Cobalt(II) chloride

Cobalt(II) chloride, also known as cobaltous chloride and cobalt dichloride, is a chemical compound. It contains cobalt in its +2 oxidation state. Its chemical formula is CoCl₂. It contains cobalt and chloride ions.

Cobalt(II) chloride

Anhydrous Hexahydrate
Structure of anhydrous compound
Structure of hexahydrate
Names
IUPAC name Cobalt(II) chloride
Other names Cobaltous chloride Cobalt dichloride Muriate of cobalt[1]
Identifiers
CAS Number	7646-79-9 Y 16544-92-6 (dihydrate) N 7791-13-1 (hexahydrate) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:35696 Y
ChemSpider	22708 Y
ECHA InfoCard	100.028.718
EC Number	231-589-4
PubChem CID	3032536
RTECS number	GF9800000
UNII	EVS87XF13W Y 17AVG63ZBC (hexahydrate) Y
UN number	3288
CompTox Dashboard (EPA)	DTXSID9040180
SMILES Cl[Co]Cl
Properties
Chemical formula	CoCl2
Molar mass	129.839 g/mol (anhydrous) 165.87 g/mol (dihydrate) 237.93 g/mol (hexahydrate)
Appearance	blue crystals (anhydrous) violet-blue (dihydrate) rose red crystals (hexahydrate)
Density	3.356 g/cm3 (anhydrous) 2.477 g/cm3 (dihydrate) 1.924 g/cm3 (hexahydrate)
Melting point	726 °C (1,339 °F; 999 K) ±2 (anhydrous) 140 °C (monohydrate) 100 °C (dihydrate) 86 °C (hexahydrate)
Boiling point	1,049 °C (1,920 °F; 1,322 K)
Solubility in water	43.6 g/100 mL (0 °C) 45 g/100 mL (7 °C) 52.9 g/100 mL (20 °C) 105 g/100 mL (96 °C)
Solubility	38.5 g/100 mL (methanol) 8.6 g/100 mL (acetone) soluble in ethanol, pyridine, glycerol
Magnetic susceptibility (χ)	+12,660·10−6 cm3/mol
Structure
Crystal structure	CdCl2 structure
Coordination geometry	hexagonal (anhydrous) monoclinic (dihydrate) Octahedral (hexahydrate)
Hazards
NFPA 704	0 3 0
Flash point	Non-flammable
Related compounds
Other anions	{{{value}}}
Other cations	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Cobalt(II) chloride hexahydrate (with six water molecules attached)

Cobalt(II) chloride anhydrous (with no water molecules attached)

Properties

Cobalt(II) chloride is normally found in the red (or pink) form. The red form has water in it. It can be heated to turn it into the blue form, without water. The blue form will absorb water from the air and turn red again.

Cobalt(II) chloride reacted with hydrochloric acid. The pink form is just cobalt chloride. The blue form is the color that it gives with some hydrochloric acid. The green form is cobalt chloride reacted with a lot of hydrochloric acid.

A different blue form is made when cobalt(II) chloride is reacted with a chemical compound that has chloride in it. Hydrochloric acid works the best, but sodium chloride can be used too. When it is heated, it turns more blue than when it is cooled.

Unheated picture

The heated picture

for an example. Cobalt chloride can be used to test for chloride ions in this way.

It can be oxidized to cobalt(III) compounds, although cobalt(III) chloride does not exist. If it is made, it just drops a Cl from CoCl₃, making CoCl₂ (cobalt(II) chloride) again.

Preparation

The anhydrous (without water) blue form can be made by reacting cobalt with chlorine. The hydrated (with water) red form can be made by reacting cobalt(II) oxide or cobalt(II) hydroxide with hydrochloric acid.

Uses

It is used to place cobalt into other chemical compounds. It can be used to make other cobalt compounds. It is the most common cobalt compound in the lab.

Safety

It is a weak oxidizing agent, too weak to ignite things. Cobalt compounds are toxic in large quantities, like any other transition metal compounds. They are not toxic like lead or mercury compounds, though.