the meaning of "proof"

[gib65]

What's the meaning of "proof" when it comes to alcohol? I thought it meant percentage of alcohol but then read something that said 150 proof. So what does it mean?

[insane_alien]

its done in half percentages so 200 proof is 100% alcohol.

 

by the way this would be more apropriate in organic chemistry as alcohols are organic.

[jdurg]

Correct. So your 150 proof bottle is 75% alcohol. Just take whatever proof is listed and divide it by two to get your actual percentage R-OH.

[silkworm]

I think it comes from the tendency of drunk people to exagerrate. I don't think 2 is the appropriate scale though.

[insane_alien]

silk, 2 is the definite scale. see http://www.madsci.org/posts/archives/feb98/888729125.Ch.r.html

 

if its not 2 then i've got to get me the new edition of my chemistry books.

 

i think the scale came about because it allowed greater accuracy without fractions. and it was before decimilization so it wasn't based on a power of 10 scale.

[silkworm]

Insane, I didn't mean to imply that what you were saying the scale was wrong. I was making a joke that a drunk exagerrating something only twice as much is an underestimate. I'm taking AP's position of belittling people who drink, it makes me feel big.

 

Interesting link. I'd like to know for sure why the doubling was used. I see your point, but is it really necessary to express a half a percent for something your drinking? I mean, I can see needing to be precise enough to be within a couple of a percent, but a half? Who knows when proofs got to be accurate at all?

 

We need Robert Wuhl.

[jdurg]

It may have something to do with limitations of printing presses at the time, and by using non-fractional or non-decimal numbers the strength of an alcohol could be denoted.

[gib65]

Thanks everyone. Makes sense now