|Molecular formula||Li 2 CO 3|
|External identifiers / databases|
|Molar mass||73.89 g mol −1|
2.11 g cm −3
720 ° C
1310 ° C (decomposition)
|ΔH f 0||
−1215.9 kJ / mol
|As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .|
Lithium carbonate (technical language) or lithium carbonate (Li 2 CO 3 ) is the lithium salt of carbonic acid . Lithium carbonate is the most important lithium compound. As early as 1985, world sales of lithium carbonate were around 28,000 tons / year.
Lithium carbonate occurs very rarely in nature in the form of the mineral zabuyelite .
Extraction and presentation
The lithium-containing ore is crushed, roasted to remove organic impurities and digested with sulfuric acid . By adding sodium carbonate (soda), the impurities are first precipitated and filtered off. Further alkalization with sodium carbonate leads to the precipitation of lithium carbonate, which is filtered off or centrifuged off. If the starting material is heavily contaminated, it is dissolved again with sulfuric acid and precipitated with sodium carbonate. Before packaging, the lithium carbonate is dried in a vacuum dryer .
By reacting with carbon dioxide, the water-insoluble lithium carbonate is converted into the metastable lithium hydrogen carbonate (lithium bicarbonate). After the aluminum and iron silicates have precipitated, the lithium hydrogen carbonate is collected and converted back into pure lithium carbonate by heating to 95 ° C.
The processing of brines containing lithium is more economical. They are concentrated before they are precipitated with soda. In the Salar de Atacama extraction area in Chile , this occurs partly through evaporation of the water in solar ponds . The subsequent production process takes place as described above.
Lithium carbonate crystallizes in the monoclinic crystal system in space group C 2 / c (space group no. 15) with the lattice parameters a = 835.9 pm , b = 497.67 pm, c = 619.4 pm and β = 114.72 °. In the unit cell contains four formula units . Phase transitions take place at 350 ° C and 410 ° C. In contrast to the carbonates of the other alkali metals , lithium carbonate is less soluble in water. The solubility decreases with increasing temperature. Therefore, the conversion of aqueous lithium salt solutions with sodium carbonate is a suitable manufacturing method :
This solubility behavior is used in the laboratory to purify commercially available lithium carbonate. For this purpose, a cold-saturated solution is prepared, insoluble impurities are filtered off if necessary and then heated to the boil with vigorous stirring. Due to the decreasing solubility of lithium carbonate with increasing temperature, pure lithium carbonate begins to precipitate, which is then filtered off while hot.
If lithium carbonate is heated in an electric furnace with an excess of carbon , lithium carbide is formed . Here, too, lithium is more like calcium than the other alkali metals, which are reduced to metal under these circumstances.
The standard enthalpy of formation of the crystalline lithium carbonate is Δ f H 0 298 = −1215.87 kJ / mol.
Half of the sales are required for the production of aluminum ( melt flow electrolysis ). Further areas of application are the glass , ceramic and enamel industries . Lithium carbonate ensures a lower melting temperature - which lowers energy costs - and gives the hot glass mass a lower viscosity (which, for example, facilitates the production of very thin-walled glass).
Lithium carbonate can be used as a starting material for the production of other lithium compounds such as lithium chloride , lithium formate , lithium hydroxide or lithium niobate . It is also used to lower the melting point in the electrolytic production of aluminum . Lithium-containing glasses are used to manufacture refractory glasses due to their low expansion coefficient . It is also part of quick-setting cements and screeds and serves the rapid setting of the cement. In molten carbonate fuel cells it is part of the electrolyte . In industry it is also used as a flux for the production of glass, ceramics and enamel.
In lithium therapy , lithium carbonate is used to treat depressive illnesses , manias or bipolar disorders . Trade names are for example in Germany Hypnorex and Quilonum in Austria Neurolepsin and Quilonorm , Switzerland Quilonorm . The dosage must be adjusted carefully, however, as lithium compounds can cause cardiac irritation at higher concentrations or fatal from five grams.
Lithium carbonate is the namesake of the song Lithium by the grunge band Nirvana . The song alludes to the substance's use in treating depressive disorders. The band Evanescence also released a song called Lithium in 2006 , as did the producer Venetian Snares in 2004 with the song Li2CO3 .
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