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Aluminum-potassium sulfate

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   Aluminum-potassium sulfate   
Names: aluminum(III)-potassium sulfate
potassium-aluminum sulfate
potassium alum
potash alum
Е522 food additive
Formula: KAl(SO4)2 (anhydrous)
KAl(SO4)2 · 12H2O (dodecahydrate)
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/3/37/Octahedron.json
Octahedron
https://en.crystalls.info/w/uploads/media/8/8f/Tetragonal_pyramid.json
Tetragonal pyramid
https://en.crystalls.info/w/uploads/media/f/f7/Truncated_octahedron.json
Truncated octahedron
https://en.crystalls.info/w/uploads/media/4/4a/Cuboctahedron.json
Cuboctahedron
https://en.crystalls.info/w/uploads/media/f/f1/Cube.json
Cube

Color: colorless
Melting point: 92.5 °C365.65 K <br />198.5 °F <br />658.17 °R <br /> (dodecahydrate)
Refractive index: 1.4564 (dodecahydrate)
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

Can be bought 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 potassium nitrate or 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.

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.

Notes

Crystalverse.com site provides a step-by-step guide about growing big crystals of potassium alum.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

Temperatureg/100,00 g 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
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.


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   Sulfates
Simple

Aluminum sulfate (Al2(SO4)3) • Ammonium sulfate ((NH4)2SO4) • Calcium sulfate (CaSO4) • Cadmium sulfate (CdSO4) • Cerium(III) sulfate (Ce2(SO4)3) • Cerium(IV) sulfate (Ce(SO4)2) • Chromium(III) sulfate (Cr2(SO4)3) • Cobalt(II) sulfate (CoSO4) • Copper(II) sulfate (CuSO4) • Gadolinium sulfate (Gd2(SO4)3) • Holmium sulfate (Ho2(SO4)3) • Hydrazine sulfate (N2H4 · H2SO4) • Iron(II) sulfate (FeSO4) • Iron(III) sulfate (Fe2(SO4)3) • Lanthanum sulfate (La2(SO4)3) • Lithium sulfate (Li2SO4) • Magnesium sulfate (MgSO4) • Manganese(II) sulfate (MnSO4) • Neodymium sulfate (Nd2(SO4)3) • Nickel sulfate (NiSO4) • Potassium sulfate (K2SO4) • Praseodymium(III) sulfate (Pr2(SO4)3) • Rubidium sulfate (Rb2SO4) • Sodium hydrosulfate (NaHSO4) • Sodium sulfate (Na2SO4) • Yttrium sulfate (Gd2(SO4)3) • Zinc sulfate (ZnSO4)

Alums

Aluminum-ammonium sulfate (NH4Al(SO4)2) • Aluminum-potassium sulfate (KAl(SO4)2) • Chromium(III)-ammonium sulfate (NH4Cr(SO4)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) • Cobalt(III)-ammonium sulfate (NH4Co(SO4)2) • Indium(III)-potassium sulfate (KIn(SO4)2) • Iron(III)-ammonium sulfate (NH4Fe(SO4)2) • Iron(III)-potassium sulfate (KFe(SO4)2) • Manganese(III)-ammonium sulfate (NH4Mn(SO4)2) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2)

Tutton's salts

Chromium(II)-ammonium sulfate ((NH4)2Cr(SO4)2) • Cobalt(II)-ammonium sulfate ((NH4)2Co(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) • Copper(II)-ammonium sulfate ((NH4)2Cu(SO4)2) • Copper(II)-potassium sulfate (K2Cu(SO4)2) • Iron(II)-ammonium sulfate ((NH4)2Fe(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Magnesium-ammonium sulfate ((NH4)2Mg(SO4)2) • Magnesium-potassium sulfate (K2Mg(SO4)2) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4) • Manganese(II)-ammonium sulfate ((NH4)2Mn(SO4)2) • Manganese(II)-potassium sulfate (K2Mn(SO4)2) • Nickel-ammonium sulfate ((NH4)2Ni(SO4)2) • Nickel-potassium sulfate (K2Ni(SO4)2) • Vanadium(II)-ammonium sulfate ((NH4)2V(SO4)2) • Zinc-ammonium sulfate ((NH4)2Zn(SO4)2) • Zinc-potassium sulfate (K2Zn(SO4)2)

Double salts

Copper(II)-iron(II) sulfate ((Cu,Fe)SO4) • Iron(II)-magnesium sulfate ((Fe,Mg)SO4) • Lithium-potassium sulfate (KLiSO4) • Sodium-ammonium sulfate (NaNH4SO4) • Zinc-sodium sulfate (Na2Zn(SO4)2)

Adducts

Triglycine sulfate ((NH2CH2COOH)3 · H2SO4) • Glutamic acid sulfate (C5H9NO4 · H2SO4)

Complexes

Cerium(III) sulfocerate(IV) (Ce4[Ce(SO4)4]3) • Glycinecopper(II) sulfate ([Cu(NH2CH2COOH)]SO4) • Hexakarbamatzinc sulfate ([(CON2H4)6Zn]SO4) • Tetraamminecopper(II) sulfate ([Cu(NH3)4]SO4) • Tris(hydroxymethil)methanoaminecopper(II) sulfate ([Cu(NH2C(CH2OH)3)4]SO4)


   Potassium compounds
Salts

Potassium bromate (KBrO3) • Potassium bromide (KBr) • Potassium chlorate (KClO3) • Potassium chloride (KCl) • Potassium chromate (K2CrO4) • Potassium dihydrophosphate (KH2PO4) • Potassium dichromate (K2Cr2O7) • Potassium iodide (KI) • Potassium hydrofluoride (KHF2) • Potassium hydrophosphate (K2HPO4) • Potassium hydrophthalate (KC8H6O4) • Potassium metavanadate (KVO3) • Potassium nitrate (KNO3) • Potassium sulfate (K2SO4) • Potassium thiocyanate (KNCS)

Double salts

Aluminum-potassium sulfate (KAl(SO4)2) • Antimony(III)-potassium tartrate (K2Sb2(C4H2O6)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) • Copper(II)-potassium sulfate (K2Cu(SO4)2) • Indium(III)-potassium sulfate (KIn(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Iron(III)-potassium sulfate (KFe(SO4)2) • Lithium-potassium sulfate (KLiSO4) • Magnesium-potassium sulfate (K2Mg(SO4)2) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4) • Manganese(II)-potassium sulfate (K2Mn(SO4)2) • Nickel-potassium sulfate (K2Ni(SO4)2) • Potassium-sodium tartrate (KNaC4H4O6) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2) • Zinc-potassium sulfate (K2Zn(SO4)2)

Complexes

Potassium dioxalatocuprate(II) (K2[Cu(C2O4)2]) • Potassium hexanitrocobaltate(III) (K3[Co(NO2)6]) • Potassium hexachlororhodiate(III) (K3[RhCl6]) • Potassium hexacyanocobaltate(III) (K3[Co(CN)6]) • Potassium hexacyanoferrate(II) (K4[Fe(CN)6]) • Tripotassium-sodium hexacyanoferrate(II) (K3Na[Fe(CN)6]) • Potassium hexacyanoferrate(III) (K3[Fe(CN)6]) • Potassium hexacyanochromate(III) (K3[Co(CN)6]) • Potassium tetraiodobismuthate (К[BiI4]) • Potassium tetraiodomercurate(II) (K2[HgI4]) • Potassium trioxalatoaluminate (K3[Al(C2O4)3]) • Potassium trioxalatocobaltate(III) (K3[Co(C2O4)3]) Potassium trioxalatoferrate(III) (K3[Fe(C2O4)3]) • Potassium-sodium trioxalatoferrate(III) (K5Na[Fe(C2O4)3]2) • Dipotassium-sodium trioxalatoferrate(III) (K2Na[Fe(C2O4)3]) • Potassium trioxalatochromate(III) (K3[Cr(C2O4)3])


   Aluminum compounds
Simple

Aluminum sulfate (Al2(SO4)3) • Aluminum-ammonium sulfate (NH4Al(SO4)2) • Aluminum-potassium sulfate (KAl(SO4)2)

Complex
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