Phosphoric acid, also called orthophosphoric acid, is one of the most well-known and widely used acids. It is a mineral acid with the formula H3PO4, which contains one phosphorus atom, four oxygen atoms, and three hydrogen atoms. The crude form of this acid is extracted from phosphate rocks.
This compound is one of the most important chemicals that is widely used in various industries. Phosphoric acid has the highest production among acids in the world after sulfuric acid. This acid is widely used in raw materials needed to produce pharmaceuticals, Agrochemicals and pesticides, food cleaners and livestock and poultry feed supplements, and other products. Industrially, it is mostly used in the production of phosphate fertilizers. like potassium sulfate.
Physical and chemical properties:
It is a colorless, odorless, non-volatile mineral liquid that exists as a high-density liquid, miscible with water, and denser than that. When in water, it hydrolyzes and generates a lot of heat. This acid is a chelating compound and if it gets on metals, it can cause corrosion. This substance exists in both liquid and solid forms, the liquid type of which has a purity of 85%, but the solid type is completely pure and powdery.
|Molar mass||97.994 g·mol−1|
|Appearance||a clear colorless liquid or transparent crystalline solid|
|Density||1.6845 g⋅cm−3 (25 °C, 85%),
1.834 g⋅cm−3 (solid)
|Melting Point||40–42.4 °C (104.0–108.3 °F; 313.1–315.5 K)|
|Boiling point||407 °C (414 °F)|
|Solubility in water||392.2 g/100 g (−16.3 °C)
369.4 g/100 mL (0.5 °C)
446 g/100 mL (15 °C)
548 g/100 mL (20 °C)
|Solubility||Soluble in ethanol|
|Viscosity||2.4–9.4 cP (85% aq(
147 cP (100%)
|Vapor Pressure||0.03 mm Hg|
|form||Unstable orthorhombic crystals or clear syrupy liquid|
|Chemical Structure Depiction|
Structure and formula of Phosphoric acid:
The chemical formula of phosphoric acid is H3PO4 and its molecular mass is 97.99 g/ mole.
The central phosphorus atom is attached to an oxygen atom by a double bond and three hydroxyls (OH) groups by a single bond.
Types of phosphoric acid:
Based on the percentage of purity, phosphoric acid can be divided into three categories and for each of them, its specific applications can be defined.
- Industrial: This type of acid is used in the production of detergents, textile industry, wastewater treatment, and also in the production of Teflon containers.
- food: This type of acid can be produced by adding water to P2O5 or from phosphate-containing rocks in the presence of sulfuric acid. Applications of this compound include its use in the production of vegetable oils, carbonated beverages, animal feed, and animal feed supplements.
- Crude phosphoric acid: This acid is obtained from the chemical reaction between sulfuric acid and phosphate soil and is converted to food and industrial type in treatment units. It should be noted that the most common use of crude phosphoric acid is in the production of chemical fertilizers.
Phosphoric acid Production Process:
Phosphoric acid can be produced by two methods, thermal and wet. The thermal method produces products of high purity.
Phosphoric acid produced by the wet method is mostly used for the production of chemical fertilizers and animal and poultry feed, and of course, through the purification of this acid, it can be made suitable for the food grade.
- Wet process: The most common method of producing phosphoric acid in the world is more methodical.
From the combination of iron ore and concentrated sulfuric acid (93%) in the reactor, impurities such as calcium are removed.
- Thermal process: Phosphorus is converted to phosphorus oxide in the presence of excess air. This oxide produces phosphoric acid by absorbing heat from the fuel and being hydrated.
5O2 + P4(l) → 2P2O5 (g)
P2O5 (g) + 3H2O(l) → 2H3PO4(l)
Applications and Uses of Phosphoric acid:
This compound is one of the most important chemicals that is widely used in various industries, including agriculture and the products we use in our daily lives. This substance is one of the most important and useful mineral acids and is also used in the food industry.
- Acidity regulator in foods such as jams, processed meats, jellies and gelatins, yeasts, cheeses, spices, condiments, and preserves.
- Food additives in the food industry;
- In the production of beverages;
- Livestock and poultry industries;
- In personal care products;
- Elimination of mineral deposits;
- Dyes and pigments;
- Fertilizer and phosphate fertilizer industry;
- Remove iron rust;
- In agriculture;
- In the water and wastewater treatment industry.
Usage of Industrial Phosphoric acid in Agriculture:
Fertilizer is an essential nutrient for plant growth and health. One of the substances used as fertilizer in agriculture is phosphoric acid. This acid is made from a combination of three elements: phosphorus, oxygen, and hydrogen. About 80% of the phosphoric acid produced in the world is used to make fertilizer.
This substance is mainly converted into three phosphate salts which are used as fertilizers. They are triple superphosphate (TSP), diammonium phosphate (DAP), and monoammonium phosphate (MAP).
The use of phosphoric acid in fertilizers reduces the use of pesticides and reduces the cost of using pesticides.
Properties of phosphoric acid for plant growth:
- It is essential for photosynthesis in plants;
- Increases root growth;
- It absorbs and converts solar energy into plant materials;
- Increases plant resistance to various factors;
- Increases the quality and speed of plant production;
- Improves the formation of flowers and seeds in the plant;
- Increases the strength of stems and branches.
Today, most agricultural soils face the problem of phosphorus deficiency and thus reduce crop production, while in some areas there is excess phosphorus. Of course, the problem of soil phosphorus deficiency is exacerbated by continuous cultivation and soil erosion.
Therefore, the use of phosphoric acid in agriculture is a great option to strengthen plants and get more products from them.
Phosphoric acid can be very hazardous in the case of skin contact, eye contact, and ingestion. It can also cause irritation if vapors are inhaled. This chemical can cause damage to the skin, eyes, mouth, and respiratory tract.
Packing and storage:
Store in a cool, with proper ventilation, and keep away from incompatible substances such as oxidizing agents, metals, combustible materials, and alkalis.