Page:The American Cyclopædia (1879) Volume VI.djvu/759

 ETHER 747 portions of the atmospheres of worlds in the in- terstellar spaces ; and the retardation of comets has been ascribed to this matter. This argu- ment is not affected by the law that light de- creases in proportion to the square of the dis- tance, because, although the rays diverge in all directions from every source, the field of the heavens, as Prof. Grove remarks, is everywhere studded with suns, so that the sum of the rays which would reach the earth, if they retained their luminous property, would furnish more light than is actually received. Again, when as near an approach to a vacuum as is possible has been formed, it has been found to offer an effectual barrier to the passage of the electric spark; and regarding electricity as a correla- tion of light and heat, it is asked why it will not employ the ethereal medium which upon that hypothesis must pervade the vacuum. This objection loses weight from the fact that the space which contains no medium for the transmission of electricity, nevertheless offers one for the transmission of light and heat. The difficulty of accounting for the polariza- tion of light by assuming that the undulations take place in the molecules of the polarizing body, is greatly diminished by adopting the doctrine of a special medium, as the luminif- erous ether. A further consideration of the subject will be found in the articles LIGHT and HEAT. (See also ELASTICITY.) ETHER) in chemistry, the name given to a class of highly volatile, inflammable, spirituous liquids, possessing a sweetish taste and pecu- liar fragrance, obtained commonly by distilling alcohol in mixture with some acid. Their composition is somewhat variable according to the acid employed in their preparation, and this gives them their distinctive names, as sul- huric ether, nitric ether, &c. Yet these ds do not in all cases furnish any of the in- ients of the ether, and the same ether may etimes be produced by the action of other bstances upon alcohol, as well as of the' acid Hy employed. This is especially the case ith sulphuric ether, and as it contains no sul- uric acid, and is by far the most common of ether, it is now admitted into the hited States and London pharmacopoeias by name of aether, as it was before known in imon use. This ether, it is supposed, was own to Raymond Lully, who lived in the 3th century. Valerius Cordus in 1540 de- ribed the method of making it. Frobenius in 1730 first brought it prominently forward in a paper published in the "Philosophical Transactions;" and by a note appended to this, it appears that Boyle and Newton had both directed their attention to it. The prepa- ration of ether was formerly conducted by dis- tilling in a glass retort a mixture of equal parts of sulphuric acid and alcohol at a moderate heat, and, when about one third of the whole had come over, adding half as much alcohol as before, and again distilling. But a better method is to conduct the process on a larger scale with the use of a leaden still heated by high steam passed through in a spiral pipe; and the alcohol is best introduced in small quantities at a time by a pipe which passes through the upper part of the still. Such is the apparatus used at the apothecaries' hall, London. The heating by steam obviates the danger of explosion, to which the process is liable when the vapors that escape come in contact with a flame. The apparatus given by Brande is convenient either on a large or small scale. ^ In a glass flask are introduced 8 parts by weight of concentrated sulphuric acid and 5 parts of spirit of wine of specific gravity 0-834. This is set in a small sand bath, which may be conveniently heated by a gas light. A thermometer graduated at least to 320 F. passes through the cork, the bulb being in the liquid. There is also a tube reaching to the bottom, and expanding at top into a funnel. This is intended to receive more alcohol slow- ly dropped into it as the process goes on. A glass tube of large bore conveys the vapor through the condenser, which is surrounded with cold water, and the liquid drops from the end of the tube into a proper receiver. By keeping the temperature as nearly as possible to 300, the ebullition goes on rapidly, and the quantity of liquid in the flask may be kept nearly the same for several hours, the alcohol as fast as it is admitted being converted into the vapor of ether and of water. These con- dense together, but in the receiving vessel they separate, the water sinking to the bottom to- gether with T V of its volume of ether dissolved in it. If a weak acid be used or too much al- cohol, so that the boiling point of the mixture is reduced below 260, the alcohol is apt to pass over unchanged. It is important to keep up a rapid, or even violent boiling, at a tem- perature between 260 and 310. At about 320 olefiant gas and other undesirable pro- ducts are generated. By the continuous pro- cess of Dr. Brande, a small quantity of sulphu- ric acid may be made to convert into ether a large quantity of alcohol. It might serve for an indefinite time but for its slow volatilization and the passing over of its vapor with the others. Ether is purified by shaking it in a close vessel with twice its bulk of water. After standing, the ether is poured off, and the water that may be still present is taken up by mixing quicklime with it. Then by distil- ling, pure ether is obtained. Ether is remark- able for its great volatility. Its vapor escapes in pouring the fluid from one vessel into another, so that if a lighted candle is near there is danger of the whole being suddenly inflamed. A mixture of 10 volumes of oxygen and one of ether vapor explodes violently by an electric spark. The vapor is so much more dense than air, being as 2 -58 to 1, that it can be poured out of one vessel into another, dis- placing the air in this, and showing^ its pres- ence by taking fire on the application of a match. Its rapid evaporation produces in-