Emily Dickinson Lexicon

VOL'A-TILE-NESS, or VOL-A-TIL'I-TY, n. [Fr. volatilité.]

1. Disposition to exhale or evaporate; the quality of being capable of evaporation; that property of a substance which disposes it to rise and float in the air, and thus to be dissipated; as, the volatility of fluids. Ether is remarkable for its volatility. Many or most solid bodies are susceptible of volatility by the action of intense heat. By the spirit of a plant we understand that pure elaborated oil, which, by reason of its extreme volatility, exhales spontaneously, and in which the odor or smell consists . – Arbuthnot.
2. Great sprightliness; levity; liveliness; whence, mutability of mind; fickleness; as, the volatility of youth.