Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas and jams, providing a tangy or sour taste. Soft drinks containing phosphoric acid, which would include Coca-Cola, are sometimes called phosphate sodas or phosphates. Phosphoric acid in soft drinks has the potential to cause dental erosion. Phosphoric acid also has the potential to contribute to the formation of kidney stones, especially in those who have had kidney stones previously.
Specific applications of phosphoric acid include:
- In anti-rust treatment by phosphate conversion coating or passivation
- As an external standard for phosphorus-31 nuclear magnetic resonance.
- In phosphoric acid fuel cells.
- In activated carbon production.
- In compound semiconductor processing, to etch Indium gallium arsenide selectively with respect to indium phosphide.
- In microfabrication to etch silicon nitride selectively with respect to silicon dioxide.
- As a pH adjuster in cosmetics and skin-care products.
- As a sanitizing agent in the dairy, food, and brewing industries.
A link has been shown between long-term regular cola intake and osteoporosis in later middle age in women (but not men). This was thought to be due to the presence of phosphoric acid, and the risk for women was found to be greater for sugared and caffeinated colas than diet and decaffeinated variants, with a higher intake of cola correlating with lower bone density.
At moderate concentrations phosphoric acid solutions are irritating to the skin. Contact with concentrated solutions can cause severe skin burns and permanent eye damage.