Iron(III) oxide-hydroxide
- Iron (III ) oxide hydrate
- Iron hydroxide
- 20344-49-4
- 51274-00-1 ( Eisenhydroxidoxidgelb )
- 1310-14-1 ( goethite )
Yellow odorless powder
Fixed
3.4 to 3.9 g · cm -3
> 1000 ° C.
Sparingly soluble in water
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Iron (III) oxide hydroxide is an inorganic chemical compound having the composition FeO (OH). This can also be written as Fe2O3, H2O at the same ratio of elements; so it belongs to the group of iron hydroxides or iron ( III) oxide hydrates, which differ in their degree of hydration.
Occurrence
α - iron ( III) oxide hydroxide occurs in nature as limonite or goethite. The y- form is found in nature as ruby mica or lepidocrocite.
Production and representation
α - iron ( III) oxide hydroxide is a rust-colored, voluminous precipitate (III ) nitrate as iron () with hydroxide precipitates of iron (III ) salt solutions when moving.
γ -iron (III ) oxide hydroxide is obtained by reaction of iron (II ) chloride tetrahydrate with hexamethylene tetramine and reaction of the intermediate product iron ( II) hydroxide with a sodium nitrite solution.
Properties
The precipitate dissolves readily in acids, is in a basic medium but practically insoluble. This is exploited, for example, from the cation separation process for the separation of iron.
Only with hot concentrated bases can be prepared Hydroxoferrate (III). When heating is iron ( III) oxide hydroxide in α -Fe2O3.
α - iron ( III) oxide hydroxide has an orthorhombic crystal structure, isotypic to that of diaspore (space group Pbnm, a = 464 pm, b = 1000 pm, c = 303 pm ).
γ - iron ( III) oxide hydroxide is composed of extremely fine needles, slightly stäubendes powder of deep orange-red color. It can be conducted by heating in a vacuum or dry air stream in the range of about 250 to 400 ° C in a pure y -Fe2O3. At higher heating or even very intense attrition arises from the metastable preparations of γ - series of metastable β - FeO ( OH), the stable α - modification. The γ - modification has an orthorhombic crystal structure (space group BBMM, a = 1,240 pm, 387 pm b = c = 306 pm ).