Литий йодид

Химические свойства

White to off-white crystalline powder

Физические свойства

White cubic crystals; refractive index 1.955; density 4.076 g/cm³; melts at 449°C; vaporizes around 1,180°C; highly soluble in water (165 g/100g at 20°C), solubility greatly increases in hot water (433g/100g at 80°C); also very soluble in methanol (343 g/100g at 20°C) and ammonia; soluble in acetone (42.6g/100g at 18°C).
The trihydrate, LiI?3H₂O, is a yellowish solid (due to the release of iodine when exposed to air); hexagonal crystals; hygroscopic; density 3.48 g/cm³; loses iodine when heated in air; loses one molecule of water of crystallization at 73°C becoming dihydrate, LiI?2H₂O and loses the second molecule at 80°C, forming monohydrate, LiI?H₂O and becomes anhydrous at 130°C; highly soluble in water; soluble in ethanol and acetone.

Использование

It is used as a absorbent in refrigeration process, as a catalyst, and in photography. It is also useful for organic synthesis, pessat iodination, cleavage of esters, ethers, epoxides, decarboethoxylation, carbonylation, and aldol condensation. It is used for manufacturing medicines and mineral waters. It is used in electochemicstry and redox reactions. Lithium iodide is also a catalyzed conjugate addition reaction of β-dicarbonyl compounds. It is also useful for tetrathioquinodimethane.

Подготовка

The trihydrate salt is obtained by neutralization of lithium hydroxide or lithium carbonate solution with pure hydriodic acid followed by concentration of the solution for crystallization:
LiOH + HI → LiI + H₂O
When heated in a vacuum, the trihydrate dehydrates to anhydrous salt.

Методы очистки

Crystallise it from hot water (0.5mL/g) by cooling in a CaCl2-ice EtOH or from an acetone-Dry-Ice bath. Dry it under a vacuum over P2O5 for 1hour at 60o and then at 120o. It is deliquescent and should be stored in a tightly stoppered vessel in the dark.