Lithium chloride is a chemical compound with the formula LiCl. The salt is a typical ionic compound (with certain covalent characteristics), although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlorides, such as extraordinary solubility in polar solvents (83.05 g/100 mL of water at 20 °C) and its hygroscopic properties. Chemical properties The salt forms crystalline hydrates, unlike the other alkali metal chlorides. Mono-, tri-, and pentahydrates are known. The anhydrous salt can be regenerated by heating the hydrates. LiCl also absorbs up to four equivalents of ammonia/mol. As with any other ionic chloride, solutions of lithium chloride can serve as a source of chloride ion, e.g., forming a precipitate upon treatment with silver nitrate: LiCl + AgNO3 → AgCl + LiNO3 Preparation Lithium chloride is produced by treatment of lithium carbonate with hydrochloric acid. Anhydrous LiCl is prepared from the hydrate by heating in a stream of hydrogen chloride. Uses Commercial applications Lithium chloride is mainly used for the production of lithium metal by electrolysis of a LiCl/KCl melt at . LiCl is also used as a brazing flux for aluminium in automobile parts. It is used as a desiccant for drying air streams. 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. Niche uses Lithium chloride is used as a relative humidity standard in the calibration of hygrometers. At a saturated solution (45.8%) of the salt will yield an equilibrium relative humidity of 11.30%. Additionally, lithium chloride can 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 can be estimated, with minimal error in the range , 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. Lithium chloride is used as an aversive agent in lab animals to study conditioned place