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 sodium ethylate on ethyl iodide, and showed that all ethers must possess the structural formula given above (see also Brit. Assoc. Reports, 1850, 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 mariner 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. Péligot (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 140° 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 23.6º 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·HCl (C. Friedel, Comptes rendus, 1875, 81, p. 152). Methyl ethyl ether, CH3·O·C2H5, 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 10.8º C.
For diethyl ether see [Ether], and for methyl phenyl ether (anisole) and ethyl phenyl ether (phenetole) see [Carbolic Acid].
ETHICS, the name generally given to the science of moral philosophy. The word “ethics” is derived from the Gr. ἠθικός, that which pertains to ἦθος, character.
For convenience in reference, the arrangement followed in this article may be explained at the outset:—
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| I. | DEFINITION AND SCOPE | [809] |
| II. | HISTORICAL SKETCH | [810] |
| A. Greek and Graeco-Roman Ethics | [810] | |
| The Age of the Sophists | [811] | |
| Socrates and his Disciples | [811] | |
| Plato | [812] | |
| Plato and Aristotle | [814] | |
| Aristotle | [815] | |
| Stoicism | [816] | |
| Hedonism (Epicurus) | [818] | |
| Later Greek and Roman Ethics | [818] | |
| Neoplatonism | [819] | |
| B. Christianity and Medieval Ethics | [820] | |
| Christian and Jewish “Law of God” | [820] | |
| Christian and Pagan Inwardness | [820] | |
| (Knowledge, Faith, Love, Purity) | ||
| Distinctive Particulars of Christian Morality | [821] | |
| Development of Opinion in Early Christianity, Augustine, Ambrose | [823] | |
| Medieval Morality and Moral Philosophy | [824] | |
| Thomas Aquinas | [824] | |
| Casuistry and Jesuitry | [826] | |
| The Reformation; and birth of Modern Thought | [826] | |
| C. Modern Ethics | [827] | |
| Grotius | [827] | |
| Hobbes | [827] | |
| The Cambridge Moralists | [828] | |
| (Cudworth, More) | ||
| Cumberland | [829] | |
| Locke | [829] | |
| Clarke | [829] | |
| Shaftesbury | [830] | |
| Mandeville | [830] | |
| Butler | [831] | |
| Wollaston | [831] | |
| Hutcheson | [831] | |
| Hume | [832] | |
| Adam Smith | [833] | |
| The Intuitional School | [833] | |
| (Price, Reid, Stewart, Whewell) | ||
| The Utilitarian School | [835] | |
| (Paley, Bentham, Mill) | ||
| Association and Evolution | [837] | |
| Free-will | [837] | |
| French Influence on English Ethics | [838] | |
| (Helvetius, Comte) | ||
| German Influence on English Ethics | [839] | |
| (Kant, Hegel) | ||
| D. Ethics since 1879 | [840] | |
| III. | Bibliography | [845] |
Section I. contains a general survey of the subject; it shows in what sense ethics is to be regarded as a special field of philosophical investigation—its relations to other departments of thought, especially to psychology, religion and modern physical science. The article makes no attempt to give a detailed, casuistical examination of the matter of ethical theory. For this, reference must be made to special articles on philosophic schools, writers and terms.
Section II. is a historical sketch in four parts tracing the main lines of development in ethical speculation from its birth to the present day. Here again it has been possible to notice only the salient points or landmarks, leaving all detail to special articles as above. All important writers whose names occur in this sketch are treated in special biographical articles, and references are given as often as possible to supplementary articles which illustrate and explain points which cannot be fully treated here. This is especially the case in connexion with technical terms (whose history and meaning are inevitably taken for granted) and biographical information about minor ethical writers.