section_path: Alcohol measurement/Alcohol concentration
section_name: Alcohol concentration
paragraph_text: Alcohol concentration
  
  The concentration of alcohol in a beverage is usually stated as the percentage of alcohol by volume (ABV, the number of milliliters (ml) of pure ethanol in 100 ml of beverage) or as proof. In the United States, proof is twice the percentage of alcohol by volume at 60 degrees Fahrenheit (e.g. 80 proof = 40% ABV). Degrees proof were formerly used in the United Kingdom, where 100 degrees proof was equivalent to 57.1% ABV. Historically, this was the most dilute spirit that would sustain the combustion of gunpowder.
  
  Ordinary distillation cannot produce alcohol of more than 95.6% by weight, which is about 97.2% ABV (194.4 proof) because at that point alcohol is an azeotrope with water. A spirit which contains a very high level of alcohol and does not contain any added flavoring is commonly called a neutral spirit. Generally, any distilled alcoholic beverage of 170 US proof or higher is considered to be a neutral spirit.
  
  Most yeasts cannot reproduce when the concentration of alcohol is higher than about 18%, so that is the practical limit for the strength of fermented drinks such as wine, beer, and sake. However, some strains of yeast have been developed that can reproduce in solutions of up to 25% ABV.