Cobalt(II) nitrate

From Crystal growing


   Cobalt(II) nitrate   
Formula: Co(NO3)2 (anhydrous)
Co(NO3)2 · 4H2O (tetrahydrate)
Co(NO3)2 · 6H2O (hexahydrate)
SMILES: [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[Co+2]
Molar mass: 182.941 g/mol (anhydrous)
255.001 g/mol (tetrahydrate)
291.030 g/mol (hexahydrate)
Density: 2.49 g/cm3 (anhydrous)
1.88 g/cm3 (hexahydrate)
Crystal system: monoclinic (hexahydrate)
a=1.42 Å, b=6.14 Å, c=12.66 Åα=90°, β=112.79°, γ=90°
monoclinic (dihydrate)
a=6.0194 Å, b=8.6294 Å, c=5.7294 Åα=90°, β=92.654°, γ=90°
hexagonal (anhydrous)
a=10.5 Å, b=10.5 Å, c=12.837 Åα=90°, β=90°, γ=120°

Color: dark-red
Melting point: 55 °C328.15 K <br />131 °F <br />590.67 °R <br /> (hexahydrate)
83.5 °C356.65 K <br />182.3 °F <br />641.97 °R <br /> (tetrahydrate)
Magnetic properties: diamagnetic
Stability: erodes (hexahydrate)
hygroscopic (anhydrous)
Hardness: fragile
Toxicity: slightly toxic


Inorganic compound, salt of transitional metal cobalt and inorganic nitric acid. From water solutions crystallizes as hexahydrate and tetrahydrate.


Reaction between cobalt(II) oxide, hydroxide or hydroxycarbonate and nitric acid

Chemical equation:

CoO + 2HNO3 = Co(NO3)2 + H2O
Co(OH)2 + 2HNO3 = Co(NO3)2 + 2H2O
Co2CO3(OH)2 + 4HNO3 = 2Co(NO3)2 + CO2↑ + 3H2O

For preparation of 100.00g of cobalt(II) nitrate hexahydrate а 25.75g of cobalt(II) oxide or 31.94g of hydroxide or 36.40g of hydroxycarbonate and 66.62g of 65% acid is required.

Add acid to the flask, then add small parts of cobalt compound with stirring until it will totally dissolve or, if you use carbonate, until carbon dioxide emission will stop. After reaction will stop, filter the solution and use it for crystal growing.

Reaction between metal cobalt and diluted nitric acid

Chemical equation:

Co + 4HNO3 = Co(NO3)2 + 2NO2↑ + 2H2O

For preparation of 100.00g of cobalt(II) nitrate hexahydrate а 20.25g of pure cobalt and 133.24g of 65% acid is required.

Add diluted acid solution to the flask, then add cobalt pieces, shavings or powder and stir it until gas emission will stop.

Reaction between cobalt(II) sulfate and calcium or lead(II) nitrate

You can use cobalt chloride instead of sulfate if you use lead salt..
Chemical equation:

CoSO4 + Ca(NO3)2 = CaSO4↓ + Co(NO3)2
CoSO4 + Pb(NO3)2 = PbSO4↓ + Co(NO3)2
CoCl2 + Pb(NO3)2 = PbCl2↓ + Co(NO3)2

For preparation of 100.00g of cobalt(II) nitrate hexahydrate а 96.59g of cobalt(II) sulfate heptahydrate or 81.75g of cobalt(II) chloride hexahydrate and 113.81g of lead(II) nitrate or 81.14g of calcium nitrate tetrahydrate is required.

Add to the flask with calcium or lead nitrate solution small parts of cobalt salt solution and stir. The large amount of poorly soluble precipitate will form. Settle it out and discard, then filter the solution carefully.

Reaction between cobalt(II) hydroxide or hydroxycarbonate and ammonium nitrate

Chemical equation:

Co(OH)2 + 2NH4NO3 = Co(NO3)2 + 2H2O + 2NH3
Co2CO3(OH)2 + 4NH4NO3 = 2Co(NO3)2 + 3H2O + 2NH3↑ + CO2

For preparation of 100.00g of cobalt(II) nitrate hexahydrate а 31.94g of cobalt(II) hydroxide or 36.40g of hydroxycarbonate and 55.01g of ammonium nitrate is required.

Add to the flask suspended in water cobalt compound and then add small parts of hot ammonium nitrate solution with heating and stirring. Emission of large amount of ammonia will begin.Attention, exuding ammonia irritates eyes and lungs! The synthesis should be carried out only in a fume hood or outdoors!

Influence of impurities

Usually does not grow as monocrystalline, a recrystallization is needed.

Storage conditions

For crystal storing use hermetic vessel with small amount of saturated solution at the bottom or place wadding moistened with such solution. You can use such alternatives as vessel with vaseline or vegetable oil, organic non-hygroscopic solvent (kerosene, benzine or paraffin). Also you can use acrylate polymer or another kinds of solidifying plastic.


Temperatureгр/100,00 гр waterгр/100,00 гр ethylene glycolгр/100,00 гр dimethylformamide
0°C273.15 K <br />32 °F <br />491.67 °R <br />84.03133.8
10°C283.15 K <br />50 °F <br />509.67 °R <br />89.6
15°C288.15 K <br />59 °F <br />518.67 °R <br />~94.3
20°C293.15 K <br />68 °F <br />527.67 °R <br />98.93400
25°C298.15 K <br />77 °F <br />536.67 °R <br />102.4320
30°C303.15 K <br />86 °F <br />545.67 °R <br />111.4
40°C313.15 K <br />104 °F <br />563.67 °R <br />125
50°C323.15 K <br />122 °F <br />581.67 °R <br />~150
60°C333.15 K <br />140 °F <br />599.67 °R <br />174
70°C343.15 K <br />158 °F <br />617.67 °R <br />184.82
80°C353.15 K <br />176 °F <br />635.67 °R <br />211
90°C363.15 K <br />194 °F <br />653.67 °R <br />338.8
Soluble in ethanol, acetone, DMSO, ethyl acetate, dioxane, tetrahydrofuran and acetonitrile.