Food grade Industrial grade 98% Sodium Phosphate Monobasic Monohydrate CAS 10049-21-5

What is Sodium Phosphate Monobasic Monohydrate? How does it work? What are its industrial applications?

I. What are Sodium Phosphate Monobasic Monohydrate? How do they work?

Sodium phosphate monobasic monohydrate, also known as sodium dihydrogen phosphate monohydrate, is a hydrate of sodium dihydrogen phosphate with one molecule of water of crystallization. Its molecular formula is NaH₂PO₄·H₂O, and its CAS number is 10049-21-5. It is a white crystalline powder, readily soluble in water, and its aqueous solution is weakly acidic (pH approximately 4.1-4.5 for a 1% solution). In industrial applications, it is an important water treatment agent, metal surface treatment agent, and buffer—used in boiler water treatment, circulating cooling water treatment, and metal phosphating for rust prevention. It is also widely used as an electroplating buffer, detergent cleaning aid, pH adjuster in papermaking and textile printing and dyeing, and a raw material in chemical synthesis.

Basic information : Chinese name: Sodium dihydrogen phosphate monohydrate; English name: Sodium Phosphate Monobasic Monohydrate (also known as sodium dihydrogen phosphate monohydrate, sodium dihydrogen phosphate monohydrate, abbreviated MSP); CAS number: 10049-21-5; Molecular formula: NaH2PO4·H2O; Molecular weight: approximately 137.99; Appearance: white crystalline powder or granules; Easily soluble in water, insoluble in ethanol, ether, and chloroform; Aqueous solution is weakly acidic (pH of 1% aqueous solution at 25℃ is approximately 4.1-4.5); Density: approximately 2.04 g/cm³; Melting point: approximately 100℃ (after removal of water of crystallization); Odorless, hygroscopic; Industrial grade is mainly used for water treatment, metal processing, and chemical applications.

Structurally , sodium dihydrogen phosphate monohydrate consists of a sodium ion, a dihydrogen phosphate ion, and a water of crystallization molecule. The phosphorus atom is at the center, forming a tetrahedron with four oxygen atoms. Two hydroxyl groups, an oxygen anion, and a double oxygen bond are connected. The dihydrogen phosphate ion carries a negative charge and is ionicly bonded to the sodium ion. The water molecule enters the crystal lattice as water of crystallization. The dihydrogen phosphate ion (H₂PO₄⁻) can further dissociate into hydrogen ions and can exchange with hydrogen phosphate ions, giving it the functions of a weak acid, buffer, coordination, and phosphorus source—this is the structural basis for its role in water treatment, metal processing, and chemical industries.

Physically , sodium dihydrogen phosphate monohydrate is a white crystalline powder or granules; it is readily soluble in water, but insoluble in ethanol, ether, and chloroform; its aqueous solution is weakly acidic (pH approximately 4.1-4.5); its density is approximately 2.04 g/cm³; its melting point is approximately 100℃ (after removing the water of crystallization); it is odorless and hygroscopic; it needs to be stored in a sealed, dry, and cool place.

Chemically , sodium dihydrogen phosphate monohydrate is an acidic salt: it dissociates into dihydrogen phosphate ions and hydrogen ions in water, making the aqueous solution weakly acidic; dihydrogen phosphate and hydrogen phosphate ions form a buffer pair, providing pH buffering capacity; phosphate ions can coordinate with metal ions such as calcium, magnesium, and iron, inhibiting scale growth; phosphate ions can also react with metal surfaces to form a phosphate conversion film; and it loses its water of crystallization and further water loss upon heating.

Why do sodium phosphate, monobasic, and monohydrate play these roles in industries such as water treatment, metal processing, daily chemicals, papermaking, textiles, and chemicals? Their mechanisms of action are mainly as follows:

Phosphate coordination scale inhibition mechanism : Phosphate groups coordinate with calcium and magnesium ions in water, interfering with the nucleation and growth of scale crystals—the basis of scale inhibition in boiler water and circulating water.

Acidic salt buffering mechanism : Dihydrogen phosphate and hydrogen phosphate form a buffer pair to maintain the pH of process systems such as electroplating solutions, pulp and dye baths—the basis of industrial process control.

Phosphating film formation mechanism : Phosphate ions react with the metal surface to form an insoluble phosphate conversion film, which improves corrosion resistance and coating adhesion—the basis of metal phosphating for rust prevention.

Adsorption and dispersion mechanism : Phosphate ions are adsorbed and dispersed on the surface of particles, fibers and dirt, preventing redeposition—the basis of detergent auxiliaries and textile auxiliaries.

Phosphorus source reaction mechanism : Dihydrogen phosphate provides phosphate and phosphorus sources, participating in phosphorus chemical synthesis and conversion—the basis of chemical synthesis raw materials.

All uses of industrial-grade Sodium Phosphate Monobasic Monohydrate

1. Water treatment field

Industrial water treatment agents

It acts as a scale inhibitor and pH adjuster for boiler water and circulating cooling water, inhibiting the deposition of calcium and magnesium scale and preventing scale and corrosion in pipelines.

Corresponding products: boiler water treatment agents, circulating water scale inhibitors, water softeners, etc.

2. Metal processing and surface treatment field

Metal surface treatment and phosphating agents

As a metal phosphating agent, it reacts with the metal surface to form a phosphate conversion film, improving corrosion resistance and coating adhesion.

Corresponding products: phosphating solution, metal rust inhibitor, surface treatment agent, etc.

Electroplating buffer

It acts as a buffer and pH adjuster in electroplating solutions, refining the grain size of the plating layer and improving its density and corrosion resistance.

Corresponding products: electroplating solution buffers, plating solution additives, electroplating chemical raw materials, etc.

3. Daily Chemicals and Cleaning Products

Detergent and cleaning additives

It acts as an adjuvant and buffering component in detergents and cleaning agents, enhancing their detergency, dispersion, and water softening effects.

Corresponding products: laundry detergent additives, cleaning agents, industrial cleaning agents, etc.

4. Paper and textile industries

Paper pH buffer

It acts as a pH buffer and regulator for paper pulp, maintaining the acidity and alkalinity during papermaking and sizing processes.

Corresponding products: papermaking buffers, pulp pH adjusters, papermaking additives, etc.

Textile printing and dyeing and leather tanning auxiliaries

It is used as a pH buffer for dye baths and as a dyeing and printing auxiliary agent, and is also used for pH control in leather processing.

Corresponding products: dye bath buffer, dyeing and printing auxiliaries, leather processing auxiliaries, etc.

5. Building materials and chemical industry

Ceramic glaze additives

It is used as an auxiliary additive for ceramic glazes and bodies, participating in glaze formulation and process adjustment.

Corresponding products: ceramic glazes, raw material additives, building material chemical raw materials, etc.

Chemical Synthesis Raw Materials

It serves as a raw material and intermediate in the synthesis of phosphorus chemicals, providing phosphate groups to participate in the production of various phosphates and phosphorus-based products.

Corresponding products: phosphate intermediates, phosphorus chemical raw materials, chemical synthesis agents, etc.

Industrial buffer

It is used as a general industrial buffer for pH control and buffer system preparation in chemical, biochemical and detection processes.

Corresponding products: industrial buffers, process buffer salts, test buffers, etc.

Summary

Sodium Phosphate Monobasic Monohydrate (CAS 10049-21-5) is the crystalline hydrate of sodium dihydrogen phosphate, composed of sodium ions, dihydrogen phosphate ions, and one molecule of water of crystallization. The dihydrogen phosphate ion possesses weak acidity, buffering properties, coordination ability, and phosphorus source functions, making it a versatile ingredient in industrial applications. It serves as a scale inhibitor in boilers and circulating water systems, a rust-preventing agent for metal phosphating, a buffer in electroplating solutions, an additive in detergents, a pH adjuster in papermaking and dyeing, and a raw material for phosphate chemical synthesis. From industrial water treatment and metal processing to daily chemical cleaning, papermaking, textiles, and building materials chemicals, industrial phosphates quietly support many aspects of modern industry. Understanding its acidic salt structure and phosphate characteristics helps explain why it has become a key, multi-functional raw material in industrial chemicals.