What is Phosphoric Acid

by John Staughton (BASc, BFA) last updated -

Phosphoric acid is one of the most commonly used and widely studied mineral acids, and due to its presence in so many consumer products, it is important to know its effects and potential risks.

What is Phosphoric Acid?

When you look at a can of carbonated soda, one of the main ingredients is phosphoric acid, a colorless, odorless, acid with the chemical formula of H3PO4. It is produced through two main processes; the raw form is made by treating phosphorous-containing rock with sulphuric acid, while the commercial-grade variety is usually made by chemically treating white phosphorous, as per a detailed paper published in the U.S. National Library of Medicine. Its unique and versatile properties make it ideal for inclusion in many different products, particularly because of its pleasant taste when appropriately diluted. [1]

Not only is this acid used in many industrial and commercial processes, but it is also found in natural sources, such as various fruits and their juices. The amount of phosphorous that we take in on a daily basis must be monitored, as, unlike many other micronutrients in our diet, too much phosphorous can result in a number of health issues.

Chemical formula for phosphoric acid

Phosphoric acid is an acid with the chemical formula H ₃PO ₄. Photo Credit: Shutterstock


As mentioned, phosphoric acid is a relatively weak acid with corrosive properties that can wear down alloys, porcelain, and ferrous metals. Composed of 4 atoms of oxygen, 3 atoms of hydrogen, and 1 atom of phosphorous, this acid is soluble in alcohol, but only partially dissociates in water. Depending on its concentration and temperature, phosphoric acid will either be a transparent solid or a sparkling liquid. It is a non-volatile liquid and has a somewhat syrupy consistency in its liquid form. This simultaneously flexible and stable structure is partly why it has become so widely used around the world.

As a bactericide and disinfectant substance, it is able to prevent the growth of bacteria or fungi, particularly in food and beverage applications, according to a study published in the Journal of Applied Oral Science. As the name suggests, it is also acid, and thus works as an acidulant in various applications. [2]

Uses of Phosphoric Acid

This chemical is used in an eclectic range of industries, from agriculture and food and beverage to dentistry and industrial cleaning.

Food and Beverage

The most relevant use of phosphoric acid for most people is in the food they eat. Phosphoric acid is a major ingredient in most carbonated soft drinks, particularly those that are of a darker color. They provide some of the bubbling acidity, as well as a sweetly pleasant flavor. It is also included in many foods as an acidity regulator, such as in processed meat and cheese, jams, and preserves. It can have potential side effects as per a study published in the Journal of Clinical Epidemiology. [3] [4]

Industrial Cleaning

The corrosive nature of phosphoric acid makes it an ideal option for cleaning off rust from industrial machinery and equipment, as suggested in a research published in the journal Electrochimica Acta. It combines with iron oxide and becomes ferric phosphate, which is very easy to remove. As per the U.S. Department of Health and Human Services, it is used in a variety of cleaning products available in the market today. [5]


The disinfectant and bactericidal qualities of phosphoric acid make it popular as an ingredient in fertilizer, which is one of the most high-volume applications of this acid. It is also included in the feed for livestock and poultry, due to its pleasant flavor. [7]


The ability of phosphoric acid to corrode porcelain makes it useful in dentistry, as it can etch and clean teeth very effectively. It may also be included in toothpaste and mouthwash liquids for its acidity, flavor, and a slight effect on tooth whitening. [8]

Dangers/Side Effects

While phosphoric is casually included in countless products we may consider, it is important to remember that this acid should only be consumed in moderation. Phosphoric acid breaks down into phosphorous in our bodies, and while this is an essential nutrient for many processes, it is possible to consume an excessive amount.

Phosphorous is needed by the body to build strong bones and teeth, and also to generate energy and ensure that our muscles function properly. It also helps our kidneys filter waste. That being said, most people get a sufficient amount of phosphorus in their diet, so an excess of this element, through the consumption of phosphoric acid, can be dangerous.

  • Increased risk of osteoporosis: An excess of phosphorus can cause a decrease in calcium, increasing your risk of osteoporosis, and some studies have also linked too much phosphorous to elevated heart disease risk. According to this study published in The Journal of Pediatrics, children who consume large amounts of phosphoric acid in soft drinks are at higher risk for hypocalcemia. [9]
  • Dangerous for people with kidney problems: On a daily basis, we only need 700 mg of phosphorus, but there can be as much as 500 mg of phosphoric acid in a single can of soda. If you are suffering from or at risk of kidney disease, you may not be able to process phosphorous normally, which could cause it to build up in your bloodstream. [10]

As a standalone chemical substance, phosphoric acid is also dangerous, and should not be inhaled or ingested. If it comes into contact with your skin or eyes, it should be rinsed off immediately, and eyes should be flushed for 10-15 minutes. Medical attention should then be sought. Despite being such a common ingredient, it still poses certain threats and should be handled carefully, and consumed in food and beverage products in moderation.

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About the Author

John Staughton is a traveling writer, editor, publisher and photographer with English and Integrative Biology degrees from the University of Illinois in Champaign-Urbana (USA). He co-founded the literary journal, Sheriff Nottingham, and now serves as the Content Director for Stain’d Arts, a non-profit based in Denver, Colorado. On a perpetual journey towards the idea of home, he uses words to educate, inspire, uplift and evolve.

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