Iron(III)-ammonium sulfate

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Crystal compoundsSaltsSulfatesIron(III)-ammonium sulfate


  Iron(III)-ammonium sulfate   
Names: ammonium-iron(III) sulfate
monoammonium-iron(III) sulfate
ferric-ammonium sulfate
iron-ammonium alum
iron alum

Formula: NH4Fe(SO4)2 (anhydrous)
NH4Fe(SO4)2 · 12H2O (dodecahydrate)
SMILES: [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Fe+3].[NH4+]
Molar mass: 266.006 g/mol (anhydrous)
482.184 g/mol (dodecahydrate)
Density: 1.71 g/cm3 (dodecahydrate)
Crystal system: monoclinic (trihydrate)
a=9.982 Å
9.9820 Å
0.9982 nm
, b=10.156 Å
10.1560 Å
1.0156 nm
, c=9.504 Å
9.5040 Å
0.9504 nm
α=90°
90°  
, β=94.95°
94°57′  
, γ=90°
90°  

cubic (dodecahydrate)
a=12.293 Å
12.2930 Å
1.2293 nm
, b=12.293 Å
12.2930 Å
1.2293 nm
, c=12.293 Å
12.2930 Å
1.2293 nm
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

Shapes:
https://media.crystalls.info/w/uploads/media/Octahedron.json
https://media.crystalls.info/w/uploads/media/Tetragonal_pyramid.json
https://media.crystalls.info/w/uploads/media/Truncated_octahedron.json

Template:Cubeоoctahedron

Color: light-violet
pale-violet
light-purple
purple
Melting point: 39 °C
312.15 K
102.2 °F
561.87 °R
(dodecahydrate)
Decomposition point: 230 °C
503.15 K
446 °F
905.67 °R
(anhydrous)
Refractive index: 1.4854 (dodecahydrate)
Stability: erodes (dodecahydrate)
hygroscopic (anhydrous)
Hardness: strong
Toxicity: slightly toxic

Description

Inorganic compound, double salt of transitional metal iron, ammonium ion and inorganic sulfuric acid. From water solutions crystallizes as dodecahydrate.

Precursors

Reaction between pure iron, ammonium nitrate and sulfuric acid

Chemical equation:

2H2SO4 + NH4NO3 + Fe = NH4Fe(SO4)2 + NO↑ + 2H2O

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 11.58g of iron, 16.60g of ammonium nitrate and 109.95g of 37% sulfuric acid is required.
Add acid to the flask, then add small parts of iron compound with stirring until it will totally dissolve . After reaction will stop, filter the solution and use it for crystal growing.

Reaction between iron and ammonium sulfates

Chemical equation:

(NH4)2SO4 + Fe2(SO4)3 = 2NH4Fe(SO4)2

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 63.88g of iron(III) sulfate dodecahydrate and 13.70g of ammonium sulfate is required.
Dissolve compounds in hot water apart and then mix solutions into one container with intense stirring. Cooling or evaporation of a solution will cause double salt crystallyzation.

Reaction between Mohr's salt and hydrogen peroxide in sulfuric acid solution

Chemical equation:

2(NH4)2Fe(SO4)2 + H2O2 + H2SO4 = 2NH4Fe(SO4)2 + (NH4)2SO4 + 2H2O

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 81.32g of mohr's salt hexahydrate, 11.76g of 30% hydrogen peroxide and 27.49g of 37% sulfuric acid is required.
Add to the flask with sulfuric acid solution hydrogen peroxide and then add small parts of {{{reducing_agent}}} with stirring until oxide emission will stop.

Reaction between iron(III) nitrate or chloride and ammonium sulfate

Chemical equation:

2(NH4)2SO4 + Fe(NO3)3 = NH4Fe(SO4)2 + 3NH4NO3
2(NH4)2SO4 + FeCl3 = NH4Fe(SO4)2 + 3NH4Cl

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 83.78g of iron(III) nitrate nonahydrate or 56.06g of iron(III) chloride hexahydrate and 54.81g of ammonium sulfate is required.
Dissolve compounds in hot water apart and then mix solutions into one container with intense stirring. Cooling or evaporation of a solution will cause double salt crystallyzation. Filter precipitate and wash it wish small amount of ethanol, then filter the solution and use it for crystal growing.

Reaction between iron(III) sulfate and nitrate or ammonium chloride

Chemical equation:

3NH4NO3 + 2Fe2(SO4)3 = 3NH4Fe(SO4)2 + Fe(NO3)3
3NH4Cl + 2Fe2(SO4)3 = 3NH4Fe(SO4)2 + FeCl3

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 85.18g of iron(III) sulfate dodecahydrate and 16.60g of ammonium nitrate or 11.09g of ammonium chloride is required.
Dissolve compounds in hot water apart and then mix solutions into one container with intense stirring. Cooling or evaporation of a solution will cause double salt crystallyzation. Filter precipitate and wash it wish small amount of ethanol, then filter the solution and use it for crystal growing.

Reaction between ammonium hydroxide, iron(III) hydroxide and sulfuric acid

Chemical equation:

2H2SO4 + NH4OH + Fe(OH)3 = NH4Fe(SO4)2 + 4H2O

For preparation of 100.00g of iron(III)-ammonium sulfate dodecahydrate а 7.27g of ammonium hydroxide, 22.16g of iron(III) hydroxide and 109.95g of 37% sulfuric acid is required.
Add acid to the flask, then add small parts of ammonium and iron 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.

Influence of impurities

Addition of borax has no affect on crystal shape, as it does with ammonium alum.

Notes

Unlike chrome-potassium or chrome-ammonium alums, coating with a layer of other alum (for protection against erosion) is difficult - due to high solubility, placing a iron alum crystal to solution of other alums leads to crystal dissolving.

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

Temperatureгр/100,00 гр water
25°C
298.15 K
77 °F
536.67 °R
124
124 g/100g
55.357 %
100°C
373.15 K
212 °F
671.67 °R
400
400 g/100g
80 %
Insoluble in ethanol and acetone.

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