Anaesthesia => Chloroform
Trichloromethane, CHCl3. A colourless liquid, half again as dense as water and of about the same viscosity, trichloromethane has a heavy, ether-like odour and a burning sweetness of taste, being about 40 times as sweet as cane sugar. It is almost insoluble in water, but it is freely miscible with organic solvents and is an important solvent for gums, resins, fats, elements such as sulphur and iodine, and a wide variety of organic compounds.
Trichloromethane may be prepared by the chlorination of ethyl alcohol or of methane, or by the action of iron and acid on carbon tetrachloride; the latter is the principal industrial method in current use.
Trichloromethane was first prepared in 1831 and was first used as an anaesthetic in 1847 in one of the earliest experiments on surgical anaesthesia. In the presence of light, however, it tends to decompose, yielding the highly poisonous compound carbonyl chloride (phosgene). Even when pure, it causes fatal cardiac paralysis in about one out of 3,000 cases, and so is seldom used for anaesthesia.