Sulfuric Acid: Uses, Concentrations and SDS Essentials

Sulfuric acid (spelled sulphuric acid in British English) has the formula H2SO4 and CAS number 7664-93-9. It is made in larger quantities than any other chemical, and its consumption is often used as a rough indicator of industrial activity. It is a dense, oily, colourless to slightly brown liquid that is strongly acidic, a powerful dehydrating agent and, when concentrated, a strong oxidiser.

Where sulfuric acid is used

• Phosphate fertiliser production, the single largest use, by reacting phosphate rock to make phosphoric acid and superphosphate.
• Lead-acid batteries, where dilute sulfuric acid (around 30 to 40 percent) is the electrolyte.
• Metal processing, including pickling steel, leaching copper and zinc ores, and electroplating baths.
• Chemical manufacturing: sulphates, hydrochloric and nitric acid production, dyes, explosives and detergents (sulfonation).
• Petroleum refining, as the catalyst in alkylation units.
• Water treatment, for pH control, and the production of aluminium sulphate.
• Laboratories and drain-cleaning products.

Concentration grades

Commercial sulfuric acid is usually sold at roughly 93 to 98 percent (concentrated), around 78 percent and 65 percent (intermediate grades), and as battery acid at a lower strength. Oleum, which is sulfuric acid containing dissolved sulphur trioxide, is a more hazardous fuming product with its own classification and transport entry. The concentration you sell must appear in Section 3 of the SDS, and every grade should be treated as a separate product when the classification changes.

Hazard classification

Sulfuric acid is classified as causing severe skin burns and eye damage (skin corrosion category 1A, H314) with the signal word Danger and the corrosion pictogram (GHS05). The harmonised entry carries specific concentration limits, so diluted solutions below roughly 5 percent are typically classified as irritants (H315, H319) rather than corrosive, and below about 1.5 percent may fall out of classification altogether. Confirm the limits in the current CLP Annex VI entry before labelling a diluted product.

Dilution and handling safety

The rule every worker must know is to add acid slowly to water, never water to acid. Mixing generates a great deal of heat and can cause violent boiling and splashing. Use goggles and a face shield, acid-resistant gloves and apron, and work with good ventilation. Concentrated acid chars organic material such as wood, paper and skin, so cleaning up spills with sawdust or rags is dangerous.

Storage and incompatibilities

Store in acid-resistant tanks or containers, such as steel for concentrated acid and plastic or lined vessels for dilute acid, because dilute sulfuric acid attacks many metals and releases hydrogen. Keep it separated from bases, organic materials, cyanides, sulphides, chlorates and permanganates. Section 10 of your SDS should list these. Our storage compatibility guide covers segregation in more detail.

Transport and documents

Sulfuric acid is a Class 8 corrosive for transport, with separate entries for acid above and below a stated concentration, and for spent acid. Check the current UN number, proper shipping name and packing group with your carrier. On the label, show the signal word, the corrosion pictogram, the hazard and precautionary statements, and your supplier details. You can see the harmonised data we hold on the sulfuric acid page.