Лития фторид

Описание

lithium fluoride is a strong irritant to the eyes and skin; potassium bromide is toxic by ingestion and inhalation; sodium chloride is table salt, a medical concern when ingested in excess, but certainly of no significant hazard to emergency responders.

Химические свойства

Lithium fluoride is a white crystalline solid. It is not hygroscopic as are the other lithium halides and is not affected by exposure to the air. Lithium fluoride is the least soluble of the alkali metal fluorides. This characteristic likens it to the alkaline earth fluorides. Lithium fluoride is different from the other lithium halides in that it does not form hydrates which can be isolated from solution. Lithium fluoride does show an increase in solubility as hydrofluoric acid is added to an aqueous solution. Under these conditions the fluoride ion is converted to the bifluoride ion, HF-2, allowing further dissolving of the solid lithium fluoride.

Физические свойства

White cubic crystals; refractive index 1.3915; density 2.635 g/cm³; melts at 845°C; vaporizes at 1,676°C; very slightly soluble in water 0.27 g/100g at 18°C; soluble in hydrofluoric acid; insoluble in alcohol.

Использование

The important uses of lithium fluoride are as flux in glasses, vitreous enamels and glazes; in soldering and welding aluminum; and its prisms in infrared spectrophotometers. The compound also is used for storing solar energy.

Подготовка

Lithium fluoride is prepared by treating an aqueous solution of lithium hydroxide or lithium carbonate with aqueous hydrofluoric acid: LiOH + HF → LiF + H2O.

Профиль безопасности

Poison by ingestion and subcutaneous routes. When heated to decomposition it emits toxic fumes of F-. Used as a flux in enamels, glasses, glazes, and weldmg. See also FLUORIDES and LITHIUM COMPOUNDS.

Методы очистки

Possible impurities are LiCO3, H2O and HF. These can be removed by calcining it at red heat, then pulverizing it with a Pt pestle and storing it in a paraffin bottle. Its solubility in H2O is 0.27% at 18o. It volatilises between 1100-1200o. [Kwasnik in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 235 1963].

Структура и конформация

The space lattice of LiF belongs to the cubic system, and its rock salt structure has a lattice constant of a=0.40173 nm and Li-F=0.201 nm. The cleavage plane is (100).