Phosphoric acid is a colorless, odorless, inorganic chemical compound with the formula H3PO4. It is commonly encountered as an 85% aqueous solution, which is a colorless, odorless, syrupy liquid. It is an important industrial chemical and is a component of many fertilizers. Phosphoric acid is a triprotic acid and can form esters called organophosphates. It is also known as orthophosphoric acid or monophosphoric acid and can be used to distinguish it from other “phosphoric acids.”
Phosphoric acid is produced by two main methods: the wet process and the dry process.
The wet process involves treating a phosphate-containing mineral such as calcium hydroxyapatite or fluorapatite with sulfuric acid to produce a solution of phosphoric acid and calcium sulfate (gypsum). The resulting solution contains 23-33% P2O5 (32-46% H3PO4) and can be further concentrated to produce commercial or merchant-grade phosphoric acid with a concentration of 54-62% P2O5 (75-85% H3PO4).
In the dry process, phosphate ore is reduced with coke in an electric arc furnace to produce elemental phosphorus, which is distilled and burned with air to produce high-purity phosphorus pentoxide. This substance is then dissolved in water to produce food-grade phosphoric acid.
Both methods may also require purification steps to remove impurities such as arsenic and other toxic elements.
Phosphoric acid is used in a variety of applications, including:
- Food and Beverage Industry: Phosphoric acid is used as an acidifier and flavor enhancer in the production of soft drinks and fruit juices.
- Agriculture: Phosphoric acid is an important component in the production of fertilizers, as it provides essential phosphorous to crops.
- Dental Care: Phosphoric acid is used in some dental treatments as an etching agent to prepare teeth for bonding.
- Metal Cleaning: Phosphoric acid is used for rust removal and as a metal surface cleaner in various industries.
- Water Treatment: Phosphoric acid is used in water treatment to adjust the pH of water and to remove impurities.
- Pharmaceuticals: Phosphoric acid is used as a starting material in the production of some pharmaceuticals, such as antacids.
- Oil Refining: Phosphoric acid is used in the refining of petroleum products to neutralize impurities.
Phosphoric acid is a highly corrosive inorganic acid that can cause severe burns and injury if it comes in contact with skin or eyes. It is also toxic if ingested in large quantities. Inhalation of phosphoric acid fumes can irritate the respiratory system and cause coughing, shortness of breath, and other respiratory symptoms.
Handling of phosphoric acid should be done with care, wearing personal protective equipment such as gloves, goggles, and appropriate clothing. Proper storage and labeling of the chemical is also important to ensure safe handling.
In industrial settings, proper ventilation and exhaust systems are important to minimize exposure to phosphoric acid fumes. If a spill occurs, it should be cleaned up immediately using appropriate safety measures and materials.
It is also important to follow all relevant regulations and guidelines for the handling and disposal of phosphoric acid, to minimize the potential for harm to human health and the environment.