Chemical Properties
Thorium chloride is colorless or white, lustrous needles
(light-yellow color caused by iron trace); hygroscopic;
partially volatile; crystallizes with variable water of crystallization.
Deliquescent in moist air, readily
soluble in water and alcohol. Soluble in ethylenediamine.
Uses
Incandescent lighting.
Preparation
A solution of thorium hydroxide in excess hydrochloric acid
is evaporated until sirupy and is then allowed to cool and crystallize.
Further purification, in particular, removal of Fe and SiO2,
is best achieved by shaking with an ether-aqueous hydrochloric
acid mixture.
Safety Profile
Poison by intravenous
route. Moderately toxic by intraperitoneal
and subcutaneous routes. When heated to
decomposition it emits toxic fumes of Cl-.
See also THORIUM.
Purification Methods
It is freed from anionic impurities by passing a 2M solution of ThCl4 in 3M HCl through a Dowex-1 anion-resin column. The eluate is partially evaporated to give crystals which are filtered off, washed with Et2O and stored in a desiccator over H2SO4 to dry. Alternatively, a saturated solution of ThCl4 in 6M HCl is filtered through quartz wool and extracted twice with ethyl, or isopropyl ether (to remove iron), then evaporated to a small volume on a hot plate. (Excess silica precipitates and is filtered off. The filtrate is cooled to 0o and saturated with dry HCl gas.) It is shaken with an equal volume of Et2O, shaken with HCl gas, until the mixture becomes homogeneous. On standing, ThCl4.8H2O precipitates out and is filtered off, washed with Et2O and dried [Kremer J Am Chem Soc 64 1009 1942].
