Chemical Properties
Heavy white powder. Mohs hardness
6.5, very refractory. Soluble in sulfuric acid; insoluble
in water.
Uses
Ceramics (high temperature), gas mantles,
nuclear fuel, flame spraying, crucibles, medicine,
nonsilica optical glass, catalyst, thoriated tungsten
filaments.
General Description
White powder. Density 9.7 g / cm3. Not soluble in water. Used in high-temperature ceramics, gas mantles, nuclear fuel, flame spraying, crucibles, non-silicia optical glass, catalysis, filaments in incandescent lamps, cathodes in electron tubes and arc-melting electrodes.
Air & Water Reactions
Insoluble in water.
Reactivity Profile
Has only weak oxidizing powers. Redox reactions can however still occur. Not water-reactive. Soluble in sulfuric acid.
Physical properties
White cubic crystals; refractive index 2.200 (thorianite); density 10.0 g/cm3; hardness 6.5 Mohs; melts at 3,390°C; vaporizes at 4,400°C; insoluble in water or alkalis; soluble in acids with difficulties.
Definition
A white insoluble compound, used
as a refractory, in gas mantles, and as a replacement for silica in some types of optical glass.
Preparation
Thorium dioxide is obtained as an intermediate in the production of thorium metal from monazite sand (See Thorium).
The compound also can be prepared by many other methods including thermal decomposition of thorium oxalate, hydroxide, carbonate, or nitrate. Heating thorium metal in oxygen or air, and hydrolysis of thorium halides also yield thorium dioxide.
Industrial uses
Thoria, the most chemically stable oxideceramic, is only attacked by some earth alkalimetals under some conditions. It has the highestmelting point (3315°C) of the oxide ceramics.Like beryllia, it is costly. Also, it has highthermal expansion and poor thermal shockresistance.
Carcinogenicity
Thorium dioxide is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans.
