Sodium Hexametaphosphate

An Introduction to Sodium Hexametaphosphate

Sodium hexametaphosphate is a chemical compound comprising of a blend of polymeric metaphosphates. It is a hexamer comprising of a chain of NaPO3 units. 

A hexamer is nothing but a polymer made up from six molecular compositions of a monomer. The other name of this chemical composition is also known as Calgon. The sodium hexametaphosphate formula is (NaPO3)6.

Chemistry is a complex subject comprising of concepts, formulae and chemical composition. Therefore, read these concepts related to this compound in detail to score good grades in exams and enhance your knowledge.

What is Sodium Hexametaphosphate?

Sodium Hexametaphosphate is a water-soluble compound consisting of reoccurring polyphosphate chains. It is a complex resulting through a thermal procedure of monosodium orthophosphate. 

It occurs as colourless translucent glass-like material or has a powdery appearance. It is also known as a kind of sodium metaphosphate polymers. It has the capability of forming complex soluble compositions for specific metal ions, such as calcium and magnesium, etc.

It is what sodium hexametaphosphate is known as primarily. The compound comprises of chemicals like sodium and metaphosphates. 

Physical and Chemical Properties 

Read from the following about the chemical and physical properties of sodium hexametaphosphate. The below details will help you gather an in-depth knowledge regarding the compound.

Physical Attributes

  • The compound appears as white powder or crystals, and it is completely transparent.

  • It lacks colour and odour.

  • The chemical compound dissolves in water quickly. However, it does not dissolve in organic solutions.

  • The pH level of the compound is 8.6, which is above the neutral pH level of 7.

  • The refractive index for the complex is 1.482.

Chemical Attributes

  • The boiling point of this compound is 1500 degree Celsius or 2730 degree Fahrenheit.

  • The melting point of Calgon is 628 degree Celsius or 1,162 degrees Fahrenheit.

  • The molecular weight of this chemical complex is 611.7704 g mol-1.

  • The hydrogen bond acceptor and donor numbers account to 18 and 0, respectively.

  • The exact mass of this complex accounts to 611.689651 g/mol, which is identical to its monoisotopic mass.

  • The topological polar surface area of sodium hexametaphosphate is 296 Ų.

  • The property value of its complexity amounts to 513, and the unit count of its covalent-bond are 7, respectively.

  • The heavy atomic value of this chemical compound Calgon is 30.

  • The compound hydrolyses to sodium trimetaphosphate or sodium orthophosphate in water-based solutions, especially under acidic circumstances.

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Preparation Procedure 

The compound (NaPO3)6, which is also popularly named as Calgon, has a specific preparation procedure. The below steps explain it further.

  • The complex can be obtained when monosodium orthophosphate goes through a thermal process or heating. Initially, it generates sodium acid pyrophosphate. The reaction is shown below as:

2 NaH2PO4 → Na2H2P2O7 + H2O

  • Further, this pyrophosphate gets heated to generate the final complex (NaPO3)6 following by rapid cooling. The chemical reaction gets depicted below as:

3 Na2H2P2O7 → (NaPO3)6 + 3 H2O

Pop Quiz 1

  1. Which of the following chemical complex gets applied in water treatment?

  1. Sodium phosphate

  2. Nitrous oxide

  3. Magnesium phosphate

  4. Calgon

  5. None of these


Sodium hexametaphosphate has various uses in industrial, consumer and agricultural purposes due to its intrinsic properties. Some of these include:

Industrial uses:

  • To prepare solution in industries for the production of ceramics, including additives is a mandatory step to obtain a proper fluid paste. Therefore, the compound (NaPO3)6 gets used as dispersing agents in the manufacture of ceramics and enamels.

  • Besides, it helps in breaking down of clay and analysing of various types of soil textures. It is another reason why the compound finds applications in the ceramic industry.

  • In paper pulp industries, many products require the applications of phosphates. Phosphates comprise dispersing properties that help in reducing the caking of resins and pigments when they are in suspension. Additionally, they play a crucial role in the coating of materials.

The main phosphate that finds its applications in the paper industry is (NaPO3)6. However, phosphates get used in other forms too.

  • Due to its dispersing attributes, the chemical finds its uses in paints also. This attribute is beneficial for the paint industry.

  • The chemical complex finds its applications as a food additive in various industries that helps in enhancing the quality and durability of foods. Its chemical properties enable to preserve food particles for a long period.

  • The compound on combining with sodium carbonate causes the pH level to increase from 8.0 to 8.6. Such an increase in the pH level is beneficial in water softening, and the manufacture of detergents.

  • Additionally, the chemical compound acts as an active element in tubes of toothpaste, and it also helps in the prohibition of tartar formation.

  • Moreover, the complex gets used as a solvent for cleaning and degreasing purposes.

  • It also finds its applications in drilling mud since it acts as a viscosity regulator.

  • As an emulsifier, the chemical complex finds application in the manufacture of coated paper.

  • The chemical complex also has wide uses in reducing the hardness of the water. Due to this property, it is applicable in boiler and industrial water.

Agricultural and Consumer Uses:

  • It also gets used in agricultural chemicals that help in the growth of plants and increases its productivity. It primarily gets applied in non-pesticidal purposes that do not interfere in pests’ interaction.

  • It also gets used as a water-retaining agent. Due to this property, the complex finds its applications in meat and sausage processing. It enables the non-vegetarian foods to lasts for a long period and reduces its anti-microbial activities.

  • The compound also acts as a stabiliser for canned fruits, and milk, and it helps in maintaining its natural colour. Apart from these, it gets used in artificial maple syrup, packaged egg whites, fish fillets and salad dressing, etc. 

  •  It also gets used in beverages to store them for a longer span. 

Effects of Calgon 

Calgon or Graham’s Salt is a white powdery substance comprising of sodium and metaphosphates. Although the chemical compound has wide-scale application in various sectors, yet these have some effects on human beings, and plants due to prolonged exposure.

The following pointers show some of its impacts. Read them to know more.

  • The chemical compound can result in long-term negative impact in the aquatic surroundings.

  • If it is accidentally inhaled or swallowed, the complex can cause damage to the well-being of a person. When the compound gets absorbed in a human frame, it results in vomiting, diarrhoea and nausea.

  • The compound can also cause headache and dizziness when it gets absorbed by a person for short durations.

  • It also causes fever, tiredness and low blood pressure when it gets injected in a body for a short span.

  • The complex can also cause gastrointestinal infection and allergic reactions when someone comes in its exposure for fewer periods.

  • Prolonged exposure to the compound can result in slower pulse rate, cyanosis and even coma along with acute spams in the body and wrist.

  • If anyone comes in close contact with the compound for a larger span, it causes pancreatic cancer. It is capable of increasing cancer-causing cells in the body.

  • If someone comes in close contact with this compound, it can result in severe eye irritation. However, the severity of the circumstance varies with the prevalent concentration of this substance.

  • Kidney problems are also an evident side-effect of the compound on a body.

  • Direct contact of this chemical compound through open wounds, abrasions or lesions can result in damage to sensitive-skinned people.

  • Loss of essential minerals from the bones can occur due to long-term exposure to the chemical.

Pop Quiz 2

  1. Calgon is an industrial name given to the compound (NaPO3)6. Is the statement true or false?

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FAQ (Frequently Asked Questions)

1. What is the formula of Calgon?

Ans. Calgon is a popular name propounded for the chemical compound sodium hexametaphosphate. The Calgon formula for this compound is Na6P6O18.

2. What are the other common names of Sodium Hexametaphosphate?

Ans. The commonly used names of this chemical compound are glassy sodium, Graham’s salt. It is also known as metaphosphoric acid, hexasodium metaphosphate and hexasodium salt. Besides, it is popularly known as sodium hexametaphosphate Calgon.

3. How harmful is Graham’s salt or Na6P6O18?

Ans. The chemical compound Na6P6O18 has both short term and long term uses in a body. When tested in laboratory on animals, it shows kidney swellings, calcium loss from bones, skin irritations and muscular changes in fibre, etc.

4. What is the role of chemical compound Na6P6O18 in food?

Ans. The complex gets used in foods as it acts as a preservative and a stabiliser. It plays a key role in improving the food texture as it helps in water binding and retention, thickening and emulsification. Moreover, it helps to protect the nutrition value of food particles and canned products.