micas. The K-Ar method has been used to date the Earth and its geologic formations. It has also been applied to determine magnetic reversals that have taken place throughout the Earth s history. Another method used in geologic dating is the rubidium-strontium, Rb-Sr, method. Some of the oldest rocks on Earth have been dated with this method, providing evidence that the Earth is approximately 5 billion years old. The method has also been used to date moon rocks and meteorites. 

Hagemann, R., Lucas, M., Nief, G. Roth, E. 1974. Mesures isotopiques du rubidium et du strontium et essais de mesure de l age de la mineralisation de l uranium du reacteur naturel d Oklo. Earth and Planetary Science Letters, 23, 170-176. 

Cse TUn and rubidium.—R. Bunsen and G. Kirchhoff (I860),11 while investigating the mineral waters of Durkein (Palatinate), evaporated down 40 tons of the water, and removed the alkaline earths, and lithia with ammonium carbonate. The filtrate showed the spectral lines of sodium, potassium, and lithium, and besides these, two splendid blue lines near to the blue strontium line. R. Bunsen aud G. Kirchhoff add ... 

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,... 

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 stability. 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 alkali metals such as cesium, rubidium, 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). 

Metals high in the reactivity series have proved very difficult to isolate. It was not until more recent times, through Sir Humphry Davy s work on electrolysis, that potassium (1807), sodium (1807), calcium (1808) and magnesium (1808) were isolated. Aluminium, the most plentiful reactive metal in the Earth s crust, was not extracted from its ore until 1827, by Friedrich Wohler (p. 74), and the extremely reactive metal rubidium was not isolated until 1861 by Robert Bunsen and Gustav Kirchhoff. 

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