volatile

a. [ F. volatil, L. volatilis, fr. volare to fly, perhaps akin to velox swift, E. velocity. Cf. Volley. ] 1. Passing through the air on wings, or by the buoyant force of the atmosphere; flying; having the power to fly. [ Obs. ] [ 1913 Webster ]

2. Capable of wasting away, or of easily passing into the aeriform state; subject to evaporation. [ 1913 Webster ]

☞ Substances which affect the smell with pungent or fragrant odors, as musk, hartshorn, and essential oils, are called volatile substances, because they waste away on exposure to the atmosphere. Alcohol and ether are called volatile liquids for a similar reason, and because they easily pass into the state of vapor on the application of heat. On the contrary, gold is a fixed substance, because it does not suffer waste, even when exposed to the heat of a furnace; and oils are called fixed when they do not evaporate on simple exposure to the atmosphere. [ 1913 Webster ]

3. Fig.: Light-hearted; easily affected by circumstances; airy; lively; hence, changeable; fickle; as, a volatile temper. [ 1913 Webster ]

You are as giddy and volatile as ever. Swift. [ 1913 Webster ]

Volatile alkali. (Old Chem.) See under Alkali. --
Volatile liniment, a liniment composed of sweet oil and ammonia, so called from the readiness with which the latter evaporates. --
Volatile oils. (Chem.) See Essential oils, under Essential. [ 1913 Webster ]