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Cobalt(III)-ammonium sulfate | |
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Names: | ammonium-cobalt(III) sulfate cobalt-ammonium alum cobaltic alum |
Formula: | NH4Co(SO4)2 (anhydrous) NH4Co(SO4)2 · 12H2O (dodecahydrate) |
Molar mass: | 269.094 g/mol (anhydrous) 485.272 g/mol (dodecahydrate) |
Crystal system: | cubic (dodecahydrate) α=90°, β=90°, γ=90° |
Shapes: | |
Color: | dark-blue |
Stability: | decomposes (dodecahydrate) |
Hardness: | strong |
Toxicity: | moderately toxic |
Description
Inorganic compound, double salt of transitional metal cobalt, ammonium ion and inorganic sulfuric acid. Unlike complexed ions, aqueous cobalt(III) ion is extremely oxidizing and can oxidize water quickly, so cold sulfuric acid of at least 5mol/L is needed to handle it. From water solutions crystallizes as dodecahydrate.
Precursors
Reaction between sodium tris(carbonato)cobaltate(III), sulfuric acid and ammonium sulfate
Chemical equation:
100.00
g of cobalt(III)-ammonium sulfate dodecahydrate
а 63.45
g of sodium tris(carbonato)cobalt(iii) and 13.61
g of ammonium sulfate is required.
Add the carbonato complex carefully into cold sulfuric acid, then add cold sulfuric acid solution of ammonium sulfate and cool this solution down to crystallize the alum.
Electrolysis of solution of cobalt(II) sulfate in sulfuric acid then add ammonium sulfate
Chemical equation:
100.00
g of cobalt(III)-ammonium sulfate dodecahydrate
а 31.94
g of cobalt(ii) sulfate and 13.61
g of ammonium sulfate is required.
Electrolyze cold solution with a Pt or PbO2 anode and a cathode in separated cell, until solution becomes blue, then add cold sulfuric acid solution of ammonium sulfate and cool this solution down to crystallize the alum. If you want mixed crystals with ammonium alum, you can simply electrolyze a solution saturated with ammonium alum containing cobalt(ii) sulfate at room temperature without partitioning, until solution becomes brown, and freeze it to crystallize.
Notes
Pure compound is very unstable at room temperature, but mixed crystals with ammonium alum are quite stable.
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.
Solubility
Gallery
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Ammonium alum crystals covered with a thin layer of mixed NH4-Al and NH4-Co alum.Cobalt(III)-ammonium sulfate, Vicky Silviana, twitterTwitter
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Small crystals of mixed NH4-Al and NH4-Co alum.Cobalt(III)-ammonium sulfate, Vicky Silviana, twitterTwitter
Sources
Cobalt compounds | |
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Salts |
Cobalt(II) chloride (CoCl2) • Cobalt(II) nitrate (Co(NO3)2) • Cobalt(II) oxalate (CoC2O4) • Cobalt(II) sulfate (CoSO4) • Cobalt(II) tartrate (CoC4H4O6) |
Double salts |
Cerium(III)-cobalt nitrate (3Co(NO3)2 · 2Ce(NO3)3) • Cerium(III)-cobalt-manganese nitrate (3(Co,Mn)(NO3)2 · 2Ce(NO3)3) • Cobalt(II)-ammonium sulfate ((NH4)2Co(SO4)2) • Cobalt(III)-ammonium sulfate (NH4Co(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) |
Complexes |
Cyanocobalamin (C63H88CoN14O14P) • Hexamminecobalt(III) chloride ([Co(NH3)6]Cl2) • Hexanitrocobaltates • Hexacyanocobaltates • Trioxalatocobaltates |