Chloroform

Properties

General
Name	Chloroform
Chemical formula	CHCl3
Appearance	Colourless liquid
Physical
Formula weight	119.4 amu
Melting point	210 K (-63 °C)
Boiling point	335 K (61 °C)
Density	1.48 ×103 kg/m3 (liquid)
Solubility	slightly soluble in water
Thermochemistry
ΔfH0gas	-89.7 kJ/mol
ΔfH0liquid	-120.9 kJ/mol
ΔfH0solid	? kJ/mol
S0gas, 1 bar	? J/mol·K
S0liquid, 1 bar	? J/mol·K
S0solid	? J/mol·K
Safety
Ingestion	Causes nausea and vomiting, with possible dizziness or hallucination.
Inhalation	In high concentration, may cause dizziness, unconsciousness, coma, and possible heart failure.
Skin	Mild irritant.
Eyes	Strongly irritating, producing tearing and burning sensations.
More info	Hazardous Chemical Database
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

Chloroform (also known as trichloromethane and methyl trichloride) is a chemical compound with formula CHCl₃. It is a colorless liquid with a pleasant, nonirritating odor and a slightly sweet taste. It does not support combustion in air, although above 290°C it will oxidize without flame.

History

Chloroform was first produced independently and simultaneously in 1831 by Justus von Liebig and the French chemist Eugene Souberain. Souberain's found that chloroform was produced by the action of bleach upon acetone or ethanol.

In 1847, the Edinburg obstetrician James Young Simpson first used chloroform to effect general anesthesia during childbirth. The use of chloroform during surgery expanded rapidly thereafter, especially in Europe. In the United States, chloroform did not replace ether as an anesthetic until the beginning of the 20th century.

Production

Industrially, chloroform is produced via two routes. In the more widely used method, methanol is treated with anhydrous hydrogen chloride, either by passing hydrogen chloride gas through boiling methanol or by passing combined methanol and hydrogen chloride vapors over an alumina catalyst at 350°C. In either case, the resulting chemical reaction produces chloromethane and water:

CH₃OH + HCl → CH₃Cl + H₂O

The chloromethane is then dried and reacted with chlorine gas at 400°C to produce chloroform according to the chemical equation

CH₃Cl + 2 Cl₂ → CHCl₃ + 2 HCl

This process also produces other chlorocarbons, especially methylene chloride (CH₂Cl₂) and carbon tetrachloride (CCl₄). The output gases of the reaction pass through a series of four distillation columns to sequentially isolate chloromethane, methylene chloride, chloroform, and carbon tetrachloride.

In the other major method of chloroform production, methane and chlorine are heated at 400°C to form the same mixture of products as the second step in the method already described. However, this method is becoming less common due to increased demand for chloromethane for producing silicone polymers.

Uses

In the early 1900's, chloroform was used as an inhaled anesthetic during surgery. However, safer, more flexible drugs have entirely replaced it in this role. The major use of chloroform today is in the production of the freon refrigerant R-22. However, this use can be expected to decline as R-22 is replaced by refrigerants that are believed to be less likely to cause ozone depletion.

Smaller amounts of chloroform are used as a solvent in the pharmaceutical industry, and for producing dyes and pesticides.

Safety

As might be expected from its use as an anaesthetic, chloroform depresses the central nervous system. Breathing about 900 parts of chloroform per million parts air (900 ppm) for a short time can cause dizziness, fatigue, and headache. Chronic chloroform exposure may cause liver and kidney damage, and some people develop sores when the skin is immersed in chloroform. Approximately 10% of the population has an allergic reaction to chloroform that produces a fever of around 40°C (104°F) upon exposure.

Animal studies have shown that miscarriages occur in rats and mice that have breathed air containing 30 to 300 ppm chloroform during pregnancy and also in rats that have ingested chloroform during pregnancy. Offspring of rats and mice that breathed chloroform during pregnancy have a higher incidence of birth defects, and abnormal sperm have been found in mice that breathed air containing 400 ppm chloroform for a few days. The effect of chloroform on reproduction in humans is unknown.

Chloroform once appeared in toothpastes, cough syrups, ointments, and other pharmaceuticals, but it has been banned in consumer products in the United States since 1976.