Difference between phosphorus, phosphoric acid and phosphates

Frequently Asked Questions

General Questions

What are phosphates, and what is the difference between phosphorus, phosphates and phosphoric acid

Phosphorus is an element that occurs in nature and is widely distributed in combination with other minerals. In your high school chemistry class, it was presented to you as one of the elements on the Periodic Table. Phosphates are natural compounds – salts containing phosphorus and other minerals. The main minerals in bones and teeth are types of phosphates with the scientific names of hydroxyapatite or tricalcium phosphate. Phosphoric acid is produced from phosphates by reacting with sulphuric acid.

Are phosphates natural?

Phosphate rock is mined from the earth. The rock is crushed and purified to form phosphoric acid, which may be reacted with caustic soda of lime to produce purified phosphate salts.

How are phosphates formed?

Centuries ago, phosphorus was obtained from animal bones and urine. Over time, there was an insufficient supply of bone to meet the demand for purified phosphorus. Today, phosphate rock is mined to obtain phosphorus. The natural phosphate rock includes clay and other minerals, so it must be purified to isolate phosphorus in the form of phosphoric acid. The acid is reacted with alkaline salts to produce purified phosphates.

Are phosphates essential to life?

Yes. Phosphates are nutrients and are essential to human, animal and plant life. They have critical functions in key biochemical processes such as metabolism. Our bodies are made of many phosphorus-containing compounds that play a major role in:

  • Genetic material - the DNA and RNA that makes each of us unique
  • Cellular membranes
  • Teeth and bones
  • Human energy systems
  • Cell signaling systems, which regulates diverse functions from the acid-base balance in the body to hormonal responses.

Plants also need phosphorus, and phosphorus-containing compounds are vital to photosynthesis.

Food Questions

Do I need phosphorous in my diet to be healthy?

You do. Phosphorus is an essential mineral in all living things, and is critical to each cell's ability to store and convert energy. Like most nutrients, some phosphorus is continually lost during normal biological processes and must be replenished. In combination with calcium, an ongoing phosphorus supply (in the form of phosphates) is essential to maintaining healthy bones and teeth and proper blood chemistry. The Daily Reference Intakes for phosphorus are included in the Institute of Medicine’s (IOM) report, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride.

For more information about phosphorus in the diet click here.

Why are phosphates in my baking mix?

Phosphate salts act as leavening agents that "fluff up" foods we like to eat, such as cakes, biscuits, breads and pancakes. Unlike yeast recipes, such as sourdough, phosphates have no taste and can be used for a wide variety of baking products, such as prepared doughs, pizzas and cake mixes. Phosphates react with sodium bicarbonate to release carbon dioxide, providing the leavening for a wide array of products we see on our store shelves today.

Why are phosphates in toothpaste?

Many toothpaste formulations include calcium and sodium phosphates for their mild abrasiveness and effective whitening properties. Other phosphates also are used as fluoride carriers to improve tooth health. These ingredients help remove food particles that otherwise could contribute to tooth decay.

Why should I have phosphorus with calcium supplements?

Mammalian bones and tooth enamel are mostly made of calcium phosphate. For this reason, most multi-vitamin supplements contain phosphorus in addition to calcium to supply the necessary minerals for bone building in our bodies. Calcium phosphates also have excellent "excipient," or tablet-forming, properties. In prescription pharmaceuticals and over-the-counter remedies, calcium phosphates help bind the ingredients into tablet form.

Why do sandwich ingredients contain phosphates?

Phosphates provide benefits to certain sandwich ingredients:

  • Lunchmeat, ham, or other processed meat retain moisture and tenderness better during storage thanks to sodium phosphate.
  • Cheese keeps its shape and melting properties because of sodium phosphates and enhanced nutritional value as a calcium phosphate fortified product.
  • Canned tuna meat can develop a glassy or sandy appearance caused by the mineral struvite. Adding a small amount of sodium phosphate retards the formation of this mineral in tuna.
  • Calcium phosphate in bread retards a strain of bacteria that would otherwise make bread appear as if it contained rope.
Why are phosphates in pet foods?

Calcium and phosphorus are essential minerals for dogs. These minerals are mainly supplied from the diet. Phosphates can contain calcium and phosphorus to help maintain healthy teeth and bones.

  • Phosphates bind ingredients in canned pet foods.
  • Phosphates found in treats can help clean teeth and control tartar.
  • Phosphoric acid provides a “tart” flavor desired by cats.

For more information about the phosphorus content of various foods click here.

Consumer Product Questions

Why are phosphates in fertilizer?

Phosphates are natural nutrients necessary for plant growth and health, and are the most stable compounds to deliver phosphorus to plant roots. When choosing the right fertilizer, the phosphorus content is one of the key properties to consider, along with levels of nitrogen (for growth and greening) and potassium (for drought and disease resistance). Highly soluble ammonium phosphate and potassium phosphate salts can be blended with other sources of nitrogen and potassium to develop a variety of products to meet specific fertilizer needs.

Why are phosphates used in cleaning products and detergents?

Phosphates act as a key ingredient in many cleaning products and detergents. They serve multiple functions, providing properties that increased the effectiveness of a variety of products. Phosphates help remove any hardness ions present in the water (such as calcium, magnesium, or iron), which allows other components in the cleaning process to work more effectively. And, phosphates help remove dirt particles from the surface being cleaned, through the suspension of fine particles for efficient removal in the rinse. Because of phosphate's buffering capabilities, soil and other cleaning components are prevented from shifting the pH of a cleaning solution, which can diminish its optimum cleaning efficiency range. Phosphates offer a trio of benefits: the application of phosphates prepares the water or cleaning environment then traps and holds the dirt or oils so that it can be rinsed away.

Why are phosphates in fire extinguishers?

Various phosphates are used in fire extinguishing as chemical powders. Fire-extinguisher powders based on the ammonium phosphates are effective against all classes of fires, and, therefore, are the basis for most multipurpose fire extinguishers. With the action of heat, ammonium phosphates release non-combustible gases and carbonizing substances, which extinguish the flames. Tricalcium phosphate often serves as a free-flowing agent for the fire-extinguishing powder. Other dry chemicals used for fire extinguishing, such as sodium and potassium bicarbonate powders, are only effective with Class B (flammable liquids) and Class C (electrical fires). However, these other products are ineffective against fires with Class A compounds, such as paper, wood, and cotton fabrics, since problems of smoldering, flare-up or re-ignition often occur.

Environmental Questions

How do phosphates enter the environment?

Many phosphates occur naturally in the environment as minerals and as essential nutrients for plant and animal life. In the phosphorus nutrient cycle, plants absorb phosphates from water and soil. Phosphates are available to animals and humans when plants (and other animals) are consumed and are then returned to the environment through animal and human waste and decomposition of plants and animals.

Where do phosphates go in the environment?

Crops take up phosphates from fertilizer, all of which may not be utilized. Some phosphates remain in the soil in a mineralized form and some are lost by soil erosion and runoff. Agricultural runoff and unprocessed animal waste may reach streams and lakes. Although phosphates are a nutrient, and in combination with other nutrients, support aquatic life, they can have an adverse effect on ecosystems at higher concentrations. For example, a condition known as "eutrophication" can occur by which a lake or pond becomes rich in plant nutrient minerals and organisms, but often deficient in oxygen in midsummer. This can have a temporary adverse impact, with the situation reversing as the phosphates eventually are precipitated (re-mineralized).


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