In an ethanol plants, the mixture of water and ethanol from the beer column distillate contains about 40% ethanol (molar basis) in water,together with the fusel oils described in the previous problem.This mixture is distilled to give an azeotropic mixture of ethanol and water(89% ethanol) overhead, with 99.9% recovery of ethanol.The fusel oil can cause blending problems if it is allowed to accumulate in the distillate.Fusel oil is a mixture of higher alcohols and ethers that can be approximated as a mixture of n-butanol and diethyl ether.