Sulphuric acid is called the king of acids because of its importance as an industrial chemical. It is used in the manufacture of fertilizers, dyes, drugs, explosives, paints, synthetic fibres and detergents. It is also used in the manufacture of other acids such as hydrochloric acid and nitric acid. Different metals are pickled in sulphuric acid to clean them. It is also used in refining sugar and petroleum and to produce a vast range of chemicals. Do you know how this acid is manufactured?
There are two methods used to manufacture sulphuric acid. One is known as Lead Chamber Process which dates back to about 200 years. The other is known as Contact Process. The former is less efficient and complex than the latter; still it is of considerable commercial importance. In Lead Chamber Process, first sulphur dioxide is obtained by burning sulphur or roasting pyrites. Then the sulphur dioxide thus obtained is oxidized by oxides of nitrogen to get sulphur trioxide which reacts with steam to produce sulphuric acid.
Sulphuric acid is commercially manufactured by contact process. In this method the sulphur dioxide gas is mixed with air and heated with a catalyst. The catalyst is either the metal platinum or a compound called vanadium pentaoxide. The catalyst helps to quicken the reaction. The sulphur dioxide combines with the oxygen in the air to form sulphur trioxide. When sulphur trioxide is dissolved in water, it forms sulphuric acid.
Pure sulphuric acid is a heavy, oily, colourless liquid. It is very reactive and attacks most of the metals to form salts called sulphates. It quickly absorbs water and is often used as a drying agent.
While handling sulphuric acid, one should add sulphuric acid to water and not vice versa. If water is added to sulphuric acid, the heat produced causes water to boil. This makes the hot acid spit dangerously.