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2 O 3 has the corundum structure, consisting of a hexagonal close packed array of oxide anions with 2 ⁄ 3 of the octahedral holes occupied by chromium. Similar to corundum, Cr 2 O 3 is a hard, brittle material (Mohs hardness 8 to 8.5). [3] It is antiferromagnetic up to 307 K, the Néel temperature. [4] [5] It is not readily attacked by acids.
The chromium is oxidized to the hexavalent form, while the iron forms iron(III) oxide, Fe 2 O 3: 4 FeCr 2 O 4 + 8 Na 2 CO 3 + 7 O 2 → 8 Na 2 CrO 4 + 2 Fe 2 O 3 + 8 CO 2. Subsequent leaching of this material at higher temperatures dissolves the chromates, leaving a residue of insoluble iron oxide. Normally the chromate solution is further ...
Phenylpropanoic acid or hydrocinnamic acid is a carboxylic acid with the formula C 9 H 10 O 2 belonging to the class of phenylpropanoids. It is a white, crystalline solid with a sweet, floral scent at room temperature. Phenylpropanoic acid has a wide variety of uses including cosmetics, food additives, and pharmaceuticals. [5]
Lead(II) chromate can be produced by treating sodium chromate with lead salts such as lead(II) nitrate or by combining lead(II) oxide with chromic acid.. Related lead sulfochromate pigments are produced by the replacement of some chromate by sulfate, resulting in a mixed lead-chromate-sulfate compositions Pb(CrO 4) 1−x (SO 4) x.
The latter route requires aluminium trichloride as a catalyst. [3] The bromochloromethane product from either reaction can further react in a similar manner: 6 CH 2 BrCl + 3 Br 2 + 2 Al → 6 CH 2 Br 2 + 2 AlCl 3 CH 2 BrCl + HBr → CH 2 Br 2 + HCl. In the laboratory, it is prepared from bromoform using sodium arsenite and sodium hydroxide: [4 ...
Other compounds with the general formula Cr(ClO 4) 3 (NH 3) x are also known. When x = 3, this compound is red, when x = 4 or 5, it is orange. [5] The hexammine complex will explode. [5] Cr(ClO 4) 3 can also form complexes with N 2 H 4, such as purple Cr(ClO 4) 3 ·2N 2 H 4. [6] Cr(ClO 4) 3 can also form complexes with urea (CO(NH 2) 2), such ...
It can be prepared by reduction of chromium(III) bromide with hydrogen gas for 6–10 hours at 350-400 °C, cogenerating hydrogen bromide: [2] 2 CrBr 3 + H 2 → 2 CrBr 2 + 2 HBr. Treatment of chromium powder with concentrated hydrobromic acid gives a blue hydrated chromium(II) bromide, which can be converted to a related acetonitrile complex. [3]
The relatively complicated formula - [Cr(H 2 O) 6](NO 3) 3 •3H 2 O - betray a simple structure of this material. The chromium centers are bound to six aquo ligands , and the remaining volume of the solid is occupied by three nitrate anions and three molecules of water of crystallization .