Lithium
Lithium is an alkali metal element that has an atomic number of 3, an atomic weight, 6.941, and is denoted by the atomic symbol, Li. It is a silver-white metal that melts at 356.9°F (180.5° C) and boils at 2447.6°F (1342° C). It is the least dense of the metals, with a specific gravity of 0.534. Because it has the highest specific heat of any solid element, it is sometimes used as a heat transfer agent.
The story of lithium's discovery begins in 1800, with a report by a Brazilian scientist about two new minerals he discovered while traveling in Sweden. The scientist, Jozé Bonifácio de Andrada e Silva, called the two minerals petalite and spodumene. For nearly two decades, mineralogists doubted de Andrada's reports. Then, in 1817, the two minerals were re-discovered by the Swedish chemist E. T. Svedenstjerna. Analysis of the two minerals began immediately, but produced puzzling results. Anywhere from 1 to 10 percent of the minerals was unaccounted for. Scientists could not understand why their results were so inconsistent.
The explanation for this problem was provided by Johan August Arfvedson, a young man of 25 working in Jöns Berzelius 's laboratory. When Arfvedson tried to analyze petalite and spodumene, he obtained results similar to those of others. The components he was able to identify in the former mineral, for example, added up to 95 percent or 105 percent, but never to 100 percent. He finally concluded that these results could only be explained by the presence of a new element in the mineral. He announced this finding in the Annals of Chemistry of Physics in 1819 and suggested the name lithium for the new element. The name comes from the Greek word lithos, for "stone."
We now know that petalite is a double silicate of lithium and aluminum with the formula LiAl(Si2O5)2. Arfvedson was never able to isolate the pure metal itself. That task was accomplished by W. T. Brande (1788-1866) and Humphry Davy, working independently in 1818. Both obtained the metal by electrolyzing lithium oxide.
By 1855, Robert Bunsen and Matthiessen had found a way to produce the metal in large quantities and could manufacture a few grams of it in a matter of minutes. Although lithium's name reflects the connection that early scientists made with minerals, researchers soon found the element in both plants and animals. In 1860, Gustav Kirchhoff and Bunsen found lithium in the ash of grapes, tobacco, and kelp and in milk. Later researchers also found the element in human urine, bones, and teeth.
Lithium has a great many commercial uses. It is added to some alloys as a hardening agent, especially those used in bearings. It is also added to some types of steel as a "scavenger," a substance that combines with oxygen or nitrogen in the molten state. It is also used as a scavenger in vacuum tubes.
Lithium compounds are used in photography, enamels, glasses, alkaline storage batteries, and the manufacture of jet and rocket fuels. A number of lithium compounds have important pharmacological effects. They help control the wild mood swings from depression to elation observed in manic-depressive patients. Lithium carbonate has been used for this purpose for more than three decades, and the acetate, chloride, citrate, and sulfate have similar effects. Lithium compounds have also been used as thickeners to convert oils into lubrication greases.
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