COBALT(II) IODIDE Property

Melting point:

>515 °C(lit.)

Boiling point:

570°C

Density 

5.45 g/mL at 25 °C(lit.)

Flash point:

570°C vac.

solubility 

acetone: slightly soluble(lit.)

form 

powder

color 

White

Specific Gravity

5.68

Water Solubility 

Soluble in water.

Sensitive 

Hygroscopic

Merck 

14,2443

Exposure limits

ACGIH: TWA 0.02 mg/m3

Stability:

hygroscopic

CAS DataBase Reference

15238-00-3(CAS DataBase Reference)

EPA Substance Registry System

Cobalt iodide (CoI2) (15238-00-3)

Safety

Hazard Codes 

Xn

Risk Statements 

20/21/22-36/37/38

Safety Statements 

26-36

WGK Germany 

3

TSCA 

Yes

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Warning

Hazard statements

H315Causes skin irritation

H317May cause an allergic skin reaction

H319Causes serious eye irritation

H335May cause respiratory irritation

H341Suspected of causing genetic defects

Precautionary statements

P201Obtain special instructions before use.

P261Avoid breathing dust/fume/gas/mist/vapours/spray.

P280Wear protective gloves/protective clothing/eye protection/face protection.

P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.

P308+P313IF exposed or concerned: Get medical advice/attention.

P405Store locked up.

COBALT(II) IODIDE Chemical Properties,Usage,Production

Description

Cobalt iodide appears as black crystals with a slight ‘iodine’-like odour. When heated to decomposition, it may emit toxic fumes of iodine and oxides of nitrogen. Anhydrous cobalt (II) iodide is sometimes used to test for the presence of water in various solvents. Cobalt (II) iodide is used as a catalyst, for example, in carbonylations. It catalyses the reaction of diketene with Grignard reagents, useful for the synthesis of terpenoids.

Chemical Properties

Brownish red crystalline powder

Physical properties

Exists in two isomorphous forms, α- and ?-forms; both modifications highly hygroscopic. The α-form is black hexagonal crystal; density 5.58 g/cm³; turns dark green in air; melts at 560°C; disolves in water giving pink coloration. The α-forms sublimes in vacuo, partly forming an isomorous yellow modification-the anhydrous β-form.
The β-modification is a yellow powder; density 5.45 g/cm³; converts to the α-form when heated to 400°C; absorbs moisture from air, the yellow powder becoming green droplets; dissolves readily in water forming a colorless solution which turns pink on heating.
The hexahydrate is red hexagonal crystals; density 2.90 g/cm³; loses water at 130°C giving anhydrous iodide; soluble in water, ethanol, acetone, chloroform and ether, forming colored solutions, (while the aqueous solution is red below 20°C and green above this temperature; the salt forms blue solution in ethanol, chloroform and ether).

Uses

Cobalt(II) iodide is used as a moisture and humidity indicator. It is also used as a catalyst.

Uses

Hygrometers; determination of water in organic solvents; catalyst.

Preparation

Cobalt(II) iodide is prepared by heating cobalt powder in a stream of hydrogen iodide at 400 to 450°C:
Co + 2HI → CoI₂ + H₂
The product obtained is the black crystalline α-form.
Cobalt(II) iodide also may be made by heating cobalt powder with iodine vapor.

Structure and conformation

Cobalt(II) iodide crystallizes in two polymorphs, the α- and β-forms. The α-polymorph comprises black hexagonal crystals, which turn dark green when exposed to air. Under vacuum at 500℃, samples of α-CoI2 sublime, forming the β-polymorph as yellow crystals. β-CoI2 also easily absorbs moisture from the air, converting into green hydrate. Below 400℃, β-CoI2 reverts back to the α-form. The anhydrous salt has the cadmium halide structure. The hexaaquo salt comprises separated [Co(H2O)6] 21 and iodide ions.