Aluminum-ammonium sulfate

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Crystal compoundsSaltsSulfatesAluminum-ammonium sulfate


  Aluminum-ammonium sulfate   
Names: aluminum(III)-ammonium sulfate
ammonium-aluminum sulfate
ammonium alum

Formula: NH4Al(SO4)2 (anhydrous)
NH4Al(SO4)2 · 12H2O (dodecahydrate)
SMILES: [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Al+3].[NH4+]
Molar mass: 237.143 g/mol (anhydrous)
453.321 g/mol (dodecahydrate)
Density: 2.45 g/cm3 (anhydrous)
1.645 g/cm3 (dodecahydrate)
Crystal system: hexagonal (anhydrous)
a=4.724 Å
4.7240 Å
0.4724 nm
, b=4.724 Å
4.7240 Å
0.4724 nm
, c=8.225 Å
8.2250 Å
0.8225 nm
α=90°
90°  
, β=90°
90°  
, γ=120°
120°  

cubic (dodecahydrate)
a=12.248 Å
12.2480 Å
1.2248 nm
, b=12.248 Å
12.2480 Å
1.2248 nm
, c=12.248 Å
12.2480 Å
1.2248 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
https://media.crystalls.info/w/uploads/media/Cuboctahedron.json
https://media.crystalls.info/w/uploads/media/Cube.json

Color: colorless
white
Melting point: 93.5 °C
366.65 K
200.3 °F
659.97 °R
(dodecahydrate)
Boiling point: 120 °C
393.15 K
248 °F
707.67 °R
(dodecahydrate)
Refractive index: 1.572 (anhydrous)
1.459 (dodecahydrate)
Stability: stable (dodecahydrate)
hygroscopic (anhydrous)
Hardness: fragile
(1.5 on Moh`s scale)
Toxicity: non-toxic

Description

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

Minerals

Occurs in nature as tschermigite and godovikovite minerals.

Precursors

Reaction between aluminum and ammonium sulfates

Chemical equation:

(NH4)2SO4 + Al2(SO4)3 = 2NH4Al(SO4)2

For preparation of 100.00g of aluminum-ammonium sulfate dodecahydrate а 73.50g of aluminum sulfate octadecahydrate and 14.57g 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 pure aluminum, ammonium nitrate and sulfuric acid

Chemical equation:

2H2SO4 + NH4NO3 + Al = NH4Al(SO4)2 + NO↑ + 2H2O

For preparation of 100.00g of aluminum-ammonium sulfate dodecahydrate а 5.95g of aluminum, 17.66g of ammonium nitrate and 116.95g of 37% sulfuric acid is required.
Add acid to the flask, then add small parts of aluminum compound with stirring until it will totally dissolve . After reaction will stop, filter the solution and use it for crystal growing.

Reaction between aluminum nitrate or chloride and ammonium sulfate

Chemical equation:

2(NH4)2SO4 + Al(NO3)3 = NH4Al(SO4)2 + 3NH4NO3
2(NH4)2SO4 + AlCl3 = NH4Al(SO4)2 + 3NH4Cl

For preparation of 100.00g of aluminum-ammonium sulfate dodecahydrate а 82.75g of aluminum nitrate nonahydrate or 53.26g of aluminum chloride hexahydrate and 58.30g 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 aluminum sulfate and nitrate or ammonium chloride

Chemical equation:

3NH4NO3 + 2Al2(SO4)3 = 3NH4Al(SO4)2 + Al(NO3)3
3NH4Cl + 2Al2(SO4)3 = 3NH4Al(SO4)2 + AlCl3

For preparation of 100.00g of aluminum-ammonium sulfate dodecahydrate а 98.00g of aluminum sulfate octadecahydrate and 17.66g of ammonium nitrate or 11.80g 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 ammonia, aluminum hydroxide and sulfuric acid

Chemical equation:

2H2SO4 + NH4OH + Al(OH)3 = NH4Al(SO4)2 + 4H2O

For preparation of 100.00g of aluminum-ammonium sulfate dodecahydrate а 30.92g of 25% ammonia, 17.21g of aluminum hydroxide and 116.95g of 37% sulfuric acid is required.
Add acid to the flask, then add small parts of ammonium and aluminum 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 affects on crystals shape - small amounts of this compound lead to beveling of crystal corners, then large amounts lead to changing crystal shape to cuboctahedron or even cube. A similar effect has some organic dyes.

Storage conditions

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

Temperatureгр/100,00 гр water
0°C
273.15 K
32 °F
491.67 °R
2.4
2.4 g/100g
2.344 %
10°C
283.15 K
50 °F
509.67 °R
4.99
4.99 g/100g
4.753 %
15°C
288.15 K
59 °F
518.67 °R
~6.37
6.37 g/100g
5.989 %
20°C
293.15 K
68 °F
527.67 °R
7.74
7.74 g/100g
7.184 %
25°C
298.15 K
77 °F
536.67 °R
9.19
9.19 g/100g
8.417 %
30°C
303.15 K
86 °F
545.67 °R
10.94
10.94 g/100g
9.861 %
40°C
313.15 K
104 °F
563.67 °R
14.88
14.88 g/100g
12.953 %
50°C
323.15 K
122 °F
581.67 °R
20.1
20.1 g/100g
16.736 %
60°C
333.15 K
140 °F
599.67 °R
26.7
26.7 g/100g
21.073 %
70°C
343.15 K
158 °F
617.67 °R
37.7
37.7 g/100g
27.378 %
80°C
353.15 K
176 °F
635.67 °R
53.9
53.9 g/100g
35.023 %
90°C
363.15 K
194 °F
653.67 °R
98.2
98.2 g/100g
49.546 %
100°C
373.15 K
212 °F
671.67 °R
121.0
121 g/100g
54.751 %
Insoluble in ethanol, acetone and glycerol.

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