Ammonium iron(II) sulfate

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Ammonium iron(II) sulfate
Ammonium Iron(II) sulfate hexahydrate sample.jpg
Sample of Mohr's salt and original bottle
Names
IUPAC name
Ammonium iron(II) sulfate
Other names
Ammonium iron sulfate
Diammonium iron(II) sulfate
Ferrous ammonium sulfate
Mohr's salt
Properties
FeH8N2O8S2
(NH4)2Fe(SO4)2 (anhydrous)
(NH4)2Fe(SO4)2·6 H2O (hexahydrate)
Molar mass 284.05 g/mol (anhydrous)
392.13 g/mol (hexahydrate)
Appearance Light blue or green solid
Odor Odorless
Density 1.86 g/cm3 (20 °C)
Melting point 100–110 °C (212–230 °F; 373–383 K) (decomposes)
Boiling point Decomposes
hexahydrate
26.9 g/100 ml
Solubility Insoluble in esters, ethers, hydrocarbons
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Sigma-Aldrich (hexahydrate)
Flash point Non-flammable
Related compounds
Related compounds
Ammonium sulfate
Iron(II) sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ammonium iron(II) sulfate, more commonly referred to as Mohr's salt, is an inorganic chemical compound with the formula (NH4)2Fe(SO4)2·6 H2O as hexahydrate. Containing two different cations, Fe2+ and NH4+, it is classified as a double salt of ferrous sulfate and ammonium sulfate.

Properties

Chemical

Addition of a base like sodium hydroxide will precipitate iron(II) hydroxide, releasing ammonia gas.

Unlike other Fe2+ compounds, Mohr's salt resists air oxidation much better, which makes it useful in analytical chemistry.

Physical

Ammonium iron (II) sulphate is a light blue or greenish solid, soluble in water.

Availability

Ammonium iron(II) sulphate is sold by chemical suppliers. Can also be bought online.

Preparation

Mohr's salt is prepared by dissolving an equimolar mixture of iron(II) sulfate heptahydrate and ammonium sulfate in water, with a bit of sulfuric acid. The solution is cooled to crystallize the compound.

Projects

  • Grow crystals
  • Source of ferrous ions in chemical reactions

Handling

Safety

Ammonium iron(II) sulphate has low toxicity, though contact with strong bases will release irritant ammonia fumes.

Storage

Mohr's salt should be kept in closed bottles.

Disposal

No special disposal is required. Mohr's salt can be used as nitrogen, iron and sulfur fertilizer.

References

Relevant Sciencemadness threads