Lithium Hydroxide (CAS: 1310-66-3)
Insol (in HCl)
Lithium hydroxide is an inorganic compound with the formula LiOH. It is a white hygroscopic crystalline material. It is soluble in water and slightly soluble in ethanol, and is the weakest base among the alkali metal hydroxides. It is available commercially in anhydrous form and as the monohydrate (LiOH.H2O), both of which are strong bases.
Production and reactions
Lithium hydroxide is produced in a metathesis reaction between lithium carbonate and calcium hydroxide:
Li2CO3 + Ca(OH)2 → 2 LiOH + CaCO3
The initially produced hydrate is dehydrated by heating under vacuum up to 180 °C.
In the laboratory, lithium hydroxide arises by the action of water on lithium or lithium oxide. The equations for these processes follow:
2 Li + 2 H2O → 2 LiOH + H2
Li2O + H2O → 2 LiOH
Typically, these reactions are avoided.
Although lithium carbonate is more widely used, the hydroxide is an effective precursor to lithium salts, e.g.
LiOH + HF → LiF + H2O.
Lithium hydroxide is mainly consumed for the production of lithium greases. A popular lithium grease is lithium stearate, which is a general-purpose lubricating grease due to its high resistance to water and usefulness at both high and low temperatures.
Carbon dioxide scrubbing
Further information: carbon dioxide scrubber
Lithium hydroxide is used in breathing gas purification systems for spacecraft, submarines, and rebreathers to removecarbon dioxide from exhaled gas by producing lithium carbonate and water:
2 LiOH·H2O + CO2 → Li2CO3 + 3 H2O
2LiOH + CO2 → Li2CO3 + H2O
The latter, anhydrous hydroxide, is preferred for its lower mass and lesser water production for respirator systems in spacecraft. One gram of anhydrous lithium hydroxide can remove 450 cm3 of carbon dioxide gas. The monohydrate loses its water at 100–110 °C.
It is used as a heat transfer medium and as a storage-battery electrolyte. It is also used in ceramics and some Portland cement formulations. Lithium hydroxide (isotopically enriched in lithium-7) is used to alkalize the reactor coolant inpressurized water reactors for corrosion control.