Cobalt (II, III) oxide

Crystal structure
__ Co 3+      __ Co 2+      __ O 2−
General
Surname	Cobalt (II, III) oxide
other names	Tricobalt tetraoxide
Ratio formula	Co 3 O 4
Brief description	black odorless solid
External identifiers / databases
CAS number 1308-06-1 EC number 215-157-2 ECHA InfoCard 100.013.780 PubChem 11651651 ChemSpider 9826389 Wikidata Q419886
properties
Molar mass	240.8 g mol −1
Physical state	firmly
density	6.11 g cm −3 (20 ° C)
Melting point	> 900 ° C (decomposition)
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 334-412 P: 261-273-284-304 + 340-342 + 311
Toxicological data	> 5000 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cobalt (II, III) oxide is a chemical compound of cobalt and oxygen . The black solid is one of several oxides of cobalt and belongs to the group of spinels .

Extraction and presentation

Cobalt (II, III) oxide is formed when cobalt (II) oxide is heated in air to 400 to 500 ° C.

${\displaystyle \mathrm {6\ CoO+O_{2}\longrightarrow 2\ Co_{3}O_{4}} }$

properties

Cobalt (II, III) oxide is a mixed-valent compound with divalent and trivalent cobalt ions and the more precise formula Co ²⁺ Co ³⁺ ₂ O ₄ (CoO · Co ₂ O ₃ ). The compound has a spinel structure in which one eighth of all tetrahedral gaps and half of the octahedral gaps are occupied by cobalt ions in a cubic closest packing of spheres by O ²⁻ ions . The Co ²⁺ ions occupy the tetrahedral gaps, the Co ³⁺ ions the octahedral gaps. The crystals have the space group Fd 3 m (space group no. 227) , the lattice parameter a = 809 pm. In the unit cell there are eight formula units .

From around 900 ° C cobalt (II, III) oxide decomposes to cobalt (II) oxide. The compound is reduced to elemental cobalt by reducing agents such as coke or aluminum .

Cobalt (II, III) oxide is insoluble in hydrochloric acid , nitric acid and aqua regia , but soluble in concentrated sulfuric acid and in molten potassium hydrogen sulfate .

use

Cobalt (II, III) oxide is an important intermediate product in the production of metallic cobalt. By roasting and leaching , cobalt (II, III) oxide is first obtained from various cobalt ores (mostly sulfides or arsenides ). This can now be reduced to the element with carbon or aluminothermically .

Cobalt (II, III) oxide can be used as a catalyst for the oxidation of ammonia to nitric acid. This is significantly cheaper than the platinum alloys otherwise used . One disadvantage, however, is the hitherto lower selectivity of cobalt (II, III) oxide catalysts.

Like other cobalt compounds, cobalt (II, III) oxide is a blue pigment for coloring ceramics.

safety instructions

Cobalt (II, III) oxide is considered to be carcinogenic and germ cell mutagenic .

Individual evidence

1. ↑ ^{a b c d e f g h i} Entry on cobalt (II, III) oxide in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
2. ^ ^{A b c d} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , pp. 1682-1687.
3. ^ ^{A b} Jean D'Ans, Ellen Lax: Paperback for chemists and physicists. 3. Elements, inorganic compounds and materials, minerals, Volume 3. 4. Edition, Springer, 1997, ISBN 978-3-540-60035-0 , p. 388 ( limited preview in Google book search).
4. ↑ Poul Erik Højlund Nielsen, Keld Johansen: Ammonia oxidation Catalyst . EP19930104797 , 1993.
5. ^ Fa. Lehrer: Raw material overview ceramics ( Memento of January 8, 2004 in the Internet Archive )