Disodium hydrogen phosphate is an inorganic compound with the chemical formula Na₂HPO₄. Its common forms are anhydrous and various hydrates (such as dihydrate Na₂HPO₄·2H₂O and dodecahydrate Na₂HPO₄·12H₂O).
Basic properties：
- Appearance: White crystals or powder, easily soluble in water, the aqueous solution is weakly alkaline.
- Solubility: easily soluble in water, insoluble in ethanol.
- pH value: The pH of 1% aqueous solution is about 9.
Main application：
- Food industry: used as quality improver, emulsifier, buffer, etc. for meat, cheese and other products.
- Medical field: used as buffer and laxative ingredient.
- Water treatment: used as water softener and corrosion inhibitor to prevent boiler scale.
- Laboratory: commonly used reagent for buffer solution preparation and chemical analysis.
- Others: also used in textile, papermaking, detergent and other industries.
Preparation method：
It is mainly produced by the reaction of phosphoric acid with sodium hydroxide or sodium carbonate. The reaction is as follows:
- H₃PO₄ + 2NaOH → Na₂HPO₄ + 2H₂O
- H₃PO₄ + Na₂CO₃ → Na₂HPO₄ + CO₂ + H₂O
Safety precautions：
- Inhalation: May irritate the respiratory tract, so please operate in a well-ventilated place.
- Contact: May irritate the skin and eyes, so please wear protective equipment when operating.
- Ingestion: Ingestion of large amounts may cause gastrointestinal discomfort, so please avoid accidental ingestion.
Storage：
It should be stored in a cool, dry, ventilated place, away from acids and flammable materials.
Summary：
Disodium hydrogen phosphate is widely used in food, medicine, water treatment and other fields. When using it, attention should be paid to safe operation and storage conditions.