Sodium Hexametaphosphate

1. Product Overview

Sodium hexametaphosphate (SHMP) is an inorganic polyphosphate compound belonging to the metaphosphate family. It is a hexamer of composition (NaPO₃)₆, though commercial SHMP is typically a mixture of polymeric metaphosphates, with the hexamer being one component . Such a mixture is more correctly termed sodium polymetaphosphate.

Its chemical formula is often represented as (NaPO₃)₆ or Na₆O₁₈P₆ with molecular weight of approximately 611.77 g/mol . CAS numbers vary by grade and specification, with common identifiers including 10124-56-8  and 68915-31-1 .

SHMP appears as a white crystalline powder, colorless transparent glassy solid, or granular material, depending on processing . It is odorless and highly soluble in water, with the characteristic ability to sequester metal ions—particularly calcium and magnesium—making it invaluable across food processing, water treatment, industrial manufacturing, and household products.

The product is globally recognized as a food additive with E number E452i  and is produced in various grades including food grade, technical grade, and industrial grade to meet diverse application requirements .

2. Key Features

• Powerful Sequestration Ability: Forms stable, water-soluble complexes with calcium, magnesium, iron, and other metal ions, effectively softening hard water and preventing scale formation . Each 100g can chelate approximately 19.5g of calcium .

• Exceptional Dispersion Properties: Acts as an effective deflocculant and dispersing agent, breaking down clay aggregates and keeping fine particles suspended in liquid systems. Widely used in ceramic production and soil texture analysis .

• Multi-Function Food Additive (E452i) : Serves multiple roles in food processing:

• Enhances water retention in meat products (improving yield and texture) 

• Stabilizes emulsions and prevents fat oxidation 

• Prevents discoloration in fruits and vegetables 

• Clarifies beverages and prevents haze formation in beer 

• Improves texture in dairy products and ice cream 

• Excellent Water Solubility: Readily dissolves in water (soluble in all proportions), while remaining insoluble in organic solvents, facilitating easy incorporation into aqueous systems .

• pH Buffering Capacity: 1% aqueous solutions typically exhibit pH in the range of 5.8-7.7 , providing mild acidity to near-neutral conditions suitable for most applications.

• Thermal Stability: With a melting point of 550-628°C and boiling point of 1500°C , SHMP maintains stability across a wide temperature range, though it hydrolyzes in aqueous solution under acidic conditions .

• Anti-Corrosion Properties: At low concentrations, inhibits steel corrosion and prevents formation of scale-forming compounds (calcium carbonate and calcium sulfate) in water systems .

• Multiple Grade Availability: Offered in food grade (meeting strict purity standards for heavy metals), technical grade, and industrial grade, allowing precise selection for specific applications .

3. Technical Specifications with Explanations

4. Applications

Food & Beverage Industry (as E452i)

SHMP is one of the most versatile food additives, serving multiple functions across diverse food categories:

Meat & Seafood Processing:

• Enhances water retention in meat products, improving yield and juiciness 

• Prevents fat oxidation and rancidity 

• Used in roast beef, fish fillets, ham, and sausages 

• Sprayed on Cured meat to improve Anticorrosion performance 

Dairy & Frozen Products:

• Improves texture in ice cream (increases expansion capacity, enhances emulsification) 

• Prevents gel precipitation in milk products and canned milk 

• Used in cheese powders, dips, and imitation cheese 

• Stabilizes whipped toppings and packaged egg whites 

Beverages:

• Clarifies beer and prevents haze formation 

• Stabilizes bottled beverages and soft drinks 

• Inhibits vitamin C decomposition in fruit drinks 

• Used in artificial maple syrup 

Fruits & Vegetables:

• Stabilizes natural pigments in canned fruits and vegetables 

• Prevents discoloration in processed produce 

• Used in fruit jelly and preserves 

Other Food Applications:

• Prevents gel formation in condensed milk 

• Used in salad dressings, breakfast cereals, and herring products 

• Increases viscosity in soy sauce and miso 

• Shortens fermentation time in bean paste 

Water Treatment

• Scale Inhibition: Prevents calcium carbonate and calcium sulfate scale formation in boilers, cooling towers, and industrial water systems 

• Corrosion Control: At low concentrations (0.5 mg/L), inhibits steel corrosion 

• Water Softening: Effectively sequesters calcium and magnesium ions, with 100g capable of chelating 19.5g of calcium 

• EDI/RO Systems: Used as an antiscalant in electrodeionization and reverse osmosis systems 

Industrial Applications

Ceramics & Construction:

• Deflocculant: Disperses clay particles in ceramic slip casting, improving fluidity and reducing water requirements 

• Cement Additive: Acts as a hardening accelerator in cement production 

Detergents & Cleaners:

• Water Softener: Binds calcium and magnesium in hard water, enhancing detergent performance 

• Dispersant: Prevents redeposition of soil in laundry applications 

• Industrial Cleaners: Used in bottle washing compounds and metal cleaners

Textile Industry:

• Water Softener: Prevents hard water interference with dyeing processes 

• Boiling-off Agent: Enhances fabric preparation and scouring 

Paper Industry:

• Dispersant: Improves pulp uniformity and paper quality 

• Filler Retention: Enhances retention of fillers and fine fibers

Metal Processing:

• Corrosion Inhibitor: Protects metal surfaces 

• Surface Treatment: Used in metal finishing and cleaning 

Petroleum Industry:

• Drilling Fluid Thinner: Improves flow properties of drilling muds 

Mining & Mineral Processing:

• Flotation Agent: Used in ore flotation processes 

• Slurry Dispersant: Enhances handling of mineral slurries

Oral Care & Pharmaceuticals

• Toothpaste Additive: Active ingredient in anti-staining and tartar prevention formulations 

• Dental Materials: Used as a retarder in dental alginate impression materials 

• Pharmaceutical Excipient: Provides stabilizing properties in drug formulations 

Photographic & Other Applications

• Photographic Developing: Used in photographic processing solutions 

• Biomedical Research: Studied for antimicrobial formulations and nanoparticle stabilization 

5. Product Grade Comparison

6. Purchasing & Selection Guide

Select by Application Area

1. Food & Beverage Manufacturers:

• Meat processing: Focus on water retention properties 

• Dairy applications: Emphasize emulsification and stabilization 

• Beverages: Prioritize clarity and stability 

• P₂O₅ content (67.0-70.0%) 

• Heavy metals (Pb ≤4 μg/g, As ≤0.75 μg/g) 

• Chlorides (≤100 μg/g) and sulfates (≤100 μg/g) 

• Must select Food Grade (E452i) meeting strict purity standards 

• Verify compliance with local regulations (FDA 21 CFR, EU Regulation 1333/2008)

• Request Certificate of Analysis confirming:

• Consider KOSHER/Halal certification if required for target markets

• Select based on specific food application:

• Boiler water treatment: Scale inhibition and corrosion control 

• Cooling towers: Calcium carbonate inhibition 

• EDI/RO systems: Antiscalant properties 

• Choose Technical Grade or Industrial Grade depending on scale

• Focus on P₂O₅ content (≥65%) and chelation capacity 

• Consider specific formulation requirements:

• Higher purity may be required for potable water applications

• Ceramic industry: Select Technical Grade with consistent dispersion properties 

• Detergent formulators: Focus on water softening and sequestration capacity 

• Textile processors: Prioritize iron content control (≤200 ppm) 

• Paper industry: Emphasize dispersion efficiency 

• Select high-purity grades meeting pharmacopoeia standards

• For toothpaste: Ensure compatibility with fluoride and other ingredients 

• For dental materials: Verify setting time retardation properties 

• Analytical grade for precise experimental work

• FCC grade for food-related research 

• Technical grade for general laboratory applications 

Important Selection Considerations

• P₂O₅ Content vs. Application:

• Higher P₂O₅ content (67-70%) generally indicates better quality and performance 

• Food applications typically require the highest P₂O₅ content 

• Industrial applications may accept lower P₂O₅ content for cost savings

• Physical Form:

• Powder: Fast dissolution, suitable for most applications 

• Granules: Reduced dust, better flow properties, slower dissolution 

• Glassy solid: Requires crushing before use; typical for industrial applications 

• Hygroscopicity Management:

• SHMP is highly hygroscopic; requires sealed packaging 

• Consider packaging size based on consumption rate to minimize exposure

• Plan for rapid use after opening

• Regulatory Compliance:

• Food applications: Must comply with local regulations (FDA, EU, China GB)

• Export requirements: Verify target market specifications (JECFA, FCC, etc.) 

• Kosher/Halal certification may be required for certain markets

• Hydrolysis Considerations:

• SHMP hydrolyzes in aqueous solution, particularly under acidic conditions 

• Solutions should be used promptly, especially at elevated temperatures

• For long-term stability, consider dry storage and fresh solution preparation

7. Frequently Asked Questions (FAQ)

Q: What is the difference between sodium hexametaphosphate and sodium polyphosphate?

A: Sodium hexametaphosphate (SHMP) specifically refers to the hexameric form (NaPO₃)₆, but commercial SHMP is actually a mixture of polymeric metaphosphates of varying chain lengths . Sodium polyphosphate is a broader term encompassing various chain-length phosphates. The commercial product called "sodium hexametaphosphate" is more accurately described as sodium polymetaphosphate, with the hexamer being one component of the mixture .

Q: Why are there multiple CAS numbers for sodium hexametaphosphate?

A: Different CAS numbers reflect different grades, specifications, or production methods:

• 10124-56-8: Most common identifier for general and technical grades 

• 68915-31-1: Often used for FCC grade and some industrial specifications 

• 50813-16-6: Alternate identifier for some applications 

When ordering, specify both CAS number and grade to ensure correct product.

Q: Is sodium hexametaphosphate safe for use in food?

A: Yes, when used according to regulations. SHMP is approved as a food additive (E452i) in many countries including the US (FDA 21 CFR), EU, China, and others . Food-grade SHMP must meet strict purity specifications including limits on heavy metals (Pb ≤4 μg/g, As ≤0.75 μg/g) . It has been extensively studied and is generally recognized as safe (GRAS) when used in compliance with good manufacturing practices.

Q: How does SHMP soften water?

A: SHMP softens water through sequestration (chelation) . The polyphosphate chains bind strongly to calcium (Ca²⁺) and magnesium (Mg²⁺) ions, forming stable, water-soluble complexes . This prevents the metal ions from precipitating as insoluble soaps or scales, effectively "softening" the water without removing the ions. Each 100g of SHMP can chelate approximately 19.5g of calcium .

Q: Why does SHMP sometimes appear as a glassy solid and sometimes as a powder?

A: The physical form depends on the production process and quenching method . During manufacturing, molten SHMP is rapidly cooled (quenched) to prevent depolymerization. Rapid quenching produces a glassy, transparent solid that can be crushed into powder or sold as flakes . Subsequent grinding produces white powder. Both forms have identical chemical properties; the choice depends on handling and dissolution requirements.

Q: How should SHMP be stored?

A: SHMP is highly hygroscopic and absorbs moisture from air, leading to caking and hydrolysis . Store in tightly sealed containers in a cool, dry, well-ventilated area with temperature below 30°C . Protect from direct sunlight and humidity. Keep away from strong acids (incompatible). Under proper conditions, shelf life is typically 2-5 years depending on grade and packaging .

Q: Can SHMP be used in toothpaste?

A: Yes, SHMP is used as an active ingredient in toothpaste formulations for anti-staining and tartar prevention . It works by binding calcium ions in saliva, preventing their incorporation into dental plaque and calculus. It also helps prevent stain formation by binding with chromogens before they can adhere to tooth surfaces .

Q: What happens if SHMP is added to acidic solutions?

A: In acidic conditions (low pH), SHMP undergoes hydrolysis, breaking down into shorter-chain phosphates and eventually orthophosphates . This hydrolysis reduces its chelating effectiveness. For applications requiring stability, maintain pH above 5-6, or use freshly prepared solutions. Hydrolysis is accelerated by heat and low pH.

Q: How do I dissolve SHMP for my application?

A: SHMP dissolves readily in water. For optimal dissolution:

• Add slowly to room temperature or warm water with stirring

• For concentrated solutions, use warm water (40-50°C) to accelerate dissolution

• Avoid extremely hot water (>80°C) which may promote hydrolysis

• Do not add acid to the dissolution water

• Prepare fresh solutions when possible, as aged solutions may have reduced effectiveness due to hydrolysis

Q: Is SHMP biodegradable?

A: As an inorganic compound, SHMP does not biodegrade in the same way organic compounds do. However, it hydrolyzes in water to orthophosphates, which are natural components of the environment. Concerns about phosphate contribution to eutrophication have led to reduced use in laundry detergents in some regions.

Q: What are the main impurities in SHMP?

A: Depending on grade, main impurities include:

• Chlorides (Cl) : ≤50-100 ppm 

• Sulfates (SO₄) : ≤100-300 ppm 

• Iron (Fe) : ≤50-200 ppm 

• Heavy metals (Pb) : ≤4-30 ppm 

• Arsenic (As) : ≤0.75-10 ppm 
  Food grade has the strictest limits on toxic elements .

Q: Can SHMP be used in ceramic production?

A: Yes, SHMP is widely used as a deflocculant in ceramic slip casting . It disperses clay particles by adsorbing onto particle surfaces and creating electrostatic repulsion, reducing water requirements and improving fluidity of ceramic suspensions . This enables production of high-density, low-porosity ceramic bodies.

Q: What is the difference between SHMP and STPP (sodium tripolyphosphate)?

A: Both are phosphate-based sequestrants, but they differ in structure and properties:

• SHMP: Polymeric metaphosphate (long chains), better for calcium sequestration at higher temperatures

• STPP: Linear tripolyphosphate (pentasodium salt), faster dissolving, better for cold water applications
  The choice depends on specific application requirements.

8. Delivery, Certification & Service

Delivery Capabilities

• Inventory Status: Common grades available from regional warehouses (US, Europe, Asia)

• Sample Program: Small quantities available for research institutions and manufacturers for formulation testing and evaluation

• Packaging Options:

• Research quantities: 500g, 1kg, 5kg bottles or bags 

• Industrial quantities: 25kg paper bags or drums (standard) 

• Bulk quantities: 50kg bags, 500kg supersacks, 20 MT containers for large-volume customers

• Custom packaging: Available for volume customers (IBC totes, flexitanks, custom labeling)

• Shipping: Non-hazardous material under DOT/IATA regulations; standard freight shipping available (express, LTL, full truckload, container) 

Quality Certifications

• Certificate of Analysis (COA) provided with each batch for qualified grades, documenting:

• Appearance

• P₂O₅ content

• pH (1% solution)

• Heavy metals (Pb, As)

• Chlorides, sulfates

• Loss on drying

• Clarity of solution (food grade)

• Safety Data Sheet (SDS) available in multiple languages

• Product Specification (PS) documenting chemical composition, physical properties, and storage requirements

• Certificates of Origin (COO) available upon request for customs and regulatory compliance

• Additional certifications available:

• KOSHER certification

• Halal certification

• Food-grade (E452i) compliance documentation

• FCC certification for food applications 

• ISO 9001 quality management certification

Regulatory Compliance

• Food Grade: Meets E452i specifications 

• FCC Grade: Meets Food Chemical Codex requirements 

• Export Documentation: Full compliance documentation for international shipping

• REACH Status: Registered under EU REACH; compliance documentation available

• TSCA: Registered for US commerce 

Technical Support & Services

• Technical Consultation: Application specialist team available for formulation assistance, chelation guidance, and regulatory support

• Custom Services: Tailored purity specifications, particle sizing, and packaging options for long-term partnership customers

• Regulatory Support: Documentation packages for product registration in target markets, including food additive dossiers

Documentation Available

• Certificate of Analysis (COA)

• Safety Data Sheet (SDS/MSDS)

• Technical Data Sheet (TDS)

• Product Specification (PS)

• Certificate of Origin (COO)

• KOSHER Certificate (where applicable)

• Halal Certificate (where applicable)

• Food Grade Compliance Statement (E452i)

• FCC Compliance Statement 

• Allergen Declaration

• GMO-Free Statement

• BSE/TSE Statement