"exhaling, without your consciousness, like ether out of a phial; so that, at every glance, you find a smaller and less volatile residuum"
Patient being anesthetized with ether in 1846 (1920s)
Public DomainPatient being anesthetized with ether in 1846 (1920s) - Credit: Ernest Bord

Ether, a liquid chemical formerly used as a general anesthetic, has a boiling point of just 94°F and for this reason evaporates very easily. 

Ether
Creative Commons Attribution Share AlikeEther - Credit: Brandon Martin-Anderson