Chloroform (CHCl3), also known as chloroform, is a nonflammable, clear, colorless liquid that is denser than water and has a pleasant ether-like odor. It was first formulated in 1831. It was first used as an anesthetic in 1847 by Scottish physician Sir James Simpson of the University of Edinburgh. It was brought to public attention in 1853 by British physician John Snow, who used it at the birth of Queen Victoria. Her eighth child, Prince Leopold.

chloroform formula has a relatively narrow safety margin and has been superseded by better inhalational anesthetics. Additionally, it is considered toxic to the liver and kidneys and may cause liver cancer. Chloroform was once widely used as a solvent, but safety and environmental concerns have curtailed this use. Nonetheless, chloroform remains an important industrial chemical.

Chloroform is prepared by chlorination of methane. The main use of chloroform is in the preparation of chlorodifluoromethane (HCFC-22). HCFC-22 depletes the ozone layer, and the U.S. plans to stop production by 2020. Chloroform production is expected to drop significantly as HCFC-22 production is phased out.
Chloroform is formed by the reaction of chlorine with organic substances present in the water and therefore may be present in chlorinated drinking water. The U.S. Environmental Protection Agency has set a limit of 80 parts per billion (ppb) for chloroform contamination; typical municipal water supplies contain about 50 ppb.
Due to their high reactivity, free halogen elements do not occur in nature. In compound form, fluorine is the most abundant halogen in the earth's crust. The percentages of halogens in crustal igneous rocks are 0.06 fluorine, 0.031 chlorine, 0.00016 bromine and 0.00003 iodine. Astatine and Tennessee stars do not exist in nature because they consist only of short-lived radioactive isotopes