Ferrous ammonium sulfate

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Pale green-blue crystals that slowly oxidize and effloresce in the presence of light and air. Known as Mohr's salt, ferrous ammonium sulfate is used as a primary standard in quantitative analysis. It is also used in photographic solutions and in Dosimeter badges.

Synonyms and Related Terms

Mohr's salt; ammonium ferrous sulfate; iron ammonium sulfate; ferrous ammonium sulphate (Br.); ammonium iron (II) sulfate


  • Contact may cause irritation.
  • May decompose in light.
  • Fisher Scientific: SDS

Physical and Chemical Properties

Soluble in water. Insoluble in ethanol. Deliquesces in air.

Composition FeSO4(NH4)2SO4.6H2O
CAS 10045-89-3
Melting Point 100-110 C (d)
Density 1.86 g/ml
Molecular Weight mol. wt. = 392.13

Resources and Citations

  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Susan E. Schur, Conservation Terminology: A review of Past & Current Nomenclature of Materials, Technology and Conservation, Spring (p.34-39); Summer (p.35-38); Fall (p.25-36), 1985