Boiling Points of Ethanol, Methanol, and Isopropyl Alcohol

Boiling Points of Ethanol, Methanol, and Isopropyl Alcohol

Distillation of alcohol
Alcohol has a much lower boiling point than water. One practical application of this is distillation. Lebazele / Getty Images

The boiling point of alcohol depends on which type of alcohol it is as well as the atmospheric pressure. Keep in mind, the boiling point decreases as atmospheric pressure decreases, so it will be slightly lower unless you are at sea level. Here is a look at the boiling point of different types of alcohol.

The boiling point of ethanol or grain alcohol (C2H5OH) at atmospheric pressure (14.7 psia, 1 bar absolute) is 173.1°F (78.37°C).

Methanol (methyl alcohol, wood alcohol): 66°C or 151°F

Isopropyl Alcohol (isopropanol): 80.3°C or 177°F

Implications of Different Boiling Points

One practical application of the different boiling points of alcohols and of alcohol with respect to water and other liquids is that it can be used to separate them using distillation. In the process of distillation, a liquid is carefully heated so more volatile compounds boil away. They may be collected, as a method of distilling alcohol, or the method may be used to purify the original liquid by removing compounds with a lower boiling point. Different types of alcohol have different boiling points, so this can be used to separate them from each other and from other organic compounds. Distillation may also be used to separate alcohol and water. The boiling point of water is 212°F or 100°C, which is higher than that of alcohol. However, distillation can't be used to fully separate the two chemicals.

The Myth About Cooking Alcohol out of Food

Many people believe alcohol added during the cooking process boils away, adding flavor without retaining alcohol. While it makes sense cooking food above 173°F or 78°C would drive off the alcohol and leave the water, scientists at the University of Idaho Department of Agriculture have measured the amount of alcohol remaining in foods and found most cooking methods don't actually affect the alcohol content as much as you might think.

  • The highest amount of alcohol remains when alcohol is added to boiling liquid and then removed from heat. About 85% of the alcohol remained.
  • Flaming the liquid to burn off the alcohol still allowed for 75% retention.
  • Storing food containing alcohol overnight with no heat applied resulted in 70% retention. Here, the loss of alcohol occurred because it has a higher vapor pressure than water, so some of it evaporated.
  • Baking a recipe containing alcohol resulted in alcohol retention ranging from 25% (1 hour baking time) to 45% (25 minutes, no stirring). A recipe had to be baked 2 hours or longer to bring the alcohol content down to 10% or lower.

Why can't you cook the alcohol out of food? The reason is because alcohol and water bind to each other, forming an azeotrope. The components of the mixture can't be easily separated using heat. This is also why distillation isn't sufficient to get 100% or absolute alcohol. The only way to completely remove alcohol from a liquid is to boil it away completely or allow it to evaporate until it's dry.