What is chloroform?

Chloroform is a toxic, sweet-smelling, colorless liquid.

Chloroform, also known as trichloromethane, is a colorless, sweet-smelling liquid with the chemical formula CHCl 3 . It is best known for its historical use as a general anesthetic, although it has since been abandoned for safety reasons. Today, trichloromethane is used in a variety of industrial processes, including the manufacture of plastics, refrigerants and solvents. It is found in small amounts in water and the atmosphere; most of this comes from natural sources. Chloroform is toxic and releases vapor quickly when exposed to air, so it must be handled with care.


People who work with chloroform in industrial applications can wear protective clothing to avoid the risks of chronic exposure.

This compound was originally made by reacting ethanol or acetone with bleaching powder – calcium hypochlorite. In modern times, however, it is manufactured industrially by combining methane with chlorine. Small amounts of the chemical are naturally produced by marine life, such as algae, and by the decomposition of plant debris in the soil. The main human sources in the environment are the use of chlorine as a bleaching agent in paper mills and the chlorination of drinking water. Chlorine reacts with various organic compounds to produce trichloromethane, but the amounts present in chlorinated water are minuscule and are not believed to pose any risk to human health under normal circumstances.


Long-term exposure to low concentrations of trichloromethane can have adverse effects on the kidneys.

The use of chloroform as an anesthetic dates back to 1847, but concerns about its safety soon arose. In 1848, a patient died because her heart beat fast and irregularly while she was anesthetized, and continued use only cemented the link between the chemistry and cardiac events. In the early 20th century, the use of chloroform was in decline and was abandoned in favor of safer, cheaper alternatives around 1940. Today, safer anesthetics such as halothane, isoflurane, and sevoflurane, among others, are used. When a less expensive alternative is needed, as is the case in some impoverished countries, ether, an older anesthetic, is often preferred.

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Chloroform adversely affects major organs – including the heart, liver and kidneys – which makes it dangerous as an anesthetic.

Today, chloroform’s biggest use is in the production of polytetrafluoroethylene (PTFE), a relatively heat-resistant plastic best known for its use as a nonstick coating for pots and pans. The compound is first reacted with hydrogen fluoride to form chlorodifluoromethane, a compound used as a refrigerant and propellant for aerosol cans. This use has been discontinued in many countries due to its effects on the ozone layer, but its production is still an important step in the manufacture of PTFE.

In the laboratory, trichloromethane is often used as a solvent, as it is stable, relatively unreactive, and dissolves many organic compounds. It is very effective in extracting substances from plant material and is used in this way in the pharmaceutical industry to extract drugs and drug precursors from plants. It can also be used in analytical chemistry to isolate compounds from samples and is used in the synthesis of many organic chemicals.

health effects

The anesthetic effects of chloroform are well known and are due to inhibition of central nervous system activity. Inhalation of the vapor can quickly cause unconsciousness, but too high a dose can be fatal. The chemical also affects the activity of other important organs, including the heart, which makes it dangerous as an anesthetic. It is considered moderately toxic – in terms of acute effects – if ingested, but a dose of 0.35 fluid ounces (10 milliliters) can be fatal in humans.

Long-term exposure to relatively low concentrations of trichloromethane can have a number of adverse effects, especially on the liver and kidneys. There may be a risk of cancer associated with exposure to this chemical. While there is no conclusive evidence of a link to cancer in humans, animal tests have shown that chloroform can cause liver and kidney tumors, and in the US, the Environmental Protection Agency (EPA) has classified it as a “likely human carcinogen”. Exposure is most likely to occur in an industrial or laboratory environment, but small amounts are present in the atmosphere and water. As it does not react with many naturally occurring substances, it can take a long time to decompose and can accumulate in groundwater.

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Another potential risk in the handling and storage of chloroform is the formation of the highly toxic gas, phosgene, which was used as a chemical weapon during World War I. In the presence of light, trichloromethane reacts with oxygen in the air to produce this gas . For this reason, it is stored in dark glass bottles.

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