Ammonium iron(II)sulfate hexahydrate
| Formula | H8FeN2O8S2*6H2O |
| Chemical formula | H8FeN2O8S2*6H2O |
| Molar mass | 177.99 g/mol |
| CAS number | 7783-85-9 |
| HS Code | 2842 90 00 |
| EC number | 233-151-8 |
| Storage | 15 C to 30C |
| SDS | available |
| Form | solid |
| pH value | 3.0 to 5.0 |
| Solubility in water | 269g/l (20°C) |
| Melting point | 39 to 100 °C |
| Assay | 99.0 to 101.5 | ||
| Description | Conforms | ||
| Identification | Conforms | ||
| pH-value (5%in water) | 3.0-to 5.0 | % | |
| Chloride | ≤ | 0.0010 | % |
| Phosphate | ≤ | 0.0020 | % |
| Heavy metal | ≤ | 0.0010 | % |
| Calcium | ≤ | 0.0020 | % |
| Copper | ≤ | 0.0020 | % |
| Magneslum | ≤ | 0.0100 | % |
| Manganese | ≤ | 0.0100 | % |
| Iron III | ≤ | 0.0200 | % |
| Zinc | ≤ | 0.0030 | % |
| Sodium | ≤ | 0.01 | % |
Ammonium iron(II) sulfate hexahydrate is a light green, crystalline compound commonly used in analytical chemistry. It is a double salt of ferrous sulfate and ammonium sulfate and is well known for its stability and reliability as a primary standard in redox titrations.
🏭⚗️ Production
Ammonium iron(II) sulfate hexahydrate is prepared by mixing aqueous solutions of ferrous sulfate and ammonium sulfate, followed by controlled crystallization. The product is typically recrystallized from water and cooled to allow the formation of hexahydrate crystals. This double salt is also known as Mohr’s salt and is valued for its resistance to oxidation in air compared to simple iron(II) salts.
🔬 Properties
The chemical formula of ammonium iron(II) sulfate hexahydrate is (NH₄)₂Fe(SO₄)₂·6H₂O, with a molar mass of approximately 392.14 g/mol. It forms pale green crystals that are soluble in water but insoluble in alcohol. It has a melting point around 100 °C (with loss of water of hydration). The compound is stable under normal storage conditions and maintains its iron(II) oxidation state due to the stabilizing effect of the ammonium ion and sulfate matrix.
🧪 Applications
Ammonium iron(II) sulfate hexahydrate is widely used in analytical chemistry as a primary standard for the standardization of potassium permanganate solutions in redox titrations. It is also used in the preparation of other iron compounds, in teaching laboratories for oxidation-reduction experiments, and occasionally in photographic and dyeing processes. Its stability and predictable reactivity make it ideal for accurate quantitative analysis.
⚠️ Safety
Ammonium iron(II) sulfate hexahydrate should be handled with standard laboratory precautions. It may cause irritation to the skin, eyes, or respiratory tract if inhaled or ingested in dust form. Prolonged exposure to moisture and air can lead to slow oxidation of iron(II) to iron(III). Protective gloves and eye protection are recommended during handling. It should be stored in a tightly closed container in a cool, dry place away from oxidizing agents.
