Chromium(III)-potassium sulfate
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Chromium(III)-potassium sulfate | |
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Names: | potassium-chromium(III) sulfate monopotassium-chromium(III) sulfate chromium-potassium alum |
Formula: | KCr(SO4)2 (anhydrous) KCr(SO4)2 · 12H2O (dodecahydrate) |
SMILES: | [O-]S(=O)(=O)[O-].[O-]S(=O)(=O)[O-].[Cr+3].[K+] |
Molar mass: | 283.216 g/mol (anhydrous) 499.395 g/mol (dodecahydrate) |
Density: | 1.842 g/cm3 (dodecahydrate) |
Crystal system: | hexagonal (anhydrous) a=4.7261 Å, b=4.7261 Å, c=8.0483 Åα=90°, β=90°, γ=120° cubic (dodecahydrate) a=12.2305 Å, b=12.2305 Å, c=12.2305 Åα=90°, β=90°, γ=90° |
Shapes: |
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Color: | violet blue-violet purple red |
Decomposition point: | 89 °C362.15 K <br />192.2 °F <br />651.87 °R <br /> (dodecahydrate) 350 °C623.15 K <br />662 °F <br />1,121.67 °R <br /> (anhydrous) |
Refractive index: | 1.4564 (dodecahydrate) |
Stability: | erodes (dodecahydrate) hygroscopic (anhydrous) |
Hardness: | strong |
Toxicity: | highly toxic |
Description
Inorganic compound, double salt of transitional metal chromium, alkaline metal potassium and inorganic sulfuric acid. From water solutions crystallizes as dodecahydrate.
Precursors
Reaction between chromium and potassium sulfates
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 60.91
g of chromium(III) sulfate dodecahydrate
and 17.45
g 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 potassium dichromate, sulfuric acid and hydrogen peroxide
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 29.45
g of potassium dichromate, 34.06
g of 30%
peroxide and 106.16
g of 37%
sulfuric acid is required.Add to the flask with sulfuric acid solution hydrogen peroxide and then add small parts of potassium dichromate with stirring until a precipitation forming will stop. Filter precipitate and wash it wish small amount of ethanol or acetone, then filter the solution and use it for crystal growing.
Reaction between potassium dichromate, sulfuric acid and any reducing agentsuch as ethanol, isopropanol, oxalic acid, formic acid or glucose
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 29.45
g of potassium dichromate, 13.84
g of ethanol or 18.05
g of isopropanol or 27.04
g of oxalic acid or 5.31
g of 85%
formic acid or 4.51
g of glucose and 106.16
g of 37%
sulfuric acid is required.Add to the flask saturated solution of sulfuric acid and potassium dichromate and then add small parts of hot reducing agent solution with heating and stirring. Emission of large amount of gas will begin.Attention, exuding gas irritates eyes and lungs! The synthesis should be carried out only in a fume hood or outdoors!
Reaction between pure chromium, potassium nitrate and sulfuric acid
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 10.41
g of chromium, 20.24
g of potassium nitrate and 106.16
g of 37%
sulfuric acid is required.Add acid to the flask, then add small parts of chromium compound with stirring until it will totally dissolve . After reaction will stop, filter the solution and use it for crystal growing.
Reaction between chromium(III) nitrate or chloride and potassium sulfate
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 80.13
g of chromium(III) nitrate nonahydrate
or 53.35
g of chromium(III) chloride hexahydrate
and 69.79
g 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 chromium(III) sulfate and nitrate or potassium chloride
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 81.21
g of chromium(III) sulfate dodecahydrate
and 20.24
g of potassium nitrate or 14.93
g 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, chromium(III) hydroxide and sulfuric acid
Chemical equation:
100.00
g of chromium(III)-potassium sulfate dodecahydrate
а 11.23
g of potassium hydroxide or 13.84
g of potassium carbonate, 20.63
g of chromium(III) hydroxide and 106.16
g of 37%
sulfuric acid is required.Add acid to the flask, then add small parts of potassium and chromium 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 potassium alum.
Notes
Due to crystal erosion in the air, they are usually coated with a layer of potassium alum. Alums are isomorphous between each other, so they are not dissolving in saturated solution of other alums.
Also, you can combine alums in one solution, getting crystals of other shades.
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
Gallery
Growth during 1.5 monthChromium(III)-potassium sulfate, Aleksandr Chernikh, VKontakteVKontakte
Mixture of potassium and chromium alum. Grown during 2 weeksAluminum-potassium sulfate, Stanislav Popov, VKontakteVKontakte
Mixture of potassium and chromium alum in 9:1 ratioChromium(III)-potassium sulfate, Rostislav Dolgikh, VKontakteVKontakte
Mixture of potassium and chromium alumChromium(III)-potassium sulfate, Stanislav Popov, VKontakteVKontakte
Mixture of potassium and chromium alumChromium(III)-potassium sulfate, Vasily Furt, VKontakteVKontakte
Crystal of mixture pf potassium and chrome alum, coated with a layer of pure potassium alumChromium(III)-potassium sulfate, Aleksandr Pavlushin, VKontakteVKontakte
Crystal of mixture pf potassium and chrome alum, coated with a layer of pure potassium alumChromium(III)-potassium sulfate, Aleksandr Pavlushin, VKontakteVKontakte
Video
Sources
Chromium compounds | |
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Salts |
Chromates • Chromium(II) acetate (Cr(CH3COO)2) • Chromium(III) sulfate (Cr2(SO4)3) • Chromium(III)-ammonium sulfate (NH4Cr(SO4)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) |
Complexes |