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| Iron(III)-ammonium sulfate | |
|---|---|
| Names: | ammonium-iron(III) sulfate monoammonium-iron(III) sulfate ferric-ammonium sulfate iron-ammonium alum iron alum ferric alum |
| Formula: | NH4Fe(SO4)2 (anhydrous) NH4Fe(SO4)2 · 12H2O (dodecahydrate) |
| Molar mass: | 266.006 g/mol (anhydrous) 482.184 g/mol (dodecahydrate) |
| Density: | 1.71 g/cm3 (dodecahydrate) |
| Crystal system: | monoclinic (trihydrate) a=9.982 Å, b=10.156 Å, c=9.504 Åα=90°, β=94.95°, γ=90° cubic (dodecahydrate) a=12.293 Å, b=12.293 Å, c=12.293 Åα=90°, β=90°, γ=90° |
| Shapes: | |
| Color: | light-violet pale-violet light-purple purple |
| Melting point: | 39 °C312.15 K <br />102.2 °F <br />561.87 °R <br /> (dodecahydrate) |
| Decomposition point: | 230 °C503.15 K <br />446 °F <br />905.67 °R <br /> (anhydrous) |
| Refractive index: | 1.4854 (dodecahydrate) |
| Stability: | erodes (dodecahydrate) hygroscopic (anhydrous) |
| Hardness: | strong |
| Toxicity: | slightly toxic |
Description
Inorganic compound, double salt of transitional metal iron, ammonium ion and inorganic sulfuric acid. From water solutions crystallizes as dodecahydrate.
Precursors
Reaction between pure iron, ammonium nitrate and sulfuric acid
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 11.58g of iron, 16.60g of ammonium nitrate and 109.95g of 37% sulfuric acid is required.Add acid to the flask, then add small parts of iron compound with stirring until it will totally dissolve . After reaction will stop, filter the solution and use it for crystal growing.
Reaction between iron and ammonium sulfates
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 63.88g of iron(III) sulfate dodecahydrate and 13.70g 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 Mohr's salt and hydrogen peroxide in sulfuric acid solution
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 81.32g of mohr's salt hexahydrate, 11.76g of 30% hydrogen peroxide and 27.49g of 37% sulfuric acid is required.Add to the flask with sulfuric acid solution hydrogen peroxide and then add small parts of {{{reducing_agent}}} with stirring until oxide emission will stop.
Reaction between iron(III) nitrate or chloride and ammonium sulfate
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 83.78g of iron(III) nitrate nonahydrate or 56.06g of iron(III) chloride hexahydrate and 54.81g 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 iron(III) sulfate and nitrate or ammonium chloride
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 85.18g of iron(III) sulfate dodecahydrate and 16.60g of ammonium nitrate or 11.09g 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 ammonium hydroxide, iron(III) hydroxide and sulfuric acid
Chemical equation:
100.00g of iron(III)-ammonium sulfate dodecahydrate а 7.27g of ammonium hydroxide, 22.16g of iron(III) hydroxide and 109.95g of 37% sulfuric acid is required.Add acid to the flask, then add small parts of ammonium and iron 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 ammonium alum.
Notes
Unlike chrome-potassium or chrome-ammonium alums, coating with a layer of other alum (for protection against erosion) is difficult - due to high solubility, placing a iron alum crystal to solution of other alums leads to crystal dissolving.
Storage conditions
For crystal storing use hermetic vessel with wadding moistened with such solution near the crystal. You can use such alternatives as vessel with vaseline or vegetable oil, organic non-hygroscopic solvent (kerosene or liquid paraffin). Also you can use acrylate polymer or another kinds of solidifying plastic.
Solubility
| Temperature | g/100,00 g water |
|---|---|
| 25°C298.15 K <br />77 °F <br />536.67 °R <br /> | 124 |
| 100°C373.15 K <br />212 °F <br />671.67 °R <br /> | 400 |
Gallery
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Crystal of iron-ammonium alum coated with a layer of aluminum-ammoniumIron(III)-ammonium sulfate, Dmitry Shintyakov, Personal crystal growing collectionPersonal crystal growing collection
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Crystal of chromium alum, coated with a layer of ferric alumIron(III)-ammonium sulfate, Maxim Martinov, VKontakteVKontakte
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Crystal of chromium alum, coated with a layer of ferric alumIron(III)-ammonium sulfate, Maxim Martinov, VKontakteVKontakte
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Crystal of chromium alum, coated with a layer of ferric alum, near a potassium alum crystalIron(III)-ammonium sulfate, Maxim Martinov, VKontakteVKontakte
Video
Sources
| Iron compounds | |
|---|---|
| Salts |
Iron (Fe) • Iron(II) acetate (Fe(CH3COO)2) • Iron(II) chloride (FeCl2) • Iron(III) chloride (FeCl3) • Iron(II) citrate (FeHC3H5O(COO)3) • Iron(II) formate (Fe(COOH)2) • Iron(III) formate (Fe2(COOH)3) • Iron(II) nitrate (Fe(NO3)2) • Iron(II) phosphate (Fe3(PO4)2) • Iron(II) sulfate (FeSO4) • Iron(III) sulfate (Fe2(SO4)3) |
| Double salts |
Iron(III)-ammonium sulfate ((NH4)Fe(SO4)2) • Iron(II)-ammonium sulfate ((NH4)2Fe(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Iron(II)-magnesium sulfate ((Fe,Mg)SO4) • Copper(II)-iron(II) sulfate ((Cu,Fe)SO4) |
| Complexes |
Hexacyanoferrates • Nitroprussides • Pentachloroferrates • Trioxalatoferrates • Sodium ethylenediaminetetraacetate-ferrate(III) (Na[Fe((OOCCH2)2N(CH2)2N(CH2COO)2)]) |







