Sulfuric acid: Properties and applications

What are the key physical and chemical properties of sulfuric acid?

Sulfuric acid (H₂SO₄) is a colourless, odourless, viscous liquid with a high density and strong hygroscopic nature. It is a diprotic acid, meaning it can donate two protons, and is highly exothermic when diluted with water. Its high affinity for water makes it an effective dehydrating agent. It is produced industrially via the contact process and is classified as a Tier 1 chemical under REACH and GHS due to its corrosive and hazardous nature. It is also used in analytical chemistry for sample digestion and in the purification of petroleum products.

How is sulfuric acid used in industrial and laboratory settings?

In industry, over 90% of sulfuric acid production is used in the manufacture of phosphate fertilisers, such as ammonium sulfate and superphosphate. It is also essential in the production of chemicals including aluminium sulfate, synthetic detergents, and dyes. In laboratories, it serves as a catalyst in esterification reactions, a reagent in organic synthesis, and a standard in titrations. In battery technology, it is the electrolyte in lead-acid batteries. Due to its reactivity, it must be handled with appropriate PPE and stored in corrosion-resistant containers, typically made of lead or polyethylene.

What safety and regulatory considerations apply?

Sulfuric acid is classified as corrosive (GHS H290) and poses significant health and environmental risks. It requires compliance with ISO 14001, REACH, and TSCA regulations. Safety data sheets (SDS) and certificates of analysis (CoA) are mandatory for procurement. Proper ventilation, spill containment, and neutralisation protocols are essential in handling.

Related concepts

Sulfuric acid is often used alongside other strong acids such as hydrochloric acid (HCl) and nitric acid (HNO₃). Its industrial significance is mirrored in its use in analytical techniques like HPLC and GC-MS for sample preparation.