Measuring alcohol content

[beerguy2009]

OK, I know you can measure the OG and the FG to calculate alcohol content but is there a way to measure it on a finished beer? Is ther something other than a hydrometer that can do this? This is just a thought that has been going through my brain.

 

[northernlad]

If you don't have an OG and an FG you can only make a guess. Its like algebra. You need 2/3 variables.

 

[remilard]

OK, I know you can measure the OG and the FG to calculate alcohol content but is there a way to measure it on a finished beer? Is ther something other than a hydrometer that can do this? This is just a thought that has been going through my brain.

There are specialized instruments and it can also be done with a gas chromatograph.

I'm guessing you don't want to know that bad.

 

[ajf]

Yes, you need an ebulliometer.
Personally, I'm more interested in what it tastes like.

-a.

 

[beerguy2009]

Thanks for the answers. I was just courious if there was a way. Like ajf said taste is more important but I am a guy who wants to know more and that thought was in my brain so I asked here.
Thanks again for the responses.

 

[david_42]

Real simple. All you need is a decent scale. Weight out 100 gm of beer, heat in a water bath until the temperature hits 200F, re-weigh. This will boil off most (about 95%) of the alcohol.

 

[beerguy2009]

Real simple. All you need is a decent scale. Weight out 100 gm of beer, heat in a water bath until the temperature hits 200F, re-weigh. This will boil off most (about 95%) of the alcohol.

Interestng idea. Should it be covered while heating to retain the water (or would that retain the alcohol also)?

 

[terrencepickles]

Interestng idea. Should it be covered while heating to retain the water (or would that retain the alcohol also)?

Yes, cover it. Then punch a hole in your cover and connect a tube to it; collect drippings. You have just created a still, and whiskey.

 

[AiredAle]

If you know the OG, then a good estimate is to divide by ten, and you have alcohol by volume. For example, an pale ale with an original gravity of 54 will have about 5.4 % alcohol by volume. This assumes a normal 75% or so apparent conversion, with a finishing gravity about 12-14.

A good fractional distillation will give you the answer, but you need a distillation column that will give good separation of the alcohol from the water. Also, you will get all the alcohol but some of the water since alcohol and water form a 95% alcohol 5% water azeotrope, so you would have to add back 5% of the weight of collected alcohol/water mixture to get an accurate calculation.

I'd stick to the OG divided by ten, it's easier and now equipment and time is needed.