What is fusel oil?

   Fusel oil (alcohol oil, potato oil) is a colorless, oily mixture of liquids composed mainly of amyl alcohols, with some butyl, propyl, and allyl alcohols. Fusel oil is formed during the fermentation of grain, potatoes, and beetroot. When such fermented liquors are fractionally distilled, the ethyl alcohol forms and distills over first. The fraction which distills from 105 °C. to 137 °C. is called "fusel oil." Fusel oil is always present not only in the crude spirits but to a small degree in rectified alcohol and spirits. Its specific gravity is about 0.83. The liquid has a characteristic odor and is practically insoluble in water. When present in alcoholic liquors it imparts a nauseous odor and taste. Significant amounts of fusel oil are poisonous. During the aging of liquors the fusel oil is converted to esters. Fusel oil is used in the preparation of solvents for resins and lacquers. The amyl alcohols are used in the preparation of "fruit essences," which are used for flavoring purposes. Fusel oil is also employed as a solvent for fats and alkaloids.