QUALITIES. A colourless liquid of specific gravity 739°. _Odour_, pungent and fragrant; it is highly volatile, and when perfectly free from alcohol it boils at 98°; it is extremely inflammable, a circumstance which should be remembered when it is poured from one vessel to another by candle light. CHEMICAL COMPOSITION. When pure it consists of oxygen, hydrogen, and carbon; the rectified æther however still contains some water and alcohol, for Lovitz obtained an æther of 632. SOLUBILITY. One part requires for its solution ten of water; with alcohol and ammonia it unites in every proportion. SOLVENT POWERS. It is one of the most powerful solvents known in vegetable chemistry, as it dissolves balsams, resins, gum-resins, wax, camphor, extractive, &c.; it takes up about a twentieth of its weight of sulphur, but it exerts no solvent power upon the fixed alkalies. FORMS OF EXHIBITION. In any liquid vehicle, if in decoctions or infusions, they should be previously cooled. _See Formulæ 20, 22, 23_. MEDICAL USES. It is highly valuable as a diffusible stimulant, narcotic, and antispasmodic. DOSE, fʒss to fʒij, which, in order to produce the full effect of the remedy, must be repeated at short intervals. Æther, independent of such virtues, has another valuable property consequent upon its rapid evaporation, that of producing cold and dryness; it is therefore, when externally applied and allowed to evaporate, a most powerful refrigerant, and has proved valuable in scalds or burns, in facilitating the reduction of strangulated hernia, and in diminishing excessive circulation in the brain; if however it be so confined, that its rapid evaporation is prevented, a very opposite effect is produced, and it proves stimulant, rubefacient, and even vesicatory. With regard to the other property incidental to it, that of producing dryness, I am not aware that it has hitherto been applied to any pharmaceutical purpose; the fact may be satisfactorily shewn by a very simple experiment,—by rincing a phial with æther, to the interior of which drops of water obstinately adhere, when by exposing it to a current of air, it will be completely dry in a few minutes. It may be noticed in this place that a mixture of sulphuric and muriatic æthers evaporates instantaneously, and produces a degree of cold considerably below 0 of Fahrenheit. OFFICINAL PREPARATIONS. _Spiritus Æther: Sulph:_ L. _Spir: Æth: Sulph: comp:_ L. _Spir: Æth: Aromat:_ L. ADULTERATIONS and IMPURITIES. Its specific gravity affords the best indication of its purity; _Sulphuric Acid_ may be detected by a precipitation on the addition of a solution of baryta, and by its reddening the colour of litmus; _Alcohol_, by its forming with phosphorus a milky instead of a limpid solution. M. Gay Lussac has observed that when kept for a considerable time without disturbance, it undergoes spontaneous decomposition, and that acetic acid, perhaps some alcohol, and a particular oil, are produced from it.