A major economic manufacturing sector responsible for the development and mass production of chemicals. Early nineteenth-century processes included the mass production of alkalis and, in particular, soda ash, caustic soda, and bleach. By the end of that century, various metals were being extracted from ores in large-scale processes, along with sulphuric and nitric acid, explosives, and fertilizers. The Haber process in the early twentieth century led to the production of fertilizers and radical changes in agricultural practices through the fixation of nitrogen. After the First World War, the rapid rise of the automotive industry resulted in the demand for petroleum and petroleum products including thermoplastics. The Second World War spurred the development of chemical products such as synthetic rubber, and the decades that followed led to new plastics such as polyester, polyvinylchloride, and polypropylene. The first decades of the twenty-first century are marked by the development of pharmaceutical production and with new and innovative food products.