Lime is also an important material in the manufacture of chemicals. Its major use here is in the production of calcium carbide, CaC 2 . Calcium carbide is manufactured by heating lime with coke. Acetylene is an important fuel for welding and is also a starting material for a range of organic compounds, including vinyl chloride, neoprene, and acrylonitrile, all of which are raw materials for polymers. Pollution control is a rapidly expanding consumer of lime.
Lime is used in stack gas scrubbers to reduce sulfur dioxide emissions from power plants.
Sulfur dioxide reacts with lime to form solid calcium sulfite. Lime is also added to sewage to remove phosphates. The pretreatment of water supplies involves the use lime to decrease the acidity, to soften, and to clear drinking water. A variety of other industrial processes also make extensive use of lime. It is used as an opacifier in plastics.