The process of the U. S. Pharmacopoeia consists in first shaking un-purified ether and water strongly together, and, after subsidence, pouring off the supernatant ether, thus deprived of its alcohol; then agitating this with chloride of calcium and quicklime, in fine powder, so as to separate the water; and lastly, distilling off only a portion of the liquid. Even thus strengthened and purified, ether is not absolutely pure, as it still contains a little alcohol; but it is sufficiently pure for all medical uses. The British process is essentially the same.

Properties

Ether is a colourless liquid, having, when quite pure. the sp. gr. of about 0.712; but, as directed in our officinal code, it has in the crude state the sp. gr. 0.750, according to the British Pharmacopoeia 0.735; and in the pure state (aether fortior) 0.728, U.S., and 0.720, Br. In the latter condition, it should not lose more than from one-tenth to one-eighth by agitation with water; should boil actively when a test-tube half filled with it is held in the hand, and a small piece of glass is dropped into it; and, when half a fluidounce of it is moved backward and forward upon a porcelain plate, should yield a faint aromatic odour as the last portions are volatilized, and leave the surface of the plate without smell or taste, but covered with moisture. These are the officinal teste of its sufficient purity.

The odour of ether is strong, penetrating, and rather grateful; its taste, hot and pungent, yet somewhat cooling also. It is extremely volatile, rapidly escaping when exposed to the air, and producing cold during its vaporization. Its boiling point is extremely low, scarcely exceeding the heat of one of our hot summer days. It is also highly inflammable; and its vapour forms an explosive mixture with atmospheric air. Caution should, therefore, be observed not to allow the too near approach of flame when it is used. The affinity between it and water is not strong. Nine parts by measure of water will dissolve one part of ether; and, conversely, ether will take up about the same proportion of water. If mixed in other proportions, the two liquids will separate, the ether floating on the surface. It unites in all proportions with alcohol. On exposure to the air, it undergoes gradual decomposition, producing acetic acid and water. It should evaporate wholly on exposure, and should not become milky on being mixed with water.

Composition

All agree that ether consists of 4 eqs. of carbon, 5 of hydrogen, and 1 of oxygen (C4H5O); but, as to the precise mode in which its constituents are combined, different views have been entertained. According to the one most generally received, it is simply the oxide of ethyl, consisting of 1 eq. of ethyl (C4H5) and 1 of oxygen.