Lithium Chloride Applications and Preparation
| Jerry Huang
Lithium chloride is produced by treatment of lithium carbonate with hydrochloric acid. It can in principle also be generated by the highly exothermic reaction of lithium metal with either chlorine or anhydrous hydrogen chloride gas. Anhydrous LiCl is prepared from the hydrate by heating with a stream of hydrogen chloride.
Lithium chloride is mainly used for the production of lithium metal by electrolysis of a LiCl / KCl melt at 450 °C (842 °F). LiCl is also used as a brazing flux for aluminium in automobile parts. It is used as a desiccant for drying air streams. It is also used as a good fluxing agent in the electrolysis of metals, such as aluminum or titanium, or in the preparation of metallic powder. In more specialized applications, lithium chloride finds some use in organic synthesis, e.g., as an additive in the Stille reaction. Also, in biochemical applications, it can be used to precipitate RNA from cellular extracts.
Lithium chloride is also used as a flame colorant to produce dark red flames.
Lithium chloride is used as a relative humidity standard in the calibration of hygrometers. At 25 °C (77 °F) a saturated solution (45.8%) of the salt will yield an equilibrium relative humidity of 11.30%. Additionally, lithium chloride can itself be used as a hygrometer. This deliquescent salt forms a self-solution when exposed to air. The equilibrium LiCl concentration in the resulting solution is directly related to the relative humidity of the air. The percent relative humidity at 25 °C (77 °F) can be estimated, with minimal error in the range 10–30 °C (50–86 °F), from the following first order equation: RH = 107.93 - 2.11C, where C is solution LiCl concentration, percent by mass.
Molten LiCl is used for the preparation of carbon nanotubes, graphene and lithium niobate.
Lithium chloride has been shown to have strong acaricidal properties, being effective against Varroa destructor in populations of honey bees.