Sodium Hexametaphosphate (SHMP)

Sodium Hexametaphosphate (SHMP) ,CAS:1024-56-8,is an inorganic salt and a member of the polyphosphate family. While its chemical formula is often represented as (NaPO₃)₆, suggesting a simple cyclic molecule, commercial-grade SHMP is typically a complex mixture of polymeric metaphosphates of varying chain lengths, with the hexamer form being a major constituent.

Basic Information:

Sodium Hexametaphosphate (SHMP)

CAS:1024-56-8

Total phosphate（P205）%，68%

Inactive phosphate（P2O5）%，7.5

Water Insoluble %，≤0.02

Fe%，≤ 0.01

pH（10g/L)，5.8~6.5

Appearance，White powder, with no visible black spots

Key Functional Properties:

The widespread utility of SHMP stems from three fundamental chemical properties:

1. Chelation: This is its most crucial function. The structure of SHMP allows it to tightly bind to metal ions in water, particularly calcium (Ca²⁺), magnesium (Mg²⁺), and iron (Fe²⁺/³⁺). It forms stable, soluble complexes with these ions, effectively "sequestering" them. This prevents the ions from forming insoluble precipitates (scale), making SHMP an excellent water softener.

2. Dispersion (Deflocculation): SHMP acts as a powerful dispersing agent. It adsorbs onto the surface of suspended particles (like dirt, clay, or pigments) and charges them negatively. The resulting electrostatic repulsion between particles prevents them from coagulating and settling. This keeps particles suspended and dispersed in the solution.

3. Peptization: It can break down aggregates of particles into smaller, dispersed units.

Buffering: It provides a buffering effect, helping to maintain a stable pH in solutions, which is important in many industrial and food processes.

Applications:

These properties make SHMP a versatile chemical with applications across numerous industries.

1. Industrial and Water Treatment (Primary Use)

Water Softening: Its primary use is as a scale inhibitor in industrial water systems, including boiler feed water, cooling towers, and reverse osmosis membranes. By chelating scale-forming ions, it prevents damaging scale buildup on equipment.

Detergent Builder: Historically, it was a key component in powdered detergents and dishwashing compounds to soften water, enhance cleaning efficiency, and suspend dirt (anti-redeposition agent). Its use has declined in many regions due to environmental regulations on phosphates.

Mining and Mineral Processing: Used as a dispersant and deflocculant in drilling muds. It also acts as a depressant in mineral flotation processes (e.g., to separate phosphate rock from silica).

Textile Industry: Serves as a dispersing agent in dyeing processes to ensure even color distribution and as a water softener.

Ceramics Industry: Acts as a deflocculant in ceramic slips (slurries) to reduce viscosity and improve casting properties.

2. Food Industry (Food Additive E452i)

In food, it is used as a multi-functional additive (INS number 452i).

Emulsifier and Stabilizer: Prevents the separation of fats and water in products like processed cheese, whipped toppings, and milk-based drinks.

Sequestrant: Chelates metal ions that can catalyze lipid oxidation (rancidity), cause discoloration, or promote flavor deterioration.

Texture Modifier and Moisture Retention Agent: Used in meat and seafood products (e.g., sausages, fish fillets) to improve tenderness, juiciness, and yield by binding water.

PH Regulator: Helps stabilize the pH of food products.

Other Applications:

Oral Care: Found in some toothpastes as a gentle abrasive to help remove stains and as a tartar control agent by chelating calcium in saliva.

Paint and Pigment Dispersion: Helps in the grinding and stabilization of pigments.

Safety and Environmental:

Safety: SHMP is generally recognized as safe (GRAS) for use in food at prescribed levels. However, ingestion of large amounts can cause gastrointestinal irritation. Its dust can be mildly irritating to the eyes and respiratory system.