Ammonium iron(III) sulfate

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Ammonium iron(III) sulfate
Ferric amm sulfate.jpg
Ferric Ammonium Sulfate Dodecahydrate formula.png
Names
IUPAC name
Ammonium iron(III) sulfate
Other names
Ferric ammonium sulfate
Ferric alum
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.107.412
EC Number 233-382-4
UNII
Properties
FeNH4(SO4)2•12H2O
Molar mass 482.25 g/mol (dodecahydrate)
Appearance Pale violet octahedral crystals
Odor weak ammonia-like
Density 1.71 g/cm3
Melting point 39 to 41 °C (102 to 106 °F; 312 to 314 K)
1240 g/L
Hazards
Main hazards Irritant (Xi)
Related compounds
Other anions
Ammonium iron(III) citrate
Ammonium chloride
Other cations
Ammonium aluminium sulfate
potassium aluminium sulfate
Related compounds
Ammonium iron(II) sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Ammonium iron(III) sulfate, NH4Fe(SO4)2·12 H2O, or NH4[Fe(H2O)6](SO4)2·6 H2O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO4)2 · 12 H2O.[1] It has the appearance of weakly violet, octahedrical crystals. There has been some discussion regarding the origin of the crystals' colour, with some ascribing it to impurities in the compound,[2] and others claiming it to be a property of the crystal itself.[3]

FAS is paramagnetic,[4] acidic and toxic towards microorganisms.[5] It is a weak oxidizing agent, capable of being reduced to Mohr's salt, ferrous ammonium sulfate.

Preparation[edit]

FAS can be prepared by crystallization from a solution of ferric sulfate and ammonium sulfate. Iron(II) in ferrous sulfate is oxidized to Iron(III) in ferric sulfate by addition of sulfuric and nitric acid. Upon addition of ammonium sulfate to the solution and damping in of the solution, ferric ammonium sulfate crystals will precipitate.

Oxidation: 6 FeSO4 + 2 HNO3 + 3 H2SO4 = 3 Fe2(SO4)3 + 2 NO + 4 H2O

Synthesis: Fe2(SO4)3 + (NH4)2SO4 = 2 NH4Fe(SO4)2

Procedure[6]:

The nitric and sulfuric acid is reacted with the ferrous sulfate to make ferric sulfate, nitric oxide, and water. The ferric sulfate is mixed with ammonium sulfate and crystallized to get ammonium iron(III) sulfate. The solution is normally tested to ensure that no more iron(II) is left.

Uses[edit]

Areas of use for FAS include waste water treatment,[7] tanning,[7] production of dyestuffs,[7] and as an etching agent in the production of electronic components.[8] It has been used in a wide area of applications, including adiabatic refrigeration equipment,[9] biochemical analysis[10] and organic synthesis.[11]

Gallery[edit]

References[edit]

  1. ^ Considine, Douglas M: Chemical and process technology encyclopedia, McGraw-Hill, New York, 1974, p. 993
  2. ^ Christensen, Odin T. "On the Cause of the Amethyst Color of Ferric Alum and of Mixed Crystals of Ferric and Manganic Alum". Chem. Lab. Roy. Vet. Agr. Hochschule, Kgl. Danske Vidsk. Selsk. Forh. 1906: 173–95. 
  3. ^ Bonnell, Jane; Philip Perman, Edgar (1921). "CCXXIX.—The colour of iron alum". J. Chem. Soc., Trans. 119: 1994–1997. doi:10.1039/CT9211901994. 
  4. ^ Cooke, Meyer; Wolf. "The Specific Heats of Three Paramagnetic salts at Very Low Temperatures". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. 237 (1210): 395–403. doi:10.1098/rspa.1956.0185. 
  5. ^ Wang, Fei; et al. "Microcalorimetric investigation of the toxic action of ammonium ferric(III)sulfate on the metabolic activity of pure microbes". Environmental Toxicology and Pharmacology. 25: 351–357. doi:10.1016/j.etap.2007.11.004. 
  6. ^ Hecht, Horstmar: Prãparative Anorganische Chemie, Springer-Verlag, Berlin, 1951. p. 127
  7. ^ a b c Wiley Encyclopedia of inorganic chemistry: Volume 4, p. 1704:
  8. ^ Chen et al.: United States Patent 5518131 - "Etching molydbenum with ferric sulfate and ferric ammonium sulfate"
  9. ^ Grant W. Wilson, Peter T. Timbie: Construction techniques for adiabatic demagnetization refrigerators using ferric ammonium alum. Cryogenics, *Volume 39, Number 4, (1999) , p. 319–322
  10. ^ J. C. Whitehorn: A system of blood analysis. Supplement II. Simplified method for the determination of chlorides in blood or plasma. *Journal of Biological Chemistry (1921), 45 p. 449–60.
  11. ^ Yu, Shanxin; et al. (2005). "Application of ammonium ferric sulfate dodecahydrate in organic synthesis". General Review. 17 (1): 27–30. 
Salts and esters of the sulfate ion
H2SO4 He
Li2SO4 BeSO4 B esters
ROSO3
(RO)2SO2
(NH4)2SO4
[N2H5]HSO4
(NH3OH)2SO4
NOHSO4
HOSO4 F Ne
Na2SO4
NaHSO4
MgSO4 Al2(SO4)3
Al2SO4(OAc)4
Si P SO42−
HSO3HSO4
(HSO4)2
Cl Ar
K2SO4
KHSO4
CaSO4 Sc2(SO4)3 Ti(SO4)2
TiOSO4
VSO4
V2(SO4)3
VOSO4
CrSO4
Cr2(SO4)3
MnSO4
Mn2(SO4)3
FeSO4
Fe2(SO4)3
CoSO4
Co2(SO4)3
NiSO4 CuSO4
Cu2SO4
[Cu(NH3)4(H2O)]SO4
ZnSO4 Ga2(SO4)3 Ge As Se Br Kr
RbHSO4
Rb2SO4
SrSO4 Y2(SO4)3 Zr(SO4)2 Nb Mo Tc Ru Rh PdSO4 Ag2SO4 CdSO4 In2(SO4)3 SnSO4 Sb2(SO4)3 Te I Xe
Cs2SO4 BaSO4   Hf Ta W Re Os Ir Pt Au Hg2SO4
HgSO4
Tl2SO4
Tl2(SO4)3
PbSO4 Bi2(SO4)3 Po At Rn
Fr Ra   Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
La Ce2(SO4)3
Ce(SO4)2
Pr2(SO4)3 Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb2(SO4)3 Lu
Ac Th Pa U(SO4)2
UO2SO4
Np Pu Am Cm Bk Cf Es Fm Md No Lr