Aluminum-potassium sulfate

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Crystal compoundsSaltsSulfatesAluminum-potassium sulfate



  Aluminum-potassium sulfate   
Names: aliminum(III)-potassium sulfate
potassium-aliminum sulfate
potassium alum
potash alum

Formula: KAl(SO4)2
KAl(SO4)2 · 12H2O
SMILES: [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Al+3].[K+]
Molar mass: 258.202 g/mol (anhydrous)
474.381 g/mol (dodecahydrate)
Density: 2.75 g/cm3 (anhydrous)
1.725 g/cm3 (dodecahydrate)
Crystal system: hexagonal (anhydrous)
a=4.7206 Å
4.7206 Å
0.4721 nm
, b=4.7206 Å
4.7206 Å
0.4721 nm
, c=7.9835 Å
7.9835 Å
0.7984 nm
α=90°
90°  
, β=90°
90°  
, γ=120°
120°  

cubic (dodecahydrate)
a=12.164 Å
12.1640 Å
1.2164 nm
, b=12.164 Å
12.1640 Å
1.2164 nm
, c=12.164 Å
12.1640 Å
1.2164 nm
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

Forms:
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
Melting point: 92.5°C
365.65 K
198.5 °F
658.17 °R
(dodecahydrate)
Decomposition point: 120°C
393.15 K
248 °F
707.67 °R
(dodecahydrate)
850°C
1,123.15 K
1,562 °F
2,021.67 °R
(anhydrous)
Refractive index: 1.4564 (dodecahydrate)
Electrical properties: dielectric
Stability: stable (dodecahydrate)
hygroscopic (anhydrous)
Hardness: strong
Toxicity: non-toxic

==Description == Inorganic compound, double salt of transitional metal aliminum, alkaline metal potassium and inorganic sulfuric acid. From water solutions crystallizes as dodecahydrate.

Minerals

Occurs in nature as alum-(K), kalinite, alunite and steklite minerals.

Where to buy

In pharmacy (as "burnt alum" or "crystal deodorant" - dehydrated alum).

Synthesis

Reaction between aliminum and potassium sulfates

Chemical equation:

K2SO4 + Al2(SO4)3 = 2KAl(SO4)2

For preparation 100g of aliminum-potassium sulfate dodecahydrate a 70.24g of aliminum sulfate octadecahydrate or 36.06g of anhydrous aliminum sulfate and 18.37g of potassium 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 aliminum, potassium nitrate and sulfuric acid==== Chemical equation:

2H2SO4 + KNO3 + Al = KAl(SO4)2 + NO↑ + 2H2O

For preparation 100g of aliminum-potassium sulfate dodecahydrate a 5.69g of aliminum or 10.66g of potassium nitrate and 121.62g of 34% sulfuric acid is required.
Add potassium nitrate to acid solution. Add acid to the flask, then add small parts of aliminum compound with stirring until it will totally dissolve . Attention, exuding nitric oxide irritates eyes and lungs! The synthesis should be carried out only in a fume hood or outdoors! After reaction will stop, filter the solution and use it for crystal growing.

====Reaction between aluminum nitrate or chloride and potassium sulfate==== Chemical equation:

2K2SO4 + Al(NO3)3 = KAl(SO4)2 + 3KNO3
2K2SO4 + AlCl3 = KAl(SO4)2 + 3KCl

For preparation 100g of aliminum-potassium sulfate dodecahydrate a 79.08g of aliminum nitrate nonahydrate, 44.90g of anhydrous aliminum nitrate, 50.89g of aliminum chloride hexahydrate or 28.11g of anhydrous aliminum chloride and 73.47g of potassium 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 aliminum sulfate and nitrate or potassium chloride==== Chemical equation:

3KNO3 + 2Al2(SO4)3 = 3KAl(SO4)2 + Al(NO3)3
3KCl + 2Al2(SO4)3 = 3KAl(SO4)2 + AlCl3

For preparation 100g of aliminum-potassium sulfate dodecahydrate a 93.65g of aliminum sulfate octadecahydrate or 48.08g of anhydrous aliminum sulfate and 21.31g of potassium nitrate or 15.72g of potassium 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 potassium hydroxide or carbonate, aliminum hydroxide and sulfuric acid==== Chemical equation:

2H2SO4 + KOH + Al(OH)3 = KAl(SO4)2 + 4H2O
4H2SO4 + K2CO3 + 2Al(OH)3 = 2KAl(SO4)2 + 7H2O + CO2

For preparation 100g of aliminum-potassium sulfate dodecahydrate a 11.83g of potassium hydroxide, 14.57g of potassium carbonate or 16.44g of aliminum hydroxide and 121.62g of 34% sulfuric acid is required.
Add acid to the flask, then add small parts of potassium and aliminum 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 the shape of the crystals - small amounts lead to beveling of crystal corners, large amounts lead to changing crystal shape to cuboctahedron and then to 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

Temperatureg/100g of water
(dodecahydrate)
0°C
273.15 K
32 °F
491.67 °R
3
3 g/100g
2.913 %
10°C
283.15 K
50 °F
509.67 °R
4
4 g/100g
3.846 %
15°C
288.15 K
59 °F
518.67 °R
~4.95
4.95 g/100g
4.717 %
20°C
293.15 K
68 °F
527.67 °R
5.9
5.9 g/100g
5.571 %
25°C
298.15 K
77 °F
536.67 °R
7.23
7.23 g/100g
6.743 %
30°C
303.15 K
86 °F
545.67 °R
8.39
8.39 g/100g
7.741 %
40°C
313.15 K
104 °F
563.67 °R
11.7
11.7 g/100g
10.474 %
50°C
323.15 K
122 °F
581.67 °R
17
17 g/100g
14.53 %
60°C
333.15 K
140 °F
599.67 °R
24.75
24.75 g/100g
19.84 %
70°C
343.15 K
158 °F
617.67 °R
40
40 g/100g
28.571 %
80°C
353.15 K
176 °F
635.67 °R
71
71 g/100g
41.52 %
90°C
363.15 K
194 °F
653.67 °R
109
109 g/100g
52.153 %
100°C
373.15 K
212 °F
671.67 °R
154
154 g/100g
60.63 %
Insoluble in ethanol.

==Gallery==


==Video==


==Sources==


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