Ammonium iron(III) sulfate
Encyclopedia
Ammonium iron sulfate, NH4Fe(SO4)2·12 H2O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt
in the class of alum
s, which consists of compounds with the general formula AB(SO4)2 · 12 H2O. It has the appearance of weakly violet, octahedrical crystal
s. There has been some discussion regarding the origin of the crystals' colour, with some ascribing it to impurities in the compound, and others claiming it to be a property of the crystal itself.
FAS is paramagnetic
, acidic and toxic
towards microorganism
s. It is a weak oxidizing agent, capable of being reduced to Mohr's salt
, ferrous ammonium 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:
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.
, production of dye
stuffs, and as an etching
agent in the production of electronic components
. It has been used in a wide area of applications, including adiabatic refrigeration
equipment, biochemical analysis and organic synthesis
.
Double salt
Double salts are salts containing more than one cation or anion. They form when more than one salt is dissolved in a liquid and when together they crystallize in a regular pattern. A well-known double salt is alum containing two cations and a sulfate anion...
in the class of alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...
s, which consists of compounds with the general formula AB(SO4)2 · 12 H2O. It has the appearance of weakly violet, octahedrical crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s. There has been some discussion regarding the origin of the crystals' colour, with some ascribing it to impurities in the compound, and others claiming it to be a property of the crystal itself.
FAS is paramagnetic
Paramagnetism
Paramagnetism is a form of magnetism whereby the paramagnetic material is only attracted when in the presence of an externally applied magnetic field. In contrast with this, diamagnetic materials are repulsive when placed in a magnetic field...
, acidic and toxic
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
towards microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. It is a weak oxidizing agent, capable of being reduced to Mohr's salt
Mohr's salt
Ammonium iron sulfate, or Mohr's Salt, is the inorganic compound with the formula 2Fe2·6H2O. Containing two different cations, Fe2+ and NH4+, it is classified as a double salt of ferrous sulfate and ammonium sulfate. It is a common laboratory reagent...
, ferrous ammonium sulfate.
Preparation
FAS can be prepared by crystallization from a solution of ferric sulfateIron(III) sulfate
Iron sulfate , is the chemical compound with the formula Fe23, the sulfate of trivalent iron. Usually yellow, it is a rhombic crystalline salt and soluble in water at room temperature. It is used in dyeing as a mordant, and as a coagulant for industrial wastes. It is also used in pigments, and in...
and ammonium sulfate
Ammonium sulfate
Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
. Iron(II) in ferrous sulfate is oxidized to Iron(III) in ferric sulfate by addition of sulfuric
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
and nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
. 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:
The nitric and sulfuric acid is reacted with the ferrous sulfate to make ferric sulfate, nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
, and water. The ferric sulfate is mixed with ammonium sulfate
Ammonium sulfate
Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
and crystallized to get ammonium iron(III) sulfate. The solution is normally tested to ensure that no more iron(II) is left.
Uses
Areas of use for FAS include waste water treatment, tanningTanning
Tanning is the making of leather from the skins of animals which does not easily decompose. Traditionally, tanning used tannin, an acidic chemical compound from which the tanning process draws its name . Coloring may occur during tanning...
, production of dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
stuffs, and as an etching
Etching
Etching is the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal...
agent in the production of electronic components
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
. It has been used in a wide area of applications, including adiabatic refrigeration
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...
equipment, biochemical analysis and organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
.