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

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

PHOSPHORUS PENTOXIDE (P₂O₅ / P₄O₁₀)

Phosphorus Pentoxide / Phosphoric Pentoxide / Diphosphorus Pentoxide / Phosphorus(V) Oxide / Phosphoric Anhydride
CAS Number: 1314-56-3
EC Number: 215-236-1

1. IDENTIFICATION INFORMATION

2. PHYSICAL PROPERTIES

3. CHEMICAL PROPERTIES

Hydrolysis Reactions:

To Orthophosphoric Acid:

P₂O₅ + 3 H₂O → 2 H₃PO₄ (Orthophosphoric acid)

To Pyrophosphoric Acid:

P₂O₅ + 2 H₂O → H₄P₂O₇ (Pyrophosphoric acid)

To Metaphosphoric Acid:

P₂O₅ + H₂O → 2 HPO₃ (Metaphosphoric acid)

Production Reaction (White Phosphorus Combustion):

P₄ + 5 O₂ → 2 P₂O₅ (or P₄O₁₀)

Reaction with Alcohols (Esterification):

P₂O₅ + 6 ROH → 2 (RO)₃PO + 3 H₂O

4. PRODUCTION PROCESS

Reaction Equation:

P₄ (white phosphorus) + 5 O₂ → 2 P₂O₅ (or P₄O₁₀) + Heat (highly exothermic)

5. AVAILABLE FORMS AND SPECIFICATIONS

Typical Specifications:

6. APPLICATIONS

6.1. Phosphoric Acid Production – Largest Use

6.2. Fertilizer Industry

Fertilizer Note: P₂O₅ is the standard measure of phosphorus content in fertilizers. Plants require phosphorus for root development and flowering. Phosphorus deficiency causes stunted growth and dark green to reddish leaf tips. Excess phosphorus can reduce iron, zinc, and copper uptake.

6.3. Dehydrating and Drying Agent

Note: Phosphorus pentoxide is one of the strongest drying agents available. It can reduce water vapor concentration to less than 0.0001% (1 ppm) in gases.

6.4. Organic Synthesis

Dehydration Examples:

• Carboxylic acids → acid anhydrides

• Amides → nitriles

• Alcohols → alkenes

6.5. Laboratory Applications

6.6. Coatings, Varnishes and Polishes

6.7. Chemical Intermediate

6.8. Other Applications

7. PHOSPHORUS CONTENT IN FERTILIZERS

8. SAFETY AND HEALTH INFORMATION (GHS CLASSIFICATION)

Note: The GHS classification is based on the corrosive nature of phosphoric acid formed upon contact with moisture.

9. HAZARD STATEMENTS (H-CODES)

10. SAFETY STATEMENTS (P-CODES)

11. TOXICOLOGICAL INFORMATION

Health Effects:

12. FIRST AID MEASURES

13. FIRE FIGHTING MEASURES

14. ENVIRONMENTAL INFORMATION

15. STORAGE AND HANDLING

Handling Notes:

• Handle under dry inert atmosphere (nitrogen or argon) when possible

• Avoid generating dust

• Use only in well-ventilated areas (local exhaust)

• Do not allow contact with water or moisture

• Add small amounts to large volumes of water when making solutions (always add P₂O₅ to water, not water to P₂O₅)

• Wear full personal protective equipment

• Have emergency eyewash and safety shower available

16. TRANSPORT INFORMATION

17. REGULATORY INFORMATION

18. OTHER NAMES AND SYNONYMS

Database Identifiers:

19. IMPORTANT REACTIONS AND NOTES

Hydrolysis Sequence:

• With limited water: forms metaphosphoric acid (HPO₃) and pyrophosphoric acid (H₄P₂O₇)

• With excess water: forms orthophosphoric acid (H₃PO₄)

• The reaction is highly exothermic (large amount of heat released)

Dehydration Examples:

• Amides → Nitriles: RCONH₂ + P₂O₅ → RCN + H₂O

• Carboxylic acids → Acid anhydrides: 2 RCOOH + P₂O₅ → (RCO)₂O + H₂O

• Alcohols → Alkenes: ROH + P₂O₅ → R' (alkene) + H₂O

Drying Efficiency:

• P₂O₅ reduces water vapor concentration to <0.0001% (1 ppm) in gases

• One of the most effective desiccants available

• More powerful than silica gel, molecular sieves, calcium chloride, and calcium sulfate

20. SUMMARY AND IMPORTANT WARNINGS

SUMMARY:

Phosphorus pentoxide (P₂O₅ / P₄O₁₀, CAS 1314-56-3) is a white, odorless, crystalline powder that is one of the strongest drying agents known. It has a density of 2.39 g/cm³ at 20°C, melts at 340°C, and sublimes at 360°C. P₂O₅ is the anhydride of phosphoric acid and reacts violently and exothermically with water to form orthophosphoric acid (H₃PO₄), pyrophosphoric acid (H₄P₂O₇), or metaphosphoric acid (HPO₃), depending on water quantity. It is produced by burning white phosphorus in excess oxygen (P₄ + 5 O₂ → 2 P₂O₅). The largest application is the production of phosphoric acid, followed by fertilizer production (as the standard measure of phosphorus content in fertilizers such as DAP - diammonium phosphate). Other major applications include use as a powerful dehydrating agent (drying gases and organic solvents), in organic synthesis (dehydration reactions, esterification, cyclization), as a laboratory desiccant, and in the production of phosphate esters, flame retardants, and coatings/varnishes.

Key Properties:

Main Application Areas:

Key Safety Points:

• CORROSIVE: Causes severe skin burns and eye damage (H314)

• WATER REACTION: Reacts violently with water - generates heat and forms corrosive phosphoric acid

• DUST HAZARD: Avoid breathing dust (corrosive to respiratory tract)

• HANDLING: Always add phosphorus pentoxide to water (never water to P₂O₅) when making solutions

• PROTECT FROM MOISTURE: Store in tightly closed, moisture-proof containers

• USE PPE: Chemical goggles, face shield, acid-resistant gloves (neoprene, nitrile, butyl rubber), protective clothing

• USE VENTILATION: Use in well-ventilated area or under fume hood

• STORAGE: Store in cool, dry place; under dry inert gas (N₂, Ar) if possible

• INCOMPATIBLES: Water, alcohols, bases, combustible materials

IMPORTANT WARNINGS:

Violent Water Reaction: Phosphorus pentoxide reacts violently and exothermically with water to form phosphoric acid. The reaction is highly exothermic and can cause splattering of hot acid. NEVER add water to phosphorus pentoxide. ALWAYS add phosphorus pentoxide slowly to a large volume of water with stirring and cooling. The reaction produces orthophosphoric acid (H₃PO₄), pyrophosphoric acid (H₄P₂O₇), or metaphosphoric acid (HPO₃) depending on water quantity.

Extreme Hygroscopicity: P₂O₅ is extremely hygroscopic and will aggressively absorb moisture from the air, converting to sticky phosphoric acid. It is one of the most powerful drying agents available, capable of reducing water vapor concentration in gases to less than 0.0001% (1 ppm). Containers must be kept tightly sealed and opened only in dry environments. Ideally, handle under dry inert gas (nitrogen or argon).

Corrosive Hazard: The phosphoric acid formed upon contact with moisture causes severe skin burns and eye damage (H314). Contact with skin or eyes causes immediate chemical burns. Inhalation of dust causes severe respiratory tract irritation. Always wear appropriate personal protective equipment including chemical goggles, face shield, acid-resistant gloves (neoprene, nitrile, butyl rubber), and acid-resistant protective clothing. Work under fume hood or with adequate local exhaust ventilation.

Fertilizer Applications: P₂O₅ is the standard measure of phosphorus content in fertilizers. The highest phosphorus content fertilizer is DAP (diammonium phosphate) with 46% P₂O₅ (18-46-0). Phosphorus is essential for plant root development and flowering. Phosphorus deficiency causes stunted growth and dark green to reddish-purple leaf tips. Excess phosphorus can inhibit iron, zinc, and copper uptake, potentially reducing crop yields. The N-P-K ratio represents nitrogen (N), phosphorus (as P₂O₅), and potassium (as K₂O) percentages.

Drying Applications: P₂O₅ is used as an extremely powerful desiccant for drying gases and organic solvents. It is more effective than calcium chloride, silica gel, molecular sieves, and calcium sulfate. It is commonly used in laboratory desiccators and industrial gas drying systems. However, it cannot be used for drying materials that are reactive with phosphoric acid (e.g., bases, alcohols, many organic compounds).

Organic Synthesis Dehydration: In organic synthesis, P₂O₅ is a powerful dehydration agent used to convert:

• Amides to nitriles (RCONH₂ → RCN)

• Carboxylic acids to acid anhydrides (2 RCOOH → (RCO)₂O)

• Alcohols to alkenes (ROH → alkene)

• Oximes to amides (Beckmann rearrangement)
  It is also used in cyclization reactions and condensation reactions.

Phosphoric Acid Production: The largest industrial use of P₂O₅ is the production of phosphoric acid (H₃PO₄) by controlled hydrolysis. Phosphoric acid is used in fertilizers (as ammonium phosphates), food additive (E338), water treatment (defluoridation), metal treatment (phosphating), and production of phosphate esters.

Storage Requirements: Store in tightly closed, moisture-proof containers (glass, plastic-coated steel, HDPE) in a cool, dry, well-ventilated area. Avoid storage near water sources or high humidity areas. For long-term storage, seal containers under dry inert gas (nitrogen or argon). Shelf life is 12-24 months when stored properly.

First Aid - Immediate Action: For skin contact, remove contaminated clothing immediately and wash with large amounts of water for at least 15 minutes. Do not attempt to neutralize with bases. For eye contact, flush immediately with water for 15-20 minutes. Seek immediate medical attention for all significant exposures. For inhalation, move to fresh air; give oxygen if breathing difficulty. For ingestion, do not induce vomiting; seek immediate medical attention.

Incompatibilities: P₂O₅ is incompatible with water (violent reaction), alcohols (esterification with heat release), bases (neutralization), and combustible materials (may ignite if moisture is present). It should be stored away from these materials.

Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS) provided by the manufacturer/supplier. Phosphorus pentoxide is a corrosive material that reacts violently with water. Always wear appropriate personal protective equipment. Handle under dry conditions away from moisture. Never add water to phosphorus pentoxide; always add phosphorus pentoxide slowly to water. In case of fire or spill, follow emergency procedures. Seek immediate medical attention for significant exposures.