Anaesthesia => Ether
Ether (chemistry), more specifically ethyl ether or diethyl ether, colourless, liquid compound, (C2H5)2O, that boils at 34.6° C (94.3° F). Extremely volatile and flammable, with a powerful, characteristic odour and a burning, sweetish taste, ether is only slightly soluble in water (about 6 per cent), but mixes in all proportions with most organic liquids, such as alcohol and carbon disulphide. Ether itself is one of the most important organic solvents and is widely used in the laboratory as a solvent for fats, oils, resins, and alkaloids. A mixture of ether vapour with air is violently explosive; moreover, on long standing, ether may be partly oxidized to an explosive peroxide compound. Ether must therefore be stored and used with great care. Its principal uses are as a solvent, as a starting material for manufacture of chemical products, and as an anaesthetic.
Discovered probably as far back as the 13th century, ether is still prepared by one of the oldest known organic reactions, that is, the heating of ethyl alcohol with strong sulphuric acid. The temperature is carefully controlled so as to be between 130° and 150° C (266° and 302° F), because at higher temperatures the ether reacts further, yielding ethylene gas. The crude ether is purified by shaking with limewater (to remove acidic contaminants) and then with anhydrous calcium chloride (to remove unreacted alcohol and most of the water), and redistilling. Although containing small amounts of water, this ether is suitable for most purposes, including surgical use. If subsequent redistillation is made in the presence of phosphorous pentoxide or metallic sodium, the final product, absolute ether, is free of water and alcohol.