Ammonium Molybdate

Ammonium molybdate, specifically ammonium heptamolybdate tetrahydrate, is a widely used inorganic compound with diverse applications. Here's a more detailed description:

Chemical Properties and Structure:

• Chemical Formula: (NH₄)₆Mo₇O₂₄·4H₂O (the tetrahydrate form is the most common)
• Composition: Consists of ammonium cations (NH₄⁺) and heptamolybdate anions (Mo₇O₂₄⁶⁻), along with water molecules of hydration.
• Appearance: Typically appears as white or slightly yellowish-green crystalline powder or crystals.
• Solubility: Soluble in water, though solubility decreases in solutions with high ammonium ion concentrations.
• Decomposition: Upon heating, it decomposes, releasing ammonia (NH₃), water (H₂O), and molybdenum trioxide (MoO₃). This decomposition process is utilized in certain analytical procedures.
• The thermal decomposition process is quite complex and various polymolybdates are made as intermediates during the decomposition.

Physical Properties:

• It is a crystalline solid.
• It is odorless.
• Its density varies slightly, dependent on it's precise hydration, but is within the 2.4 - 2.5 g/cm³ range.

Uses and Applications:

• Chemical Analysis:
  • A crucial reagent in analytical chemistry, particularly for the determination of phosphate, silicate, arsenate, and lead.
  • Used in the detection and quantification of these ions through the formation of heteropoly acids.
• Fertilizer:
  • Serves as a source of molybdenum, an essential micronutrient for plants.
• Catalyst:
  • Used as a catalyst in various industrial processes.
• Metal Finishing:
  • Used in metal finishing processes.
• Laboratory Reagent:
  • Used in many different lab situations.

Hazards:

• Irritant: Can irritate the skin, eyes, and respiratory tract.
• Ingestion: May cause gastrointestinal discomfort if ingested.
• Environmental Concerns: Molybdenum compounds can have environmental impacts, especially in high concentrations.
• When heated, it can release irritating and toxic fumes.

Important Considerations:

• Proper handling procedures, including the use of appropriate personal protective equipment (PPE) and adequate ventilation, are essential.
• Care should be taken when disposing of ammonium molybdate, in accordance with local regulations.