Chromium trioxide
Chromic anhydride, chromium trioxide
Dark red, odorless crystalline needles
Fixed
2.7 g · cm -3 ( 20 ° C)
197 ° C
Decomposing above 230 ° C.
Very well in water (1854 g · l-1 at 20 ° C)
Risk
Repealed as carcinogenic
- 50 mg · kg -1 ( LD50, rat, oral)
- 0.217 mg · l-1 · 4 h ( LC50, rat, inh. )
- 55 mg · kg -1 ( LD50, rat, transdermal)
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Chromium (VI ) oxide, and chromium trioxide ( CrO3 ) is an oxide of chromium. It is a dark red solid, which is hygroscopic and readily soluble in water. The aqueous solution is strongly acidic ( chromic acid ). From the fabric to go from a number of hazards.
Properties
Chromium ( VI) oxide is red-violet, odorless, needle-shaped crystals. In much water it dissolves with the formation of yellow chrome acid ( H2CrO4 ). Add a little water also form condensed chromic acids. During annealing of chromium ( VI) oxide, it is decomposed to form chromium ( III) oxide and oxygen:
Chromium ( VI) oxide is an excellent oxidizing agent, which reacts explosively such as with ethanol or other organic substances.
The crystal lattice of chromium ( VI) oxide consists of chains of corner-sharing tetrahedra, which are significantly distorted in the chain direction
Synthesis / presentation
Chromium (VI ) oxide is prepared by precipitation of a chromate concentration with concentrated sulfuric acid.
Use
In electroplating, in wood preservatives, for the preparation of chromium ( IV) oxide, potassium dichromate, and ammonium dichromate, as a strong oxidant ( Jones oxidation ).
Safety
Chromium ( VI) oxide is oxidizing and increases the risk of fire when in contact with combustible materials. When mixed with combustible substances cause an explosion. Chromium ( VI) oxide is highly toxic and affects both mutagenic and carcinogenic. Already 0.6 g, taken orally, can be fatal. In case of ingestion are digestive disorders, kidney damage, convulsions and paralysis result. Aqueous solutions of chromium ( VI) oxide are highly corrosive. Also, the solid leads in contact with skin and mucous membranes to severe burns. Chromium ( VI) oxide is environmentally hazardous and extremely hazardous for water (water hazard class 3).