Element Lithium, Li, Alkali Metal
|From the compounds of the other alkali metals, those of lithium were distinguished by Arfvedson in 1817. Elementary lithium was first prepared in 1855 by Bunsen and Matthiessen, by the electrolysis of the chloride. |
Metallic lithium is the lightest of all solid substances; its density is 0.59, so that it floats on petroleum. It is a silver-white, somewhat tenacious metal, which does not melt below 180°, and does not volatilise even at a red heat. When heated in the air, it does not ignite until considerably over 200°, and it then burns with a white, very bright light, similar to that of magnesium. It decomposes water with evolution of hydrogen and formation of lithium hydroxide; the action is, however, much less violent than with the other alkali metals.
Like the other alkali metals, lithium forms a monovalent, colourless ion Li•, which can combine to form salts with all anions. From the ions of the other alkali metals, lithion is distinguished by its power of forming various sparingly soluble salts, which will be mentioned immediately. Lithium is not capable of forming any but monovalent ions.
|Lithium was discovered by a Swedish chemist and mineralogist Johan August Arfwedson (1792 - 1841), when he was an assistant in the laboratory of Jons Jakob Berzelius. Arfwedson was running chemical analysis of the petalite ore (LiAl(Si2O5)2) and supposed that it contains a new alkali element. He noticed that its compounds resembled the compounds of sodium and potassium; however its carbonate and hydroxide are less water soluble. Arfwedson offered the name "lithium" (Greek "lithos" meaning "stone") showing its mineral descent. He also showed that this element is found within the minerals spodumene (also called silicate pyroxene) LiAlSi2O6 and lepidolite (lithium-mica) with composition K2Li3Al4Si7O21(OH,F)3. The element was named by Sir Humphry Davy who used electrolysis on lithium oxide in 1818.|
|By its geochemical properties lithium belongs to Alkali Metals large-ion lithophile elements which also include potassium, rubidium, and caesium. Its concentration in upper continental crust is 21 g/t. Lithium is contained particularly in the minerals lepidolite KLi1,5Al1,5[Si3AlO10](F, OH)2 (Li-mica) and pyroxene spodumene LiAl[Si2O6]. As soon lithium does not form independent minerals it isomorphously replaces the potassium in rock-forming minerals. Lithium deposits are associated with rare metal-related granite intrusions with which Lithium-bearing pegmatite and hydrothermal complex deposits also containing among others various metals such as tin, tungsten, bismuth, are associated. A very special mineral, ongonite, which is magmatic topaz-rich granite with high concentrations of fluorine and water and extremely high concentration of rare earth metals, including lithium, is worth a specific mention. Brines of some strongly salt lakes are other kind of deposit.|
Lithium is one of the bioelements which always occur in living organisms. Until recently the physiological importance of this element was unexplored. In 1980 it was shown that the deficiency of lithium leads to liveweight gain deceleration. So the vital necessity of lithium has been proved.