What is trisodium phosphate (CAS 7601-54-9)? What are its uses?

I. What is Trisodium phosphate (CAS 7601-54-9)?

Trisodium phosphate, also known as sodium orthophosphate (TSP), is the sodium salt of orthophosphate obtained by the complete neutralization of phosphoric acid. Its chemical formula is usually written as:

Na3PO4 (CAS No.: 7601-54-9, molecular weight approximately 163.94, dodecahydrate CAS No.: 10101-89-0)

At room temperature, it is a colorless to white needle-like crystal or crystalline powder, odorless, and generally exists in both anhydrous and dodecahydrate forms. The dodecahydrate has a melting point of approximately 73.4℃ and a density of approximately 1.62 g/cm³. It readily effloresces in dry air and loses all its water of crystallization at 100℃. Trisodium phosphate is readily soluble in water, and its aqueous solution is strongly alkaline due to the vigorous hydrolysis of phosphate ions (PO₄³⁻) (pH approximately 11.5 for a 1% aqueous solution, and pH reaching 13-14 for high-concentration solutions). It is insoluble in ethanol.

From a molecular structure perspective, trisodium phosphate consists of three sodium ions (Na+) and one orthophosphate ion (PO4³-), making it a completely neutralized salt of phosphoric acid. Its strong alkalinity endows it with excellent saponification, degreasing, water softening, and buffering capabilities—in the laboratory field, it serves as a buffer, pH adjuster, and biochemical reagent; in the consumer field, its degreasing and water softening abilities are used in household cleaning. This multi-faceted capability of "strong alkali + buffer + water softening" forms the functional basis for its applications beyond the food and industrial sectors.

Chemically, trisodium phosphate is a strongly alkaline substance that reacts with acids to form phosphates, and forms insoluble precipitates with calcium and magnesium ions in water (due to its water softening effect). It may be corrosive to the skin and precautions should be taken if contact is prolonged. Store in an airtight, dry container.

“Trisodium phosphate other than food-grade and industrial-grade” means products sold for research and consumer uses, most commonly including reagent-grade specifications. Compared to food-grade and industrial-grade products, these specifications focus more on the following indicators:

pH and buffering capacity

The buffering performance of the aqueous solution is an important indicator for laboratory applications, and the solution is highly alkaline.

Water-insoluble matter

Water-insoluble matter can affect reagent purity and buffering capacity, and must be kept at a low level.

Moisture

The dodecahedral hydrate differs from the anhydrous hydrate in form, and the moisture content must meet specifications, affecting the accuracy of measurement and storage stability.

What other uses does Trisodium phosphate have?

1. Boiler water softening and water treatment (core application)

Trisodium phosphate is a traditional descaling agent and water softening agent in industrial boiler water treatment. Phosphate ions react with the calcium and magnesium ions in the water to form insoluble phosphate precipitates which are discharged . This prevents scale formation on the boiler heating surfaces and ensures the safe and economic operation of the boiler . This is largely used in boiler water treatment of power, heating and chemicals industries.

2. Scientific research and laboratory applications (reagent grade)

Trisodium phosphate is a common inorganic laboratory reagent. It is used for the preparation of buffer solutions, biochemical experiments and precipitation and separation of metal ions. High Purity versions are used for scientific research experiments requiring high purity and as routine reagents in chemical and biological laboratories.

3. Household cleaning and descaling (consumer grade)

Trisodium phosphate is a powerful degreasing and descaling agent that can be used for cleaning kitchen grease, softening hard water, and removing limescale. It may be found in some household cleaning products.

4. Maintenance of domestic soft water and hot water systems

Trisodium phosphate is used in household water softening equipment and hot water systems for water treatment because it precipitates calcium and magnesium ions, softening the water. This helps to inhibit scale and protect electrical appliances.

4. Textile printing and dyeing industry

Trisodium phosphate is used in scouring, degreasing and water softening of textiles to help remove waxes, greases and impurities from fibres and to improve the effects of bleaching and dyeing. It is an important auxiliary agent in printing and dyeing industry of textiles.

5. Paper Industry

Trisodium phosphate can be used as a softener and additive in pulp boiling and pulping processes to help improve pulp quality and papermaking process stability.

6. Moisture retention and tenderness (core application)

( 1 ) Trisodium phosphate is an important moisture retainer and tenderizer in meat processing. When used in combination with pyrophosphate, tripolyphosphate, etc., it can chelate metal ions, promote muscle protein to absorb water and swell, significantly improve the water retention and tenderness of meat products such as ham, sausage, and meatballs, improve the taste and reduce cooking loss.

( 2 ) In the processing of aquatic products, trisodium phosphate helps products such as shrimp, fish balls, and crab sticks to retain moisture, reduce the loss of juice during thawing and cooking, improve the color and elasticity of the products, and increase the yield.

7. Beverage Emulsification and Stabilization

( 1 ) Trisodium phosphate is used as an emulsifying salt and stabiliser for dairy products. It helps dairy products such as cheese to emulsify evenly when heated, prevent oil separation and improve meltability and texture.

( 2 ) Trisodium phosphate can be used as a stabiliser and pH buffer for beverages, chelating metal ions in beverages, preventing turbidity and precipitation, and assisting in maintaining the clarity and flavour stability of beverages.

8. Quality improvement of flour products

( 1 ) Trisodium phosphate is used in noodle, dumpling wrapper and other flour products. It can adjust pH, improve gluten network structure and help flour products maintain good extensibility and chewy texture.

( 2 ) Trisodium phosphate can be used as an alkaline salt component of compound leavening agents. It can be used in combination with acidic salts in baked goods such as pastries and biscuits to help control the gas production rate and improve the leavening effect.

9. Teaching and Popular Science Experiments

Trisodium phosphate is used in chemical teaching demonstrations and experiments to assist learners in comprehending the hydrolysis of strong base-weak acid salts, buffering effects and the principle of soft water. It is a common teaching reagent in middle school and university chemistry laboratories.

11. Other Applications

With the development of research, the application scope of trisodium phosphate continues to expand, including standard reagent supply, analytical testing services, and customized fine chemicals.

Summarize

Trisodium phosphate (TSP) is a white crystalline powder, a strong base-weak acid salt, readily soluble in water, and its aqueous solution is strongly alkaline. It possesses multiple functions, including water softening, buffering, and degreasing. In daily life, we indirectly encounter it through detergents, boiler water treatment, metal products, textile printing and dyeing, and the food industry. Beyond food and industry, reagent-grade trisodium phosphate is widely used in scientific research and laboratories, household cleaning and descaling, household water softening, and educational experiments, making it an important phosphate chemical connecting "daily use" with "health, scientific research, and consumption."