What Is Lithium Chloride (LiCl)?
Lithium chloride, written as LiCl, is an inorganic halide salt registered under CAS number 7447-41-8 and EINECS 231-212-3. It is a white, crystalline, strongly hygroscopic solid that crystallises in the cubic rock-salt lattice. Because the lithium ion is small and highly polarising, LiCl dissolves readily in water and in polar organic solvents such as methanol, ethanol, acetone and pyridine, and dissolution in water is strongly exothermic.
Anhydrous LiCl and its hydrates are handled as different products. The anhydrous grade carries an assay of 99.0% or higher and is the form used in molten-salt electrolysis, aluminium brazing flux and organic synthesis, while the monohydrate is common in general laboratory and humidity-control work.
Physical and Chemical Properties
| Property | Typical value |
|---|---|
| Chemical formula | LiCl |
| CAS number | 7447-41-8 |
| Molar mass | 42.39 g/mol |
| Appearance | White crystalline solid or powder |
| Density | about 2.07 g/cm3 |
| Melting point | about 605 C |
| Boiling point | about 1382 C |
| Solubility in water at 20 C | about 83 g per 100 mL |
| Crystal structure | Cubic, rock-salt type |
Two properties dominate industrial practice: the high water affinity, which makes the salt an efficient desiccant and at the same time demands moisture-barrier packaging, and the low melting point of LiCl-KCl mixtures, which is the basis of lithium metal electrolysis.
Lithium Metal Production by Molten Salt Electrolysis
The largest industrial outlet for lithium chloride is the production of lithium metal. A molten LiCl-KCl mixture is electrolysed at roughly 450 C, well below the 605 C melting point of pure LiCl, which lowers cell voltage and specific energy consumption. Lithium metal deposits at the cathode and chlorine is released at the anode.
Metal obtained by this route feeds lithium-ion battery materials, aluminium-lithium alloys, high-performance lubricating greases and organolithium reagents. Electrolysis cells demand dry feed and tight moisture control, because residual water hydrolyses the melt and carries hydroxide and oxide into the electrolyte bath, which lowers current efficiency.
Brazing Flux and Dehumidification Applications
In automotive and HVAC manufacturing, LiCl-bearing flux systems are used when aluminium components are brazed. The flux attacks and removes the surface oxide film so that filler metal wets and flows, producing sound joints without mechanical abrasion. Flux loading and furnace atmosphere must be controlled to avoid corrosive residue on the finished assembly.
Anhydrous LiCl is also used in liquid-desiccant dehumidifiers, where brine is circulated over a contact surface and the diluted solution is continuously regenerated by heating. Such systems run at moderate temperatures and suit warehouses, coating lines and food processing areas that need stable relative humidity without the condensation problems of chilled-coil drying.
Organic Synthesis, Biochemistry and Laboratory Uses
Lewis acid catalyst and additive in Diels-Alder, Michael addition and esterification reactions.
Reagent for preparing organolithium compounds and for halogen-metal exchange.
Precipitation of RNA from cellular extracts in molecular biology protocols.
Molten LiCl flux in the preparation of lithium niobate, graphene and carbon nanotube materials.
Electrolyte component in electrochemical cells and in humidity-standard solutions used for calibration.
Grades, Packaging and Storage
Commercial grades include technical, industrial and high-purity anhydrous LiCl, plus the monohydrate. Because the solid is hygroscopic, it is packed in moisture-barrier liners inside fibre drums or in sealed polyethylene bags, and net weight is normally declared on a dry basis. Store the material in a dry, closed warehouse away from strong acids and oxidising agents, and reseal opened containers immediately after sampling.
Handling follows standard chemical hygiene rules. Inhalation and ingestion must be avoided, eye and skin protection is required, and dusty operations should be carried out with local exhaust ventilation. Spent solutions are neutralised and disposed of in line with local environmental regulations.
Frequently Asked Questions
Q: What is the chemical formula of lithium chloride?
The formula is LiCl, with a molar mass of 42.39 g/mol and CAS number 7447-41-8.
Q: What is lithium chloride used for?
Its main uses are lithium metal production by molten salt electrolysis, aluminium brazing flux, liquid-desiccant dehumidification, catalysts and organolithium synthesis, and RNA precipitation in laboratories.
Q: Is lithium chloride soluble in water?
Yes. About 83 g dissolves in 100 mL of water at 20 C, and the dissolution releases heat because it is exothermic.
Q: Why is LiCl mixed with potassium chloride for electrolysis?
Adding KCl forms a eutectic that melts near 450 C, far below the melting point of pure LiCl, so the cell runs cooler and consumes less energy.
Q: Is lithium chloride hazardous?
It is harmful if swallowed or inhaled and irritates skin and eyes. Protective gloves, goggles and dust masks should be worn, and powder handling needs local exhaust ventilation.
Q: How should lithium chloride be stored?
Keep it in sealed moisture-barrier containers in a dry place. The salt picks up water from humid air, which changes assay, flowability and caking behaviour.