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Views: 0 Author: Site Editor Publish Time: 2026-08-07 Origin: Site
What Is Sodium Dihydrogen Phosphate (NaH₂PO₄)?
Sodium Dihydrogen Phosphate — also widely known as Monosodium Phosphate (MSP), Monobasic Sodium Phosphate, or Sodium Phosphate Monobasic — is an inorganic compound with the chemical formula NaH₂PO₄. It is one of the most versatile phosphate salts in industrial chemistry, serving critical functions across water treatment, metal finishing, detergent manufacturing, food processing, and animal nutrition.
1. Chemical Identity at a Glance
Property | Value |
IUPAC Name | Sodium dihydrogen phosphate |
Common Synonyms | Monosodium Phosphate (MSP), Monobasic Sodium Phosphate, Sodium Phosphate Monobasic, Sodium Biphosphate |
Chemical Formula (Anhydrous) | NaH₂PO₄ |
Molecular Weight (Anhydrous) | 119.98 g/mol |
CAS Number | 7558-80-7 (Anhydrous); 10049-21-5 (Monohydrate); 13472-35-0 (Dihydrate) |
E Number (Food Grade) | E339(i) |
Appearance | White crystalline powder or granular solid |
Solubility | Highly soluble in water (~85 g/100 mL at 25 °C); insoluble in ethanol |
pH (1% aqueous solution) | 4.2–4.6 (mildly acidic) |
P₂O₅ Content | 56–59% (anhydrous basis) |
Melting Point | Decomposes above 190 °C, losing water of crystallization |
HS Code | 2835.22 |
2. Hydrate Forms: Anhydrous, Monohydrate, and Dihydrate
Sodium Dihydrogen Phosphate is commercially available in three hydrate states. Each has subtle differences in molecular weight, phosphorus content, and application suitability:
Hydrate Form | Molecular Formula | Molecular Weight | P₂O₅ Content | Typical Use Cases |
Anhydrous | NaH₂PO₄ | 119.98 | ~59% | High-concentration formulations, dry blends requiring minimal moisture |
Monohydrate | NaH₂PO₄·H₂O | 138.00 | ~51% | General industrial, food processing, standard-grade applications |
Dihydrate | NaH₂PO₄·2H₂O | 156.01 | ~45% | Laboratory buffers, metal treatment baths, aqueous formulations |
Frequently Asked Questions (FAQ)
Q: What is the difference between Sodium Dihydrogen Phosphate and Monosodium Phosphate?
A: They are the same compound. "Monosodium Phosphate" (MSP) is the common commercial name, while "Sodium Dihydrogen Phosphate" is the systematic IUPAC name. Both refer to NaH₂PO₄.
Q: Is Sodium Dihydrogen Phosphate acidic or alkaline?
A: Acidic. A 1% aqueous solution has a pH of approximately 4.2–4.6. This distinguishes MSP from its disodium and trisodium counterparts, which are alkaline.
Q: Can Sodium Dihydrogen Phosphate be used in food?
A: Yes. Food-grade MSP is designated as E339(i) in the EU and is Generally Recognized As Safe (GRAS) by the US FDA (21 CFR 182.1778). It is widely used as an acidity regulator, emulsifying salt, and sequestrant in processed foods.
Q: What is the shelf life of Sodium Dihydrogen Phosphate?
A: 24 months from the date of manufacture when stored in original sealed packaging in a cool, dry environment.
Q: Is MSP hygroscopic?
A: Yes. The anhydrous form readily absorbs moisture from the air. Always reseal opened containers immediately and store in low-humidity conditions.
Q: How is Sodium Dihydrogen Phosphate shipped internationally?
A: MSP is classified as a non-hazardous chemical. It is typically shipped in 20-foot containers (FCL), with a loading capacity of approximately 20–27 metric tons depending on packaging type and local weight regulations. Standard shipping documents include a commercial invoice, packing list, bill of lading, COA, and MSDS.
Q: What is the minimum order quantity (MOQ)?
A: Most manufacturers set MOQs at 1–5 metric tons for trial orders. For regular procurement, typical order quantities range from one FCL (20–27 MT) to multiple containers per shipment.
Q: How does MSP compare to Phosphoric Acid for metal treatment?
A: MSP offers a milder, more controlled acidic environment than liquid phosphoric acid (H₃PO₄), making it the preferred choice for precision phosphating processes where over-etching must be avoided. MSP is also safer to handle and easier to ship as a dry powder.
Summary
Sodium Dihydrogen Phosphate (NaH₂PO₄ / MSP) is a workhorse phosphate salt with a unique combination of properties — acidic pH, high water solubility, excellent buffering capacity, and strong metal-chelating ability. These characteristics make it indispensable across:
Industrial manufacturing:
● Water treatment, metal phosphating, electroplating, detergent formulation
Food processing:
● pH control, emulsification, shelf-life extension
Animal nutrition:
● Bioavailable phosphorus and sodium supplementation in feed
Emerging applications:
● Battery material synthesis, advanced ceramics
