Rhodium(III) oxide

Dirhodiumtrioxid

Gray-black odorless solid

Fixed

8.20 g · cm -3

1100 ° C ( decomposition)

Insoluble in water

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Rhodium ( III) oxide is an inorganic chemical compound of the rhodium from the group of oxides.

Production and representation

Rhodium ( III) oxide can be prepared by reacting anhydrous rhodium (III ) salts such as rhodium (III ) chloride are obtained with oxygen at 750-800 ° C. It can also be obtained directly from the elements. The rhodium (III ) oxide hydrate can be obtained by precipitation of aqueous sodium hexachlororhodate or potassium hexachlororhodate solution with sodium or potassium hydroxide solution.

Properties

Rhodium ( III ) oxide is a paramagnetic black gray odorless solid that is soluble neither in water nor in acids. It has a crystal structure isotypic with that of aluminum (III ) oxide ( corundum) with the space group R3c (A = 547 pm, α = 55 ° 40 '). At 750 ° C, this turns into an orthorhombic form. His pentahydrate ( Rhodiumoxidhydrat ) is a pale yellow powder, which is insoluble and soluble in acids in water. By reaction with nitric acid, leads to the rhodium ( III) nitrate.