dr.CHEMIST

                     INTRODUCTION      

      <THE HISTORY OF SULPHURIC ACID>

The discovery of sulphuric acid is credited to the 8^0th century Arabian chemist an alchemist, Jabir ibn Hayyan(Geber). The acid was later studied by 9^th century Persian physician and alchemist Ibn Zakariya al-Razi(Rhazes), who obtained the substance by dry distillation of minerals including iron(II) sulphate heptahydrate FeSO4 • 7H2O, and copper sulphate pentahydrate, CuSO4  • 5H2O.When heated, these compounds decompose to iron(II) oxide and copper(II) oxide, respectively, giving off water and sulphur trioxide, which combine to produce a dilute solution of sulphuric acid. This method was popularized in Europe through translations of Arabic and Persian treatises, as well as books by European alchemist, such as the  13^th-century German Albertus Magnus.

Sulphuric acid was known to medieval European alchemist as oil of vitriol, spirit of vitriol, or simply vitriol, among other names. The word vitriol derives from the Latin vitreus, ‘glass’, referring to the glassy appearance of the sulphate salts, which also carried the name vitriol. Salts called by this name included copper(II) sulphate (blue vitriol, or rarely Roman vitriol), zinc sulphate (white vitriol), iron(II) sulphate (green vitriol), iron(III) sulphate (vitriol of Mars), and cobalt(II) sulphate (red vitriol).

Vitriol was widely considered the most important alchemical substances, intended to be used as a philosopher’s stone. Highly purified vitriol was used as a medium for reacting other substances. This was largely because the acid does not react with gold, production of which was often the final goal of alchemical processes. The important of vitriol to alchemy is highlighted in the alchemical motto, Visita Interiora Terrae Rectificando Invenies Occultum Lapidem which is a backronym meaning (‘Visit the interior of the earth and rectifying (i.e. purifying) you will find the hidden/ secret stone’), found in L’Azoth des Philosophes by the 15^th century alchemist Basilius Valentinus 

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

In 1746 in Birmingham, John Roebuck adapted this method to produce sulphuric acid in led-lined chamber, which were stronger, less expensive, and could be made larger than the previously use glass containers. This lead chamber  processes allowed the effective industrialization of sulphuric acid production. After several refinements, this method remained the standard for sulphuric acid production almost two centuries.

Sulphuric acid created by John Roebuck’s process only approached a 35-40% concentration. Later refinements to the lead-chamber process by French chemist Joseph-Louis Gay-Lussac and British chemist John Glover improved the yield to 78%. However, the manufacture of some dyes and other chemical processes require a more concentrated product. Throughout the 18^th 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) sulphate, FeSO4, which was oxidized by further heating air to form iron(III) sulphate, Fe2(SO4)3, which when heated to 480˚C, decomposed to iron(III) oxide and sulphur trioxide, which could be passed through water to yield sulphuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulphuric acid.

In 1831, British vinegar merchant Peregrine Phillips patented the contact process, which was a far more economical process for producing sulphur trioxide and concentrated sulphuric acid. Today, nearly all of the world’s sulphuric acid is produced using this method.