The industry produces 70,000 chemical products in 12,000 plants, with 95% in batch operations. Organic chemicals accounted for the greatest share of production (by weight) in 1997. Top five organic chemicals include ethylene, propylene, ethylene dichloride, methyl-tert-butyl-ether (MTBE), and vinyl chloride. Top inorganic chemicals produced include nitrogen, oxygen, chlorine, and sodium hydroxide. Ammonia and sulfuric acid are major agricultural chemicals used in the production of fertilizers (urea, ammonium nitrate, sulfate and phosphates, phosphoric acid). [CMA 1998]