CAS 7664-38-2 · Triprotic Mineral Acid
Phosphoric Acid
H₃PO₄ · MW 97.99 g/mol · Orthophosphoric Acid
A medium-strength triprotic mineral acid with three ionizable protons and a wide range of industrial, food, and specialty applications. Unlike the strong mineral acids, phosphoric acid's moderate acidity and non-oxidizing nature make it suitable for food contact, dental, and water treatment uses. Texas-Chem supplies H₃PO₄ in 75%, 85% technical, and 85% food grades.
Formula
H₃PO₄
Flash Point
Non-flammable
pKa₁
2.15
Pack Sizes
Drums · Totes · Bulk
Structural Formula
Triprotic acid — central phosphorus with one P=O and three P–OH bonds
Safety & Regulatory
- NFPA Health
- 3 — Serious hazard
- NFPA Flammability
- 0 — Non-flammable
- NFPA Reactivity
- 0 — Stable
- OSHA PEL (TWA)
- 1 mg/m³
- ACGIH TLV-TWA
- 1 mg/m³
- ACGIH TLV-STEL
- 3 mg/m³
- DOT Hazard Class
- 8 — Corrosive
- UN Number
- UN 1805
Corrosive — use acid-resistant PPE. Food/dental applications require food-grade certification. SDS available upon request.
Grades & Packaging
Available Grades
Pack Sizes
Physical & Chemical Properties
| Molecular Formula | H₃PO₄ |
| Molecular Weight | 97.99 g/mol |
| CAS Number | 7664-38-2 |
| Boiling Point | 158 °C (decomposes) |
| Melting Point | 42.4 °C (pure) |
| Flash Point | Non-flammable |
| Density | 1.685 g/cm³ (85% solution) |
| Vapor Pressure | Negligible at 20 °C |
| Solubility | Miscible with water in all proportions |
| pKa₁ | 2.15 |
| pKa₂ | 7.20 |
| pKa₃ | 12.35 |
Industrial Applications
Fertilizer Production
The largest use of phosphoric acid — feedstock for monoammonium phosphate (MAP), diammonium phosphate (DAP), and triple superphosphate (TSP) fertilizers. Wet-process phosphoric acid is the standard grade for fertilizer applications.
Food & Beverage Acidulant
Food-grade phosphoric acid (E338) is the acidulant in cola beverages, providing characteristic tartness. Also used in jams, cheeses, and processed meats as a pH adjuster and preservative.
Metal Surface Treatment
Rust converter and phosphating agent — phosphoric acid reacts with iron oxide to form iron phosphate, converting rust to a stable, paintable surface. Used in automotive, aerospace, and industrial coating pretreatment.
Semiconductor & Electronics
Etchant for silicon nitride and aluminum in semiconductor fabrication. High-purity phosphoric acid is used in wet etching processes for microelectronics manufacturing.
Dental & Pharmaceutical
Dental etching agent for bonding procedures — 35–37% phosphoric acid etches enamel to improve adhesive bonding. Also used as a pH adjuster and buffering agent in pharmaceutical formulations.
Water Treatment
Corrosion inhibitor in potable water systems — low doses of phosphoric acid form a protective phosphate film on pipe surfaces, reducing lead and copper leaching. Also used for pH adjustment in boiler water treatment.
Why Source Phosphoric Acid from Texas-Chem?
- 35+ years supplying industrial acids to Texas manufacturers
- 75%, 85% technical, and 85% food grades available
- Drums, totes, and bulk tanker delivery
- Competitive pricing backed by top-tier producer relationships
- Technical support and SDS documentation with every order
- Same-day quotes for standard quantities