ETHERS  , in organic

chemistry, compounds of the general formula R•O•R', where R, R'=alkyl or aryl groups . They may be regarded as the anhydrides of the alcohols, being formed by elimination of one molecule of water from two molecules of the alcohols; those in which the two hydrocarbon radicals are similar are known as simple ethers, and those in which they are dissimilar as mixed ethers . They may be prepared by the action of concentrated sulphuric acid on the alcohols, alkyl sulphuric acids being first formed, which yield ethers on heating with alcohols . The process may be made a continuous one by running a thin stream of alcohol continually into the heated reaction mixture of alcohol and sulphuric acid . Benzene sulphonic acid has been used in place of sulphuric acid (F . Krafft, Ber., 1893, 26, p . 2829) . A . W . Williamson (Ann., 1851, 77, p . 38; 1852, 81, p . 77) prepared ether by the action of sodiumethylate on ethyl iodide, and showed that all ethers must possess the structural formula given above (see also Brit .

Assoc . Reports, 185o, p . 65) . They may also be prepared by heating the alkyl halides with

silver oxide . The ethers are neutral volatile liquids (the first member, methyl ether, is a gas at ordinary temperature) . Phosphorus pentachloride converts them into alkyl chlorides, a similar decomposition taking place when they are heated with the haloid acids . Nitric acid and chromic acid oxidize them in such a manner that they yield the same products as the alcohols from which they are derived . With chlorine they yield substitution products . Methyl ether, (CH3)2O, was first prepared by J . B . Dumas and E . Peligot (Ann. chim. phys., 1835, [2] 58, p .

19) by heating methyl alcohol with sulphuric acid . It is best prepared by heating methyl alcohol and sulphuric acid to 14o° C. and leading the evolved gas into sulphuric acid . The sulphuric acid

solution is then allowed to drop slowly into an equal volume of water, when the methyl ether is liberated (E . Erlenmeyer and A: Kriechbaumer, Ber., 1874, 7, p . 699) . It is a pleasant-smelling gas, which burns when ignited, and may be condensed to a liquid which boils at 23.6° C . It is somewhat soluble in water and readily soluble in alcohol, and concentrated sulphuric acid . It combines with hydrochloric acid gas to form a compound (CH3)2O•HC1 (C . Friedel, Comptes rendus, 1875, 81, p . 152) . Methyl ethyl ether, CH3.O•C,H5, is prepared from methyl iodide and sodium ethylate, or from ethyl iodide and sodium methylate (A . W .

Williamson, Ann., 1852, 81, p . 77) . It is a liquid which boils at ro•8° C . For diethyl ether see ETHER, and for methyl phenyl ether (anisole) and ethyl phenyl ether (phenetole) see CARBOLIC ACID .