Aluminum-potassium sulfate

From Crystal growing

<amp/>


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

Formula: KAl(SO4)2 (anhydrous)
KAl(SO4)2 · 12H2O (dodecahydrate)
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, b=4.7206 Å, c=7.9835 Åα=90°, β=90°, γ=120°
cubic (dodecahydrate)
a=12.164 Å, b=12.164 Å, c=12.164 Åα=90°, β=90°, γ=90°
Shapes:
https://en.crystalls.info/w/uploads/media/Octahedron.json
https://en.crystalls.info/w/uploads/media/Tetragonal_pyramid.json
https://en.crystalls.info/w/uploads/media/Truncated_octahedron.json
https://en.crystalls.info/w/uploads/media/Cuboctahedron.json
https://en.crystalls.info/w/uploads/media/Cube.json

Color: colorless
Melting point: 92.5 °C365.65 K <br />198.5 °F <br />658.17 °R <br /> (dodecahydrate)
Refractive index: 1.4564 (dodecahydrate)
Radiation properties: slightly radioactive
Stability: stable (dodecahydrate)
hygroscopic (anhydrous)
Hardness: relatively strong
(2 on Moh's scale)
Toxicity: slightly toxic
LD50~2000mg/kg

Description

Inorganic compound, double salt of transitional metal aluminum, 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).

Precursors

Reaction between aluminum and potassium sulfates

Chemical equation:

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


For preparation of 100.00g of aluminum-potassium sulfate dodecahydrate а 70.24g of aluminum sulfate octadecahydrate 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 aluminum, potassium nitrate and sulfuric acid

Chemical equation:

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


For preparation of 100.00g of aluminum-potassium sulfate dodecahydrate а 5.69g of aluminum, 21.31g of potassium nitrate and 111.76g 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 potassium sulfate

Chemical equation:

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


For preparation of 100.00g of aluminum-potassium sulfate dodecahydrate а 79.08g of aluminum nitrate nonahydrate or 50.89g of aluminum chloride hexahydrate 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 aluminum 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 of 100.00g of aluminum-potassium sulfate dodecahydrate а 93.65g of aluminum sulfate octadecahydrate 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, aluminum 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 of 100.00g of aluminum-potassium sulfate dodecahydrate а 11.83g of potassium hydroxide or 14.57g of potassium carbonate, 16.44g of aluminum hydroxide and 111.76g of 37% sulfuric acid is required.

Add acid to the flask, then add small parts of potassium 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°C273.15 K <br />32 °F <br />491.67 °R <br />3
10°C283.15 K <br />50 °F <br />509.67 °R <br />4
15°C288.15 K <br />59 °F <br />518.67 °R <br />~4.95
20°C293.15 K <br />68 °F <br />527.67 °R <br />5.9
25°C298.15 K <br />77 °F <br />536.67 °R <br />7.23
30°C303.15 K <br />86 °F <br />545.67 °R <br />8.39
40°C313.15 K <br />104 °F <br />563.67 °R <br />11.7
50°C323.15 K <br />122 °F <br />581.67 °R <br />17
60°C333.15 K <br />140 °F <br />599.67 °R <br />24.75
70°C343.15 K <br />158 °F <br />617.67 °R <br />40
80°C353.15 K <br />176 °F <br />635.67 °R <br />71
90°C363.15 K <br />194 °F <br />653.67 °R <br />109
100°C373.15 K <br />212 °F <br />671.67 °R <br />154
Insoluble in ethanol.


Gallery


Video


Sources


Navigation