Estimating alcohol by total weight during fermentation? - Page 2 - Home Brew Forums

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09-01-2011, 02:14 PM   #11
ajdelange
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Ah, so you meant to invoke conservation of mass rather than the second law. Yes, conservation of mass holds: 2.0665 grams of extract is converted to 1 gram of alcohol, 0.9565 grams of CO2 and 0.11 grams of yeast. This doesn't account for lost water (or alcohol) vapor or O2 dissolved in the wort nor for esters, higher alcohols, VDK's....

09-01-2011, 07:44 PM   #12
Tubba
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Actually I meant to invoke the first law of thermodynamics (which is essentially conservation of mass in a relativistic context)

Anyway, the point is, no mass is added by the yeast cells, it is simply the case that not 100% of the disappeared extract turns into alcohol.

(Also, your CO2 figure looks absurdly precise. Is it as accurate as it is precise, or is it just extrapolated from 1 gram of alcohol?)

09-01-2011, 09:28 PM   #13
ajdelange
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Quote:
 Originally Posted by Tubba Actually I meant to invoke the first law of thermodynamics (which is essentially conservation of mass in a relativistic context)
OK but I don't notice much conversion of mass to energy even in my strongest brews (or the converse).

Quote:
 Originally Posted by Tubba Anyway, the point is, no mass is added by the yeast cells, it is simply the case that not 100% of the disappeared extract turns into alcohol.
Roger that.

Quote:
 Originally Posted by Tubba (Also, your CO2 figure looks absurdly precise. Is it as accurate as it is precise, or is it just extrapolated from 1 gram of alcohol?)
'Tisn't my figure. It's Balling's. How he got it I have no idea but I rather doubt that 5 significant digits is justified especially since the yeast value is given to two and is known to be quite variable. Nonetheless, if you convert extract loss to alcohol or alcohol to extract loss you are using his numbers.

09-02-2011, 01:10 PM   #14
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Quote:
 Originally Posted by ajdelange OK but I don't notice much conversion of mass to energy even in my strongest brews (or the converse).
There is, actually, to be fair. There are not nuclear reactions, for sure. However, the sugar molecules weigh more than the resulting alcohol/oxygen/CO2, the rest of the weight (just about infinitesimal) being either conversed to heat, or used in other chemical bindings between say, proteins in the yeast.

Quote:
 'Tisn't my figure. It's Balling's. How he got it I have no idea but I rather doubt that 5 significant digits is justified especially since the yeast value is given to two and is known to be quite variable. Nonetheless, if you convert extract loss to alcohol or alcohol to extract loss you are using his numbers.
Vaguely reminds me of those hand thermometers they have at hospitals, measuring the body temperature by IR light towards the eardrum. They'll give the temp as 37.1, 37.3, despite the fact that they are nowhere near that accurate.

09-02-2011, 01:28 PM   #15
passedpawn
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Quote:
 Originally Posted by Tubba Vaguely reminds me of those hand thermometers they have at hospitals, measuring the body temperature by IR light towards the eardrum. They'll give the temp as 37.1, 37.3, despite the fact that they are nowhere near that accurate.
Perhaps not accurate, but precise
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09-02-2011, 04:04 PM   #16
ajdelange
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Quote:
 Originally Posted by Tubba There is, actually, to be fair. There are not nuclear reactions, for sure. However, the sugar molecules weigh more than the resulting alcohol/oxygen/CO2, the rest of the weight (just about infinitesimal) being either conversed to heat, or used in other chemical bindings between say, proteins in the yeast.
The heat comes from bond energy which derives from a combination of coulombic and Van der Waals forces. There is no conversion of mass to energy in these reactions. What would convert? Certainly not protons or neutrons or the the subatomic particles that bind them together as the nuclei stay intact. The electron configurations do change and take up energy in the form of photons (photosynthesis) and release it as heat (fermentation) but photons have no mass so no mass is anihilated there.

If there is indeed mass loss it appears it would take a Feynman diagram, bra's or ket's to explain it and that's way over my head and I suspect yours.

09-03-2011, 07:53 AM   #17
Tubba
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Quote:
 Originally Posted by ajdelange The heat comes from bond energy which derives from a combination of coulombic and Van der Waals forces. There is no conversion of mass to energy in these reactions. What would convert? Certainly not protons or neutrons or the the subatomic particles that bind them together as the nuclei stay intact. The electron configurations do change and take up energy in the form of photons (photosynthesis) and release it as heat (fermentation) but photons have no mass so no mass is anihilated there. If there is indeed mass loss it appears it would take a Feynman diagram, bra's or ket's to explain it and that's way over my head and I suspect yours.
Gravity acts on all forms of energy, this includes bonding energy.

09-03-2011, 11:53 AM   #18
ajdelange
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Gravity is one of the 4 forces of nature the others being electromagnetic (which we covered when we mentioned coulombic and Van der Waals forces and photons), strong and weak. Anticipating that your next post will mention one or the other of these latter 2 as there seems to be no limit as to how silly you are willing to get, I will mention that they aren't relevant to this discussion either.

Nor is gravity. The atoms in a molecule do have mass, off course, and so, when in proximity, are subject to mutual gravitational attraction. But it is so small, relative to the other forces, as to be completely insignificant. For example, the hydrogen bond between two water molecules has an energy of about 18 kJ/mol. The work required to overcome the gravitational force between two water molecules separated by the length of a hydrogen bond and to move them infinitely far apart is about 3E-21 kJ/mol - that's almost 22 orders of magnitude!

09-03-2011, 12:03 PM   #19
Tubba
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I never said the amount was significant, only that you were wrong.

09-03-2011, 12:21 PM   #20
ajdelange
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Where exactly was I wrong?