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Phosphoric acid

Phosphoric acid, also known as orthophosphoric acid or simply phosphoric acid, is a weak acid with the chemical formula H₃PO₄. It is commonly found as a colorless liquid with a concentration of 85% in water. All three hydrogen atoms in the molecule exhibit different levels of acidity and can dissociate as H⁺ ions (protons). When all three H⁺ ions are removed, the resulting ion is orthophosphate (PO₄³⁻), typically referred to as “phosphate.”

Description

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Phosphoric acid, also known as orthophosphoric acid or simply phosphoric acid, is a weak acid with the chemical formula H₃PO₄. It is commonly found as a colorless liquid with a concentration of 85% in water. All three hydrogen atoms in the molecule exhibit different levels of acidity and can dissociate as H⁺ ions (protons). When all three H⁺ ions are removed, the resulting ion is orthophosphate (PO₄³⁻), typically referred to as “phosphate.”

In laboratories, phosphoric acid is usually available as an 85% aqueous solution, which is a colorless, odorless, and non-volatile liquid. While phosphoric acid does not meet the strict definition of a strong acid, the 85% solution can still cause significant skin irritation and damage to the eyes. To distinguish this specific acid from other “phosphoric acids,” such as pyrophosphoric acid, the term “orthophosphoric acid” is sometimes used. However, “phosphoric acid” typically refers to this compound.

Industrial Uses of Phosphoric Acid:

Phosphoric acid finds extensive commercial use in a variety of applications apart from fertilizers, including detergents, food processing, dental products, metal surface cleaners, and more.

Market and Applications of Phosphoric Acid

Phosphoric acid has a wide range of applications, leading to a diverse and broad market. Its most significant use is in agriculture for producing fertilizers, accounting for nearly 90% of its global production. Additionally, phosphoric acid is frequently employed to impart a tangy flavor to food products. Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages like colas and jams, giving them a sour taste.

Soft drinks containing phosphoric acid, including Coca-Cola, are sometimes referred to as “phosphate sodas.” Phosphoric acid, produced by Padid Avandegan Jam Company, has gained a solid position in both domestic and international markets due to its high quality and competitive price.

Common Applications of Phosphoric Acid

1. As a Food Additive

Phosphoric acid is widely used in the food industry to prepare acidic foods and carbonated beverages, such as colas. Its tangy flavor and affordability make it a popular choice over natural flavorings like ginger for spiciness or citric acid for sourness.

2. As a Cleaner in Medicine and Dentistry

Phosphoric acid is used in dentistry and orthodontics as a cleaning agent for enamel and dentin, enhancing friction and abrasion. Additionally, its high hydrogen ion concentration and lower contamination compared to hydrochloric and sulfuric acids make it a preferred catalyst in aspirin manufacturing.

In medicine, phosphoric acid is known as orthophosphoric acid, and its salts, called orthophosphates, are used as a primary treatment for kidney stones.

3. In Agriculture

The primary use of phosphoric acid is in the production of agricultural fertilizers. Phosphorus is an essential element for plant growth as it provides energy for most cellular reactions. Soils rich in phosphates significantly enhance plant growth. However, excess phosphates in water can promote the overgrowth of aquatic plants, leading to environmental risks such as oxygen depletion, which can harm aquatic life.

To mitigate this, alternatives to phosphate-based cleaners are increasingly used, which do not react with calcium, magnesium, or hard water ions, reducing environmental phosphate pollution.

4. Rust Removal

Phosphoric acid can be directly used to remove rust (iron oxide) from steel or iron tools. After rust removal, the resulting iron phosphate acts as an anti-corrosion agent.

5. Catalyst in Chemical Industries

Phosphoric acid is used as a catalyst in petrochemical industries.

MSDS (Material Safety Data Sheet) for Phosphoric Acid

Below is a summary of the key sections from the MSDS for phosphoric acid:

Section Information
Chemical Identification Phosphoric Acid (H₃PO₄), CAS Number: 7664-38-2
Physical State Colorless, odorless liquid
Hazards Identification Can cause severe skin irritation, eye damage, and respiratory issues
Handling and Storage Store in a cool, dry, well-ventilated area away from incompatible substances
First Aid Measures Skin Contact: Wash with plenty of soap and water
Eye Contact: Rinse immediately with water for 15 minutes, seek medical help
Inhalation: Move to fresh air, seek medical attention if symptoms persist
Ingestion: Do not induce vomiting, rinse mouth, and seek medical advice
Firefighting Measures Non-flammable; use water spray, dry powder, or foam for extinguishing nearby fires
Personal Protection Wear gloves, safety goggles, and a lab coat
Spill Handling Neutralize with a base like sodium bicarbonate; use absorbent material
Toxicology Information May cause burns, respiratory irritation, or long-term organ damage with prolonged exposure

 

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