Sulfuric acid Guide, Meaning , Facts, Information and Description

Sulfuric acid (British English: Sulphuric), H₂SO₄, is a strong mineral acid (not an organic acid). It can form any concentration in water. The old name for sulfuric acid is oil of vitriol. When high concentrations of SO₃ are added when making the acid, a solution of SO₃ in H₂SO₄ results. This is called fuming sulfuric acid or Oleum or Nordhausen acid.

Sulfuric acid has many applications, including in many chemical reactions and production processes. It is the most widely used chemical. Principal uses include fertilizer manufacturing, ore processing, chemical synthesis, wastewater processing and oil refining.

In combination with nitric acid it forms the nitronium ion, which is used in the nitration of compounds. The process of nitration is used to manufacture a great many explosives, including trinitrotoluene, nitroglycerine, and guncotton. It is also the acid used in lead-acid batteries, and so is sometimes known as battery acid.

The hydration reaction of sulfuric acid is highly exothermic. If water is added to concentrated sulfuric acid, it can boil. Always add the acid to the water rather than the water to the acid. Note that part of this problem is due to the relative densities of the two liquids. Water is less dense than sulfuric acid and will tend float above the acid.

Because the hydration of sulfuric acid is thermodynamically favorable, sulfuric acid is an excellent dehydration 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 molecules out of other compounds; for example, mixing glucose (C₆H₁₂O₆) and concentrated sulfuric acid will give elemental carbon and water which is absorbed by the sulfuric acid (which becomes slightly diluted): C₆H₁₂O₆ --> 6C + 6H₂O.

When in the atmosphere it is part of many chemicals which make up acid rain.

History of sulfuric acid

The discovery of sulfuric acid is credited to the 9th century Islamic physician and alchemist Ibn Zakariya al-Razi (Rhases), who obtained the subtance by dry distillation of minerals including iron (II) sulfate heptahydrate, FeSO₄ • 7 H₂O, called green vitriol, and copper (II) sulfate pentahydrate, CuSO₄ • 5 H₂O, called blue vitriol. When heated, these compounds decompose to iron and copper oxides, respectively, giving off water and sulfur trioxide, which combine to produce a dilute solution of sulfuric acid. This method was popularized in Europe through translations of Islamic treatises and books by European alchemists, such as the 13th-century German Albertus Magnus. For this reason, sulfuric acid was known to medieval European alchemists as oil of vitriol and spirit of vitriol, among other names.

In the 17th century, the German-Dutch chemist Johann Glauber prepared sulfuric acid by burning sulfur together with saltpeter (potassium nitrate, KNO₃), in the presence of steam. As the saltpeter decomposes, it oxidizes the sulfur to SO₃, which combines with water to produce sulfuric acid. In 1736, Joshua Ward, a London pharmacist, used this method to begin the first large-scale production of sulfuric acid.

In 1746 in Birmingham, John Roebuck began producing sulfuric acid this way in lead-lined chambers, which were stronger, less expensive, and could be made larger than the glass containers which had been used previously. This lead chamber process allowed the effective industrialization of sulfuric acid production, and with several refinements remained the standard method of production for almost two centuries.

John Roebuck's sulfuric acid was only about 35-40% sulfuric acid. Later refinements in the lead-chamber process by the French chemist Joseph-Louis Gay-Lussac and the British chemist John Glover improved this to 78%. However, the manufacture of some dyes and other chemical processes require a more concentrated product, and throughout the 18th century, this could only be made by dry distilling minerals in a technique similar to the original alchemical processes. Pyrite (iron disulfide, FeS₂) was heated in air to yield iron (II) sulfate, FeSO₄, which was oxidized by further heating in air to form iron (III) sulfate, Fe₂(SO₄)₃, which when heated to 480°C decomposed to iron (III) oxide and sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. The expense of this process prevented the large-scale use of concentrated sulfuric acid.

In 1831, the British vinegar merchant Peregrine Phillips patented a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. In this process sulfur dioxide, SO₂, produced by roasting either sulfur or pyrite in air, is combined with additional air and passed over a platinum catalyst at high temperatures, where it combines with oxygen from the air to produce nearly pure SO₃. Even so, there was little demand for highly concentrated sulfuric acid at the time, and the first sulfuric acid plant using this contact process was not built until 1875 in Freiburg, Germany.

The development of the less expensive and less easily contaminated vanadium pentoxide (V₂O₅) catalyst by BASF in Gemany in 1915, combined with increasing demand for concentrated sulfuric acid by the chemical industry, has led to the gradual replacement of the lead-chamber process by the contact process. In 1930, sulfuric acid produced by the contact process accounted for only 25% of sulfuric acid production, while today nearly all sulfuric acid is manufactured in this way.

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