From ACE to ACENO: How America's Munson added Harley's British mixture to nitrous oxide

•George Harley pioneered alcohol–chloroform–ether (ACE) mixture for anesthesia (1860).•Corydon Munson adapted his 1886 gasometer by 1888 to vaporize ACE into nitrous oxide.•From Toledo, Ohio, Munson branded his gasometer as Excelsior and his gas as ACENO. An Ohio dentist, Corydon Munson, patented a gasometer with an attachment for vaporizing trace amounts of volatile general anesthetics or their mixtures into unoxygenated nitrous oxide. After vaporizing a variant of George Harley's ACE mixture into nitrous oxide, Munson branded his own novel anesthetic combination as ACENO.