Phosphoric Acid (H₃PO₄)
High-purity industrial and food-grade inorganic acid
Overview
Phosphoric Acid (CAS No: 7664-38-2), also known as orthophosphoric acid, is a colorless, odorless, viscous liquid or crystalline solid inorganic acid. Known as food additive E338, it is widely used in various industrial applications.
Phosphoric acid is utilized in fertilizer production, food and beverage industries, detergent manufacturing, metal cleaning, and rust inhibition. It also finds applications in pharmaceuticals and dentistry.
Applications
Phosphoric Acid has a wide range of industrial and commercial applications:
Fertilizer Production
Used as a primary raw material for phosphate fertilizers.
Food Industry
Acts as an acidity regulator (E338) in soft drinks and other foods.
Metal Processing
Used for cleaning metal surfaces and rust inhibition.
Detergents
Serves as a water softener in laundry and dishwashing detergents.
Pharmaceuticals
Used in dental products and certain drug formulations.
Corrosion Inhibitors
Used in water systems to prevent corrosion.
Technical Specifications
| Property | Value | Unit | Test Method |
|---|---|---|---|
| Chemical Formula | H₃PO₄ | - | - |
| CAS Number | 7664-38-2 | - | - |
| EC Number | 231-633-2 | - | - |
| Molecular Weight | 98.00 | g/mol | - |
| Appearance | Colorless, transparent liquid or crystalline solid | - | Visual |
| Odor | Odorless | - | Olfactometry |
| Density (20°C, 85%) | 1.685 | g/cm³ | ASTM D4052 |
| Melting Point (100%) | 42.35 | °C | ASTM D1015 |
| Boiling Point (85%) | 158 | °C | ASTM D1078 |
| pH Value (1% solution) | 1.5 | - | ASTM E70 |
| Viscosity (20°C, 85%) | 47 | cP | ASTM D445 |
| Solubility in Water | Fully miscible | - | - |
| Purity | ≥85.0 | % | ASTM E611 |
| Heavy Metal Content (Pb) | ≤5 | ppm | ASTM E1613 |
| Sulfate Content | ≤0.005 | % | ASTM D516 |
| Chloride Content | ≤0.0005 | % | ASTM D512 |
Safety Information
Hazard Symbols and Statements
Corrosive Health Hazard Environmental Hazard
Personal Protective Equipment (PPE)
- Acid-resistant gloves (neoprene, nitrile, or PVC)
- Chemical safety goggles or face shield
- Respiratory protection against acid vapors
- Acid-resistant apron or work clothing
- Chemical-resistant shoes or boots
Storage Conditions
- Store in a cool, dry, well-ventilated area
- Use stainless steel, polyethylene, or glass containers
- Storage temperature: 15-30°C
- Keep away from bases and metals
- Protect from moisture
Firefighting Measures
- Non-flammable, but may cause fire when in contact with flammable materials
- Suitable extinguishers: Water mist, dry chemical
- Trained personnel should use appropriate respiratory protection
- Combustion products may be toxic (phosphorus oxides)
Handling and Storage
Handling
- Ensure containers are tightly closed
- Avoid eating, drinking, or smoking during handling
- Provide adequate ventilation in transport vehicles
- Keep neutralizing materials available for spills
- Avoid contact with metal surfaces
Storage
- Store in stainless steel, polyethylene, or glass containers
- Ensure proper signage in storage areas
- Use appropriate breather valves in storage tanks
- Provide secondary containment for large quantities
- Keep acid neutralization kits in storage areas
Spill Response Measures
- Evacuate exposed personnel from the area
- Use appropriate personal protective equipment
- Contain spills with sand, sodium bicarbonate, or other neutralizing materials
- Dispose of absorbed material properly
- Rinse the spilled area thoroughly with water
Regulatory Information
GHS Classification
- Skin Corrosion/Irritation Category 1A
- Serious Eye Damage/Eye Irritation Category 1
- Acute Toxicity (Oral) Category 3
- Specific Target Organ Toxicity (Single Exposure) Category 3
Key Regulations
- REACH: Registered
- CLP: Compliant
- OSHA: Subject to hazard communication standard
- NFPA 704: Health 3, Flammability 0, Reactivity 0
- Food Codex: Approved as E338
Food Compliance Certifications
- FCC (Food Chemicals Codex) compliant
- Kosher certified (optional)
- Halal certified (optional)
- Non-GMO
Environmental Information
Environmental Impact
Phosphoric acid can exhibit high toxicity in aquatic environments and cause pH reduction. It may lead to phosphate accumulation in soil. It is biodegradable but can have environmental impacts at high concentrations.
Biodegradation
- Water: Degraded by microbial activity
- Soil: Assimilated as phosphate through microbial activity
- Atmosphere: Does not undergo photochemical reactions
Waste Management
- Classified as hazardous waste
- Neutralize before disposal at licensed facilities
- Do not discharge into sewers or surface waters
- Dispose of in accordance with local regulations
Frequently Asked Questions
How is phosphoric acid produced?
Phosphoric acid is produced via two main methods: the wet process (reaction of phosphate rocks with sulfuric acid) and the thermal process (burning elemental phosphorus and hydration). The wet process is typically used for industrial applications.
What is the difference between food-grade and industrial phosphoric acid?
Food-grade phosphoric acid is produced with higher purity and lower heavy metal content. Industrial-grade may contain more impurities and is not suitable for food applications.
How does phosphoric acid differ from other acids?
Phosphoric acid is a triprotic acid (can donate three protons) and is less corrosive than sulfuric or hydrochloric acid. It also serves as a phosphate ion source for specific applications.
What should I do if phosphoric acid contacts skin?
Remove contaminated clothing immediately and rinse the skin with plenty of water for at least 15 minutes. Seek medical attention if irritation persists. For eye contact, rinse eyes with water for at least 15 minutes and seek immediate medical help.
How is phosphoric acid diluted?
Always add acid to water, never water to acid. Add slowly while stirring and monitor heat generation. Use appropriate personal protective equipment during dilution.