Sulfuric acid H2SO4, is a strong mineral acid. It is soluble in water at all concentrations. It was once known as oil of vitriol, coined by the 8th-century Alchemist Jabir ibn Hayyan, the chemical’s probable discoverer. Principal uses include ore processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis.

Know more interesting facts about Sulfuric acid by reading By Pritish Kumar Halder article below:

Systematic name Sulfuric acid (Sulphuric acid)
Other names Oil of Vitriol
Molecular formula H2SO4 (aq)
Molar mass 98.08 g/mol
Appearance Clear, colorless, odorless liquid
CAS number [7664-93-9]
Density and phase 1.84 g/cm3, liquid
Solubility in water Fully miscible
Melting point 10°C (283 K)
Boiling point 337°C (610 K)


Structure of Sulfuric Acid

 Polarity and conductivity

Anhydrous H2SO4 is a very polar liquid, with a dielectric constant of around 100. This is due to the fact that it can dissociate by protonating itself, a process known as autoproteolysis, which occurs to a high degree, more than 10 billion times the level seen in water:

2 H2SO4 ⇌ H3SO4+ + HSO4−

Chemical properties

Reaction with water

The hydration reaction of sulfuric acid is highly exothermic. If water is added to concentrated sulfuric acid, it can boil and spit dangerously. One should always add the acid to the water rather than the water to the acid. This can be remembered through mnemonics such as “Always do things as you oughta, add the acid to the water .The reaction is best thought of as forming hydronium ions.

H2SO4 + H2O → H3O+ + HSO4-

And then:


HSO4- + H2O → H3O+ + SO42-

Because the hydration of sulfuric acid is thermodynamically favourable ( ΔH = -880 k J/ mol), sulfuric acid is an excellent dehydrating agent, and is used to prepare many dried fruits. The affinity of sulfuric acid for water is sufficiently strong that it will take hydrogen and oxygen atoms out of other compounds.

For example, mixing starch (C6H12O6)n and concentrated sulfuric acid will give elemental carbon and water which is absorbed by the sulfuric acid (which becomes slightly diluted): (C6H12O6)n → 6C + 6H2O. The effect of this can be seen when concentrated sulfuric acid is spilled on paper; the starch reacts to give a burned appearance, the carbon appears as soot would in a fire. A more dramatic illustration occurs when sulfuric acid is added to a tablespoon of white sugar in a cup when a tall rigid column of black porous carbon smelling strongly of caramel emerges from the cup.

Environmental aspects

Sulfuric acid is a constituent of acid rain, being formed by atmospheric oxidation of sulfur dioxide in the presence of water – i.e. oxidation of sulfurous acid. Sulfur dioxide is the main product when the Sulphur in sulfur-containing fuels such as coal or oil is burned.


Sulfuric acid is produced from sulfur, oxygen and water via the contact process.

In the first step, sulfur is burned to produce sulfur dioxide.

(1) S( s) + O2(g) → SO2(g)

This is then oxidized to sulfur trioxide using oxygen in the presence of a vanadium(V) oxide catalyst.

(2) 2 SO2 + O2(g) → 2 SO3(g)     (in presence of V2O5)

Finally the sulfur trioxide is treated with water (usually as 97-98% H2SO4 containing 2-3% water) to produce 98-99% sulfuric acid.

(3) SO3(g) + H2O( l) → H2SO4(l)

Note that directly dissolving SO3 in water is impractical due to the highly exothermic nature of the reaction. Mists are formed instead of a liquid. Alternatively, the SO3 is absorbed into H2SO4 to produce oleum (H2S2O7), which is then diluted to form sulfuric acid.

(3) H2SO4( l) + SO3 → H2S2O7(l)

Oleum is reacted with water to form concentrated H2SO4.

(4) H2S2O7(l) + H2O(l) → 2 H2SO4(l)


The major use (60% of total worldwide) for sulfuric acid is in the “wet method” for the production of phosphoric acid, used for manufacture of phosphate fertilizers as well as trisodium phosphate for detergents. This is treated with 93% sulfuric acid to produce calcium sulfate, hydrogen fluoride (HF) and phosphoric acid. The HF is removed as hydrofluoric acid. The overall process can be represented as:

Ca5F(PO4)3 + 5 H2SO4 + 10 H2O → 5 CaSO4·2 H2O + HF + 3 H3PO4

Another important use for sulfuric acid is for the manufacture of aluminum sulfate, also known as papermaker’s alum, Aluminum sulfate is made by reacting bauxite with sulfuric acid:

Al2O3 + 3 H2SO4 → Al2(SO4)3 + 3 H2O

Sulfuric acid is used for a variety of other purposes in the chemical industry.