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Old 07-09-2010, 02:14 PM   #1
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Default How much pure alcohol will 100g of white sugar produce ?

If I were to put 100g of pure white sugar into 1 lt of water, with some alcohol-resistant yeast (eg Champagne yeast), how many mililitres of pure alcohol would be produced when all of the sugar had been converted ?

Is there a table somewhere which displays this ?

Thanks.

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Old 07-09-2010, 02:18 PM   #2
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None.

To become pure alcohol you would have to distill out the water. Otherwise, you'd just have watery ethanol.

There are softwares, even free ones, that will calculate the percentage alcohol given the fermentables you choose.

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Old 07-09-2010, 04:59 PM   #3
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100g sucrose in 1000mL of water yields a solution with an original specific gravity of 1.039. Assuming you do something about the lack of free amino nitrogen during fermentation, an apparent attenuation of 75% - 80% is reasonable. That should yield a finishing specific gravity of 1.007 - 1.009. From there, the math is easy.

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Old 07-09-2010, 06:10 PM   #4
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Quote:
Originally Posted by Yuri_Rage View Post
an apparent attenuation of 75% - 80% is reasonable.
Huh? Sucrose is going to be far more fermentable than that, isn't it? i would expect an apparent attenuation of well over 100%.
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Old 07-09-2010, 06:14 PM   #5
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One, how would you get an attenuation of OVER 100% and two, it's yeast dependent on attenuation. Like Gila said, you need to distill to get pure alcohol, and we don't do that here.

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Old 07-09-2010, 06:31 PM   #6
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Quote:
Originally Posted by Scimmia View Post
Huh? Sucrose is going to be far more fermentable than that, isn't it? i would expect an apparent attenuation of well over 100%.
+1, I've done pure sucrose fermentations and got FGs substantially below 1.000. IrregularPulse: that's *apparent* attenuation. 100% attenuation is about 122% apparent attenuation. A 1.040 solution would ferment down to about 0.991.

To answer the question as directly as possible, 100 g of sucrose is 0.292 mol, and stoichiometrically 1 mol sucrose yields 4 mol EtOH, so you'd expect to get 54.0 g, which is about 68.3 mL.
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Old 07-09-2010, 08:03 PM   #7
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Quote:
Originally Posted by IrregularPulse View Post
One, how would you get an attenuation of OVER 100% and two, it's yeast dependent on attenuation. Like Gila said, you need to distill to get pure alcohol, and we don't do that here.
One, as a10t2 already pointed out, there's a big difference between apparent attenuation and real attenuation. Don't forget that ethanol has a lower specific gravity than water.

Two, it is dependent on the yeast to a small extent, but the apparent attenuation numbers the labs give are based on an average wort. A sucrose solution is going to be far, far more fermentable without all of the long chain sugars.
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Old 07-10-2010, 02:48 AM   #8
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Old 07-10-2010, 05:04 AM   #9
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Old 07-10-2010, 12:10 PM   #10
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Thanks.

After posting I found a recipe for fermented spirit.

It said that 8kg of sugar added to 21 lt of water would produce 25lt of 20% spirit.

So that's 5lt of pure alcohol.

1.6kg of sugar would make 1lt, and so 100g would make 62.5 ml.

(Yes, realise that distillation would be required, but I was asking about how much pure ethanol would be suspended in the solution once 100% of the sugar had been converted.)

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