Applications miners’ lamps

A convenient method is the spectrometric determination of Li in aqueous solution by atomic absorption spectrometry (AAS), using an acetylene flame—the most common technique for this analyte. The instrument has an emission lamp containing Li, and one of the spectral lines of the emission spectrum is chosen, according to the concentration of the sample, as shown in Table 2. The solution is fed by a nebuhzer into the flame and the absorption caused by the Li atoms in the sample is recorded and converted to a concentration aided by a calibration standard. Possible interference can be expected from alkali metal atoms, for example, airborne trace impurities, that ionize in the flame. These effects are canceled by adding 2000 mg of K per hter of sample matrix. The method covers a wide range of concentrations, from trace analysis at about 20 xg L to brines at about 32 g L as summarized in Table 2. Organic samples have to be mineralized and the inorganic residue dissolved in water. The AAS method for determination of Li in biomedical applications has been reviewed . 

History.—Until the middle of the eighteenth century both scheelite and wolframite were considered to be ores of tin their real identity was first pointed out in 1781 by Scheele, who show ed that the mineral now bearing his name contained lime combined with a new acid, which he named tungstic acid. The metallic nature of the element was first demonstrated by Bergman. Further researches were undertaken by D Elhuyart, Juan, Jose, and others. The preparation of metallic tungsten, its industrial application (especially with regard to electrical glow lamps), and the study of its compounds have since been the subject of numerous researches. 

For a dozen years he regularly produced a series of immensely popular lectures on the latest discoveries in and applications of chemistry. Active in research, he discovered six elements in two years (1807-1808), conclusively disproved Lavoisier s hypothesis that oxygen was present in all acids (1810), and discovered and launched Michael Faraday into a stellar chemistry career. In 1812, he was knighted and in 1815 invented the coal miner s safety lamp that saved many lives. 

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