Phosphoric Acid

Classification

Classification shown is for concentrated (about 75–85%) solutions; weaker solutions carry fewer hazards. Corrosive to metals, Category 1; Acute toxicity (oral), Category 4; Skin corrosion, Category 1B; Serious eye damage, Category 1

Hazard statements

• H290 May be corrosive to metals.
• H302 Harmful if swallowed.
• H314 Causes severe skin burns and eye damage.

Key precautionary statements

• P234 Keep only in original packaging.
• P264 Wash hands thoroughly after handling.
• P270 Do not eat, drink or smoke when using this product.
• P280 Wear protective gloves, protective clothing, eye protection and face protection.
• P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
• P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
• P305+P351+P338+P310 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. Immediately call a POISON CENTER or doctor.
• P405 Store locked up.

The OSHA permissible exposure limit in Table Z-1 is 1 mg/m³ as an 8-hour TWA. NIOSH recommends 1 mg/m³ as a 10-hour TWA plus a 3 mg/m³ short-term limit, and the ACGIH TLV and Cal/OSHA PEL both pair 1 mg/m³ TWA with a 3 mg/m³ STEL. The NIOSH IDLH is 1,000 mg/m³. Phosphoric acid has very low vapor pressure, so airborne exposure comes mostly from mists created by spraying, heating, mixing or splashing. No skin notation is assigned, but concentrated solutions burn on contact. NIOSH advises an eyewash and quick drench shower wherever solutions stronger than 1.6% are handled. State OSHA plans may set different limits.

• Appearance: Thick, colorless crystalline solid when pure; usually handled as a clear, syrupy water solution (commonly 75–85%)
• Odor: Odorless
• Molecular weight: 98.0
• Boiling point: 415°F (213°C)
• Melting point: 108°F (42°C)
• Flash point: Not applicable (noncombustible)
• Explosive limits: Not applicable
• Vapor pressure: 0.03 mmHg
• Specific gravity: 1.87 (pure); 1.33 (50% solution)
• Water solubility: Miscible

Inhalation

Mist irritates the nose, throat and upper airways, causing coughing and wheezing.

Skin

Concentrated solutions cause chemical burns. Repeated contact with weaker solutions can dry and crack the skin and cause dermatitis.

Eyes

Causes irritation and burns that can permanently damage the eyes.

Ingestion

Harmful if swallowed. Concentrated acid burns the mouth, throat and stomach. Get medical attention immediately.

Target organs

Eyes, skin, respiratory system

Long-term effects

Repeated exposure to mist may cause bronchitis, with cough, phlegm and shortness of breath. The New Jersey Department of Health notes it has not been tested for cancer or reproductive effects in animals.

Gloves

The New Jersey Department of Health lists natural rubber, nitrile, neoprene, polyvinyl chloride (PVC) and Viton. It gives no breakthrough times, so check the glove maker's data for your concentration.

Eyes and face

Indirect-vent, splash-resistant chemical goggles, plus a face shield over the goggles when handling concentrated acid. NJDOH advises against wearing contact lenses.

Respiratory

Not normally needed where mist is controlled. Above exposure limits, NIOSH lists a full-facepiece respirator with N100, R100 or P100 filters, or supplied-air options, up to 50 mg/m³. Use a pressure-demand SCBA for emergencies or unknown concentrations.

Clothing

Acid-resistant apron, sleeves and boots for transfers. Remove clothing promptly if wet or contaminated, and keep an eyewash and quick drench shower within reach.

Store in tightly closed, acid-resistant containers in a cool, well-ventilated corrosives area. The acid corrodes most metals and releases flammable hydrogen gas as it does, and it can attack some rubbers, plastics and coatings.

When diluting, add the acid slowly to water while stirring, never water to the acid, because mixing releases heat. Wash hands after handling.

Keep away from

• Bleach (sodium hypochlorite) and ammonia; NIOSH warns never to mix phosphoric acid with solutions containing either
• Strong bases such as sodium hydroxide and potassium hydroxide
• Most metals, especially finely powdered metals (release flammable hydrogen gas)
• Nitromethane
• Combustibles, alcohols, amines and epoxides

• Evacuate the area and keep unprotected people away.
• Wear acid-resistant gloves, goggles, face shield and protective clothing.
• Cover liquid spills with dry lime, sand or soda ash, then collect into covered containers for disposal.
• Ventilate and wash the area after cleanup is complete.
• Keep out of drains, sewers and waterways; the waste may need to be handled as hazardous waste.
• For larger incidents, refer to ERG Guide 154.

Suitable extinguishing media

• Use the agent best suited to the surrounding fire (phosphoric acid does not burn)
• Water spray to cool fire-exposed containers

Special hazards

Noncombustible, but contact with metals can produce flammable hydrogen gas that may collect in closed spaces. Fires produce toxic phosphorus oxides. Firefighters should wear SCBA and full protective gear.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical; labels, safety data sheets and worker training required.
• OSHA Air Contaminants (29 CFR 1910.1000 Table Z-1): PEL 1 mg/m³ TWA.
• CERCLA hazardous substance (40 CFR 302.4): Reportable quantity 5,000 lb (2,270 kg).
• EPCRA Section 302 (40 CFR 355): Not listed as an extremely hazardous substance.
• EPCRA Section 313 / TRI (40 CFR 372.65): Removed from the list in 2000; 1999 was the last reporting year.
• DOT Hazardous Materials (49 CFR 172.101): UN1805 Phosphoric acid, solution, Class 8, PG III. The solid ships as UN3453.

• NIOSH Pocket Guide: Phosphoric acid
• OSHA Occupational Chemical Database: Phosphoric acid
• NJ Department of Health Hazardous Substance Fact Sheet: Phosphoric acid
• Sigma-Aldrich SDS: Phosphoric acid, 85 wt.% (product 345245)
• 40 CFR 302.4: CERCLA hazardous substances and reportable quantities
• EPA final rule deleting phosphoric acid from the EPCRA 313 list (2000)