Comment on Why is alcohol measured in percentages?
bouh@lemmy.world 6 months ago
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?
subtext@lemmy.world 6 months ago
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] - en.wikipedia.org/wiki/Ethanol [2] - en.wikipedia.org/wiki/Alcohol_proof
excitingburp@lemmy.world 6 months ago
It does: en.wikipedia.org/wiki/Vapor_pressure. In an airtight container you would have an equilibrium of alcohol vapor and liquid. In open-atmosphere, the atmosphere basically behaves like an infinitely large volume for the vapor - so the alcohol will completely vaporize (and cool the surface it is on in order to do so).
It’s also trivial to demonstrate by pouring alcohol onto a surface, it disappears in seconds. Same with gasoline and numerous other liquids you’ve surely seen do this (another example is hand sanitizer, which is basically pure alcohol).
Being diluted doesn’t really help with any of this though. Also alcohol is kept in bottles, which are usually airtight until they are first opened.
subtext@lemmy.world 6 months ago
I mean sure, but you could say that about any liquid, or even any solid for that matter (with sublimation). But that’s not really what I was talking about when I responded.
excitingburp@lemmy.world 6 months ago
It was what the GP was, though.