Phosphorus Pentoxide, Phosphoric Pentoxide, Diphosphorus Pentoxide, 1314-56-3

Phosphorus Pentoxide, Phosphoric Pentoxide, Diphosphorus Pentoxide, 1314-56-3

Phosphorus Pentoxide (P₂O₅ / P₄O₁₀)

Chemical Identity

• CAS No: 1314-56-3

• EINECS No: 215-236-1

• Chemical Formula: P₄O₁₀

• Molecular Weight: 220.02 g/mol

• Synonyms: Phosphorus(V) oxide, Phosphoric anhydride, Diphosphorus pentoxide

Physical Properties

• Appearance: White crystalline powder

• Density: 2.39 g/cm³ (20°C)

• Melting Point: 340°C

• Boiling Point: 360°C (sublimes)

• Odor: Odorless

• Refractive Index: 1.435 (20°C)

• Solubility: Reacts with water to form phosphoric acids (H₃PO₄, H₄P₂O₇, HPO₃)

Chemical Properties

• Reactivity: Vigorous reaction with water, forming different phosphoric acids depending on hydration level:

  • P₂O₅ + 3H₂O → 2H₃PO₄ (Orthophosphoric acid)

  • P₂O₅ + 2H₂O → H₄P₂O₇ (Pyrophosphoric acid)

  • P₂O₅ + H₂O → 2HPO₃ (Metaphosphoric acid)

• Hygroscopic: Strong moisture absorber.

• Function: Powerful dehydrating and drying agent.

Production

Phosphorus pentoxide is obtained by burning elemental white phosphorus in excess oxygen:

P4+5O2→2P2O5

Applications

• Phosphoric Acid Production – Key intermediate in industrial processes.

• Organic Synthesis – Used as a dehydrating agent, especially in conversion of amides to nitriles.

• Drying Agent – Removes water from solvents and gases.

• Surface Treatments – Additive in polishes and varnishes.

• Agriculture – Source of phosphorus in fertilizers, enhancing root development and flowering.

Agricultural Use

• Improves root growth and promotes flowering.

• Phosphorus deficiency symptoms in plants: stunted growth, dark green leaves turning reddish-purple, leaf curling.

• Excess phosphorus can reduce uptake of iron (Fe), zinc (Zn), and copper (Cu), lowering yield.

• Fertilizer with highest phosphorus content: DAP (Diammonium Phosphate, 18-46-0).

Safety & Handling

• Hazards: Irritates respiratory tract if inhaled; harmful to eyes and skin upon contact.

• Precautions: Use protective gloves, goggles, and masks.

• Storage: Keep in tightly sealed containers, away from moisture and humidity.