Phosphoric acid or orthophosphoric acid, chemical formula H3PO4, molecular weight 97.994, is a common inorganic acid, is a medium strong acid. It can be obtained by dissolving phosphorus pentoxide in hot water. Orthophosphoric acid is obtained by treating apatite with sulfuric acid in the industry. Phosphoric acid is easily deliquescent in the air. Heating will lose water to get pyrophosphoric acid, and further lose water to get metaphosphoric acid. Phosphoric acid is mainly used in pharmaceutical, food, fertilizer and other industries, including as rust inhibitor, food additive, dental and orthopedics, EDIC corrosive, electrolyte, flux, dispersant, industrial corrosive, fertilizer raw material and component household cleaning products. It can also be used as a chemical reagent. Phosphate is a nutrient for all life forms.
Material structure
Orthophosphoric acid is a phosphoric acid composed of a single phosphorous oxygen tetrahedron. In the phosphoric acid molecule, the P atom is sp3 hybridized. The 3 hybrid orbitals form 3 σ bonds with the oxygen atom. The other P—O bond consists of a σ coordination bond from phosphorus to oxygen and two σ bonds from oxygen to oxygen. Phosphorus is composed of d-pπ bonds. The σ coordination bond is formed by the coordination of a lone pair of electrons on the phosphorus atom to the empty orbital of the oxygen atom. The d←p coordination bond is formed by overlapping two pairs of lone pairs of electrons on the py and pz orbitals of the oxygen atom and the dxz and dyz empty orbitals of the phosphorus atom. Since the 3d energy level of the phosphorus atom is much higher than the 2p energy level of the oxygen atom, the composed molecular orbital is not very effective, so the P—O bond is a triple bond in terms of number, but it is a medium in terms of bond energy and bond length. Between a single bond and a double bond. Both pure H3PO4 and its crystal hydrates have hydrogen bonds, which may be the reason why the concentrated phosphoric acid solution is viscous.
Security protection
Phosphoric acid has no strong oxidizing property and no strong corrosiveness. It is a relatively safe acid, low toxicity, and irritating.
LD50: 1530mg/kg (rat oral); 2740mg/kg (rabbit skin)
Irritation: rabbit skin 595mg/24 hours, severe irritation; rabbit eyes 119mg severe irritation.
When contacting, pay attention to prevent getting into the eyes, prevent contact with the skin, and prevent the entrance.
It is flammable in contact with H porogen; it emits toxic phosphorus oxide smoke when heated.
Phosphoric acid vapor can cause nasal mucosal atrophy; it has a strong corrosive effect on the skin and can cause skin inflammatory diseases; it can cause systemic poisoning.
If phosphoric acid vapor enters the eyes, flush them with a large amount of normal saline immediately, and then send them to the hospital for treatment
　　 The maximum allowable concentration in the air is 1mg/m. Production personnel should wear protective equipment when working, such as overalls, rubber gloves, rubber or plastic aprons, and long rubber boots. Pay attention to protect the respiratory organs and skin. If accidentally splashed on the skin, rinse immediately with plenty of water. After washing the phosphoric acid, you can generally apply mercurochrome solution or gentian violet solution to the affected area. If it is severe, you should immediately send it to the hospital for treatment.
Application area
Agriculture: Phosphoric acid is the raw material for the production of important phosphate fertilizers (superphosphate, potassium dihydrogen phosphate, etc.), as well as the raw material for the production of feed nutrients (calcium dihydrogen phosphate).
Industry: Phosphoric acid is an important chemical raw material, and its main functions are as follows:
Treat the metal surface to form an insoluble phosphate film on the metal surface to protect the metal from corrosion.
Mixed with nitric acid as a chemical polishing agent to improve the smoothness of the metal surface.
Phosphate esters as raw materials for the production of detergents and pesticides.
Raw material for the production of phosphorus-containing flame retardants.
Food: Phosphoric acid is one of food additives. It is used as a sour agent and yeast nutrient in foods. Cola contains phosphoric acid. Phosphate is also an important food additive and can be used as a nutritional enhancer.
Medicine: Phosphoric acid can be used to prepare phosphorus-containing drugs, such as sodium glycerophosphate.