Sulphuric Acid is an important industrial chemical which is used in the manufacturing processes of many goods over a wide range of applications. Over one million tonnes of Sulphuric Acid are made each year in the UK alone, with an additional 40 million tonnes being produced in the USA. Annual worldwide production of Sulphuric Acid stands at around 180 million tonnes.
Sulphuric Acid is made by burning Sulphur to release Sulphur Dioxide which is then reacted with a catalyst at a high temperature. This results in Sulphur Trioxide which can be absorbed to give Sulphuric Acid. It is also formed in nature by the oxidation of Sulphide minerals such as Iron Sulphide. In certain parts of the world this gives rise to highly acidic streams which may be brightly coloured due to their toxic content.
The word often appears with a letter ‘f’ as in Sulfuric Acid and the substance is also known as Vitriol or Oil of Vitriol. Its chemical formula is H2SO4 and it appears as a clear, colourless, oily liquid with extremely corrosive properties. This acid is available in concentrated form or in dilutions, depending on its intended use.
Common Uses of Sulphuric Acid are:-
The Manufacture of Fertilisers
The major use of Sulphuric Acid is in the production of Phosphoric Acid which is used to make Phosphate fertilisers. These are added to the soil to improve plant growth. In ancient times farmers used natural fertilisers such as Nitrogen-fixing plants like clover to improve their crop yield but today modern synthetic fertilisers are widely used. Their use, however, is hotly debated with critics arguing that organically-produced foodstuffs are better for people, wildlife and the environment.
As a highly important chemical compound, Sulphuric Acid is used in the manufacturing process of a number of well-known chemicals including Hydrochloric Acid, Nitric Acid and Phosphoric Acid.
The process of refining crude oil requires the use of an acid as a catalyst and Sulphuric Acid is often used for this purpose. It is used in a SAAU or Sulphuric Acid Alkylation Unit.
‘Pickling’ is a term used to describe the treatment of metals to remove impurities, rust or scale from the surface, such as in steel making. Today, the use of Sulphuric Acid for this purpose has decreased a little as the industry now favours the use of Hydrochloric Acid. Although Hydrochloric Acid is more expensive than Sulphuric Acid, it produces results more quickly and minimises the loss of base metal during the pickling process.
The Manufacture of Rayon
The textile Rayon is made from cellulose fibres derived from wood. These are dissolved in a solution of Tetra Amine Copper (II) to produce a thick blue liquid which is then injected into Sulphuric Acid to form Rayon fibres. Rayon is considered to be a good semi-synthetic textile and can rival silk for drape and lustre. Indeed, it is sometimes referred to as ‘art silk’. It is easily dyed and the fabric is soft, cool and smooth. However, unlike silk, Rayon does not insulate body heat so is perfect for use in humid and hot countries.
The Manufacture of Lead-Acid Type Batteries
Sealed-unit lead-acid type batteries are used in the automotive industry for cars and trucks. This type of battery was invented in 1859 by Frenchman Gaston Plante and the basic design has changed remarkably little over the past 100 years ago. Sulphuric Acid is used in a dilute form to act as an electrolye to allow the flow of electrons between the plates in the battery. Sulphuric Acid used in this way is commonly called Battery Acid. It can vary in strength according to the battery manufacturer but is generally between 28 to 32% or between 4.2 to 5 Molar.
Increasingly, potato farmers employ specialist contractors to spray their fields of potatoes before harvesting so that the green tops die back and blacken within a day or two. This helps to dry out the stem and prevents them from becoming tangled in the harvesting equipment. The usual method of spraying potato tops is with a solution of Sulphuric Acid.
The Manufacture of Medicines
Chemotherapy drugs are used to treat various types of cancer. Cancer cells are more sensitive to DNA damage than normal cells so in chemotherapy treatment cancer cells are destroyed by damaging their DNA. This process is known as alkylation of DNA and a type of drug known as alkylating antineoplastic agents are used. Sulphuric Acid is used in the manufacturing process of such drugs.
In addition to the Common Uses of Sulphuric Acid listed above, it is also used in the manufacture of Cellophane, Acid dyes (where Sulphuric Acid is used to ‘fix’ colour to a fabric), Plastics, Perfumes, Paints and Disinfectants.
People wishing to buy Sulphuric Acid should be aware that it is classified as Highly Corrosive. It can cause very severe chemical burns on contact and is considered to be one of the most hazardous acids – more hazardous than Hydrochloric Acid or Nitric Acid.
Concentrated forms of Sulphuric Acid present the greatest potential danger although even dilute forms will cause burns.
Always read the MSDS (Material Safety Data Sheet) provided by your Sulphuric Acid supplier before handling the material and talk to your supplier if you have any concerns or questions.
Wear protective clothing when handling the substance including approved eye protection, compatible safety gloves, protective coveralls and safety boots. Wear a face mask when handling large quantities and work under fume extraction.