Disodium Hydrogen Phosphate (Disodium Hydrogen Phosphate, Na?HPO?)

1. Basic Chemical Information

- Chemical Formula: Na?HPO?  

- Systematic Name: Disodium phosphate  

- CAS Number:  

  - Anhydrous: 7558-79-4  

  - Dihydrate (Na?HPO?·2H?O): 10028-24-7  

  - Dodecahydrate (Na?HPO?·12H?O): 10039-32-4  

- Molar Mass:  

  - Anhydrous: 141.96 g/mol  

  - Dihydrate: 177.99 g/mol  

  - Dodecahydrate: 358.14 g/mol  

- Appearance: White crystals or powder, odorless, highly soluble in water, insoluble in ethanol.  

2. Physicochemical Properties

- Solubility:  

  - Solubility in water (20°C): ~7.7 g/100 mL (anhydrous), higher (hydrates).  

  - Insoluble in organic solvents such as ethanol.  

- pH (1% aqueous solution): 8.5~9.5 (weakly alkaline)  

- Thermal Stability: Decomposes above 200°C to form sodium pyrophosphate (Na?P?O?).  

3. Main Applications

(1) Food Industry

- Acidity Regulator: Used in dairy products, beverages, meat products, etc., to maintain stable pH.  

- Emulsifier: Improves texture in cheese and instant foods.  

- Nutritional Fortifier: Supplements phosphorus and sodium (intake must be controlled).  

(2) Biology and Medicine

- Buffer: Combined with Sodium Dihydrogen Phosphate (NaH?PO?)* to prepare PBS (Phosphate Buffered Saline), widely used in:  

  - Cell culture  

  - Protein purification  

  - Molecular biology experiments (e.g., PCR, electrophoresis)  

- Pharmaceutical Excipient: Used for pH adjustment in sustained-release tablets and injections.  

(3) Industrial Applications

- Water Treatment: Softens hard water and prevents boiler scaling.  

- Textile Dyeing: Used as an auxiliary agent to improve dye stability.  

- Ceramics and Electroplating: Used for surface treatment.  

(4) Other Uses

- Feed Additive (must comply with regulatory limits).  

- Flame Retardant Component (used in combination with nitrogen-containing compounds).  

4. Safety and Storage

- Toxicity: Low toxicity, but long-term excessive intake may cause hyperphosphatemia or sodium overload (must be limited in food).  

- Handling Protection: Avoid dust inhalation; wear gloves and goggles.  

- Storage Conditions:  

 - Store sealed and protect from moisture (hydrates are hygroscopic).  

 - Store separately from strong acids and oxidizers.