This is useful in producing high quality alcoholic beverages, while ensuring that less desirable components (such as fusel alcohols) are returned to the primary flask.
These substances include small amounts of chemicals such as other alcohols (known as fusel alcohols), acetone, acetaldehyde, esters, tannins, and aldehydes (e.g. propanol, furfural, glycols, ethyl acetate).
It (along with similar fusel alcohols) is reputed to be responsible for severe hangovers, although experiments in animal models show no evidence for this.
