Rubidium occurrence

Rubidium Analysis, Biological Studies and Occurrence," Chemical Abstracts— Chemical Substances Indexes, American Chemical Society, Washington, D.C. 

Occurrence.—Rubidium is widely distributed in nature, being found in small quantities in association with the other alkali-metals. It constitutes about 1 per cent, of lepidolite, and is present in the Stassfurt salt deposits, in the soil, in many natural waters, and in the ashes of numerous plants. 

The history of atomic emission spectrometry (AES) goes back to Bunsen and Kirchhoff, who reported in 1860 on spectroscopic investigations of the alkali and alkali earth elements with the aid of their spectroscope [1], The elements cesium and rubidium and later on thorium and indium were also discovered on the basis of their atomic emission spectra. From these early beginnings qualitative and quantitative aspects of atomic spectrometry were considered. The occurrence of atomic spectral lines was understood as uniequivocal proof of the presence of these elements in a mixture. Bunsen and Kirchhoff in addition, however, also estimated the amounts of sodium that had to be brought into the flame to give a detectable line emission and therewith gave the basis for quantitative analyses and trace determinations with atomic spectrometry. 

The danger of rubidium exposure caused by geological or anthropogenic anomalies hardly exists. The occurrence of the naturally radioactive Rb isotope (27.8%) is interesting at least (Anke and Angelow 1995). 

Thallium is a rare element which occurs in the Earth s crust at an estimated abundance of 0.1 to 0.5 ligg (see Part I, Chapter 1). The specific ionic properties of thallium (e.g., ionic radius Tl 0.147 nm) are similar to those of potassium and rubidium (ionic radius K 0.133 nm, Rb" 0.147 nm) thus, thallium occurs ubiquitously as a trace element within the environment, mainly in association with K and Rb. Besides its occurrence in widespread potassium compounds, thallium is a trace component in iron, zinc, copper, and lead minerals (Nriagu 1998). 

Dopant uptake is much higher in this case, y = 0.85, which implies a Cs -Cs spacing of Si 3.9 A. The authors point out, in a comparison with the structures found in doped polyacetylene, that the occurrence of either three-fold or four-fold column structures depends on the size ratio of the projected polymer chain (Totor dimension ) and the ion. In polyacetylene, Na ions leads to three-fold columns as in PPV, but for doping the columns in polyacetylene are formed by four chains, in contrast to the result for PPV. This is because the rotor size of a polyacetylene chain is smaller than that of PPV (Table 1.7). Rubidium doping of PPV represents an intermediate case, for which, apparently, neither three-fold nor four-fold... 

An analogous reaction in rubidium suffices to explain the observations of Lawrence and Edlefsen. Subsequent investigations by Mohler and Boeckner and Freudenberg were consistent with the occurrence of (11), a homonuclear associative ionization reaction. 

Rubidium is widely distributed in the earth s crust with no single mineral source. Its most concentrated occurrence is in the lithium mica lepidolite (lithium aluminosilicate) where its concentration may vary from 0 to 3.5% Rb20 (average 0.5%). This source, as a byproduct of the production of lithium, offers the largest and cheapest supply [5,6]. The metal is obtained by electrolysis of the fused chloride out of contact with air [7]. 

A study published quite some time ago reviewed the soil-cancer relationship for gastric, esophageal, urinary, breast, bone, and bronchial cancers as well as pleural mesothelioma. In addition to general factors, the study considered trace elements including selenium, cesium, and rubidium potassium and natural radioactivity. Although some correlations between soil constituents and cancer have been observed, the cause and effect relationship between soil characteristics and occurrence of cancer could not be proved definitively. 

Rubidium.—Bb, a.n. 37 a.w. 85 45. Sheldon and Bam e (1931) find rubidium as a constant micro-constituent in aU human tissues, but its occurrence in lower animals and plants is very sporadic. The metal is closely related to potassium, and Bubenstein reports that marine diatoms and possibly some of the seed plants can replace Bb+ for K+ in cell growth. Higher animals cannot survive such substitutions. The rubidium content of sea water is assessed by Schmidt at 10-15 mg. per litre, a value that is almost certainly excessive in view of the fact that Ramage finds that marine animals never contain more Bb than 0 002 per cent, of their dry weight. 

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