TRISODIUM ORTHOPHOSPHATE (NA₃PO₄): THE HIGH-PURITY PHOSPHATE FOR PRECISION APPLICATIONS

Trisodium orthophosphate (TSP) is the fully neutralized sodium salt of orthophosphoric acid, distinct from other phosphates like pyrophosphates or metaphosphates. With its high alkalinity (pH ~12) and sequestering power, this compound is essential in industries requiring precise phosphate chemistry, from food processing to industrial water treatment.

Key Characteristics

Chemical Structure

• IUPAC Name: Trisodium phosphate
• Formula: Na₃PO₄ (anhydrous) or Na₃PO₄·xH₂O (hydrated forms)
• Molecular Weight: 163.94 g/mol (anhydrous)

Physical Properties

Grades & Purity

Specialized Applications

1. Food Industry (E339iii)

• Function:
  • Emulsifier: In processed cheeses (0.2–0.8%)
  • pH Regulator: Maintains acidity in cereals
  • Water Retention: Improves texture in meat products
• Advantage: More stable than lower phosphates (e.g., NaH₂PO₄) in high-pH systems

2. Precision Cleaning

• Mechanism:
  • Saponifies fats via hydrolysis (OH⁻ release)
  • Chelates Ca²⁺/Mg²⁺ ions (sequestration value: 13 mg CaCO₃/g)
• Uses:
  • Semiconductor wafer cleaning
  • Aerospace component degreasing

3. Water Treatment

• Corrosion Inhibition:
  • Forms protective iron phosphate films on pipes
  • Dosage: 5–20 ppm in cooling towers
• Scale Prevention:
  • Binds Ca²⁺ in boiler water (T < 150°C)

4. Chemical Synthesis

• Precursor for:
  • Sodium tripolyphosphate (STPP)
  • Calcium phosphate ceramics

Safety & Regulatory Status

⚠ Hazards:

• Skin/Eye Irritant: Causes burns (wear PPE)
• Environmental Impact:
  • Eutrophication risk (regulated in detergents)
  • Banned in EU household cleaners (Regulation (EC) No 648/2004)

✅ Handling:

• Store in sealed containers (hygroscopic)
• Neutralize spills with weak acids (e.g., citric acid)

Comparison to Other Phosphates

Market & Alternatives

• Price: $800–1,200/ton (food grade)
• Alternatives:
  • Sodium metasilicate (less eco-toxic)
  • Sodium carbonate (weaker alkali)