Lithium sulfate is a white inorganic salt that contains lithium and sulfuric acid. It is soluble in water, though its solubility does not follow the usual trend of increasing solubility with temperature—instead, it decreases with temperature because the dissolution of Li2SO4 is an exothermic process. This unusual solubility property, called retrograde solubility, is shared by few other inorganic compounds.
The sulfate form of lithium has several industrial applications. It is used in a battery to power portable devices and cars, including digital watches and mobile phones. It is also used to increase the performance of lubricants and in the manufacture of glass and fiberglass. It is also useful as an operating medium for air-conditioning systems and a deliquescent solvent. It is also used as a sedative and hypnotic in medicine and to produce other lithium chemicals and organic compounds.
It is widely present in natural waters. It is also found in soil and can be absorbed by plants at high concentrations, such as the nightshade Solanum dulcamera, which may reach levels up to three- to sixfold greater than other species. It can also be absorbed by bacteria, such as the strains Arthrobacter nicotianae and Brevibacterium helvovolum, which can cause plant disease when the concentration of this element in the soil reaches
A recent method for extracting lithium from natural spodumene has been developed using hot digestion of the roasted material to convert a-spodumene to b-spodumene and then treating it with concentrated sulphuric acid at 250 degC, followed by water leaching and carbonate precipitation to separate the lithium as Li2CO3. This new process has the potential to be applied to other micas such as lepidolite, amblygonite, and zinnwaldite.