Potassium dihydrogen phosphate

Potassium Dihydrogen Phosphate (KH₂PO₄)

1. Basic Properties

- Chemical Formula: KH₂PO₄  

- Appearance: Colorless or white crystalline powder, easily soluble in water, aqueous solution is weakly acidic (pH ≈ 4.4–4.7).  

- Molecular Weight: 136.09 g/mol  

- Melting Point: 252.6°C (decomposes)  

- Density: 2.34 g/cm³  

2. Chemical Characteristics

- Buffering Effect: KH₂PO₄ is a common buffer agent, forming phosphate buffer solution (PBS) with K₂HPO₄, used to adjust pH (range 5.8–8.0).  

- Thermal Decomposition: Decomposes into potassium metaphosphate (KPO₃) and water when heated above 400°C: 

3. Main Applications

- Agriculture:  

  - High-purity fertilizer (phosphorus-potassium compound fertilizer, promotes flowering and fruiting).  

  - Foliar fertilizer or drip irrigation fertilization (easily absorbed, suitable for phosphorus-deficient soils).  

- Food Industry:  

  - Food additive (used as acidity regulator, leavening agent).  

- Laboratory:  

  - Preparation of buffer solutions.  

  - Standard reagent for flame photometry to measure potassium.  

- Other Fields:  

  - Pharmaceuticals (electrolyte supplement).  

  - Auxiliary agent in ceramics and dye industries.  

4. Safety and Storage

- Toxicity: Low toxicity, but excessive intake may cause electrolyte imbalance.  

- Storage: Seal to prevent moisture, avoid contact with strong bases.