Drinkipedia
Ebulliometer
A ebulliometer is a laboratory apparatus used to determine the alcohol content of dry wine. It measures the precise boiling point of the wine; then, taking into consideration the atmospheric pressure at the time, the analyst determines the alcohol content from the relative boiling points of pure alcohol, water and the wine. The boiling point of any wine is always somewhere in between that of pure alcohol and pure water since wine itself always contains both. (Wine,Beer,Spirits,Sake,Mead/Production)