I feel like it would be useful to know exactly how much alcohol is in a can or a bottle. Also why is alcohol the only thing measured in percentages and not sugar or caffeine or medicine?
I feel like it would be useful to know exactly how much alcohol is in a can or a bottle. Also why is alcohol the only thing measured in percentages and not sugar or caffeine or medicine?
I think alcohol can’t be kept pure in normal conditions, it would turn into a gas. So it is diluted by necessity. Knowing the full volume of the thing is certainly better than knowing only the quantity of alcohol without knowing the degree of dilution.
It is not the only product to be indicated this way. All diluted chemicals are. I think syrup is also?
The boiling point of pure ethanol is 78°C / 173°F [1], so it would not turn into a gas at normal conditions.
Pure ethanol is very hard to produce because it forms an azeotrope with water in the ~96% [1] range, meaning it cannot be distilled further than that, it must be separated by other means.
Alcohol in spirits is usually diluted because of taxes on higher percentage alcohol, consumer preference, or being able to make more bottles with the same amount of ethanol. I believe using percentages for alcohol began when ye olde England was putting taxes based on the percentage of alcohol in the drink [2].
[1] - https://en.wikipedia.org/wiki/Ethanol [2] - https://en.wikipedia.org/wiki/Alcohol_proof