Lithium Chloride
Properties
| State | Solid at room temperature |
| Color | White crystalline powder (hygroscopic) |
| Solubility | Very soluble in water (84.5 g/100 mL at 20 °C) |
| Melting Point | 605 °C |
| Boiling Point | 1382 °C |
About Lithium Chloride
Lithium chloride looks like a boring alkali halide on paper but behaves nothing like NaCl or KCl in practice. The Li+ ion has an ionic radius of just 76 pm, giving it the highest charge density of any group 1 cation, and that translates directly into LiCl's two defining quirks: extreme hygroscopicity and unusual solubility in non-aqueous solvents. A bottle of LiCl left uncapped on the bench will deliquesce into a clear syrup within hours by pulling moisture out of the air — a 30% w/w LiCl solution maintains 24% relative humidity at equilibrium, which is why LiCl brines are the working fluid in absorption-cycle dehumidifiers and HVAC desiccant wheels in commercial buildings. Unlike NaCl (insoluble in alcohols), LiCl dissolves freely in methanol, ethanol, acetone, pyridine, and even certain ethers because the small Li+ forms strong ion-dipole interactions with polar organic solvents. That property is what lets LiCl/DMAc dissolve cellulose without derivatization, the basis for the Lyocell process for making Tencel fibers. Industrially, the largest single use is as the molten-salt electrolyte (with KCl, mp 352 °C eutectic) in the Downs-style electrolysis cells that produce metallic lithium for battery anodes and aluminum-lithium aerospace alloys. Brazing fluxes for aluminum, air-conditioning desiccants, organic-synthesis additives that solubilize cellulose or modify Pd-catalyzed coupling selectivity all depend on the same small-cation chemistry.
Where you'll encounter it
If you've ever set up a humidity-controlled chamber for protein crystallography by sitting your trays over a saturated LiCl bath, or run a Mizoroki-Heck coupling with LiCl added to suppress beta-hydride elimination, you've used the lithium-cation polarizing-power tricks that make this salt useful. Crystallographers seeding 96-well sitting-drop trays exploit the LiCl saturated-salt 24% RH equilibrium to slow vapor diffusion and grow larger single crystals over days instead of hours. Pd-coupling chemists adding 1-2 equivalents of LiCl to a Heck reaction find that the chloride ligand reroutes the catalytic cycle to favor anti-Markovnikov regioselectivity by changing the active Pd species. Industrial Lyocell plants dissolving cellulose pulp in LiCl/DMAc skip the xanthate chemistry of the older viscose process entirely, which is the entire technical case for the Tencel fiber line.
Common Uses
- Molten LiCl/KCl electrolyte for electrolytic production of lithium metal
- LiCl/DMAc solvent system for cellulose dissolution (Lyocell/Tencel process)
- Saturated-salt humidity standard for calibrating hygrometers (24% RH at 20 °C)
- Desiccant brine in commercial dehumidification and absorption-cycle HVAC systems
- Brazing flux component for aluminum joining
- Additive in Pd-catalyzed Mizoroki-Heck and Stille couplings to modulate selectivity
- Source of Li+ for psychiatric research (in vitro studies; not clinical use)
- Pyrotechnic colorant producing crimson-red flame color in flares and signal fires
Safety Information
GHS: Acute Tox. 4 oral (H302), Eye Irrit. 2A (H319). Less toxic than the carbonate but still systemic — large oral doses produce the same lithium-toxicity syndrome (tremor, ataxia, renal injury) that limits psychiatric lithium dosing. OSHA does not list a specific PEL; dust handling under standard nuisance-particulate controls. Hygroscopic — store under desiccant or in a dry box. Historically used as a salt substitute in the 1940s and pulled from the market after fatal lithium intoxications in cardiac patients on low-sodium diets, an episode that ironically led to the discovery of lithium's mood-stabilizing properties.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.