"Aaron Puhala" > wrote in message >...
> Ray's assertion is correct.

I don't agree.

>While simple conversions tend to work very well
> over time for established operations,
> Potential Alcohol calculation is by no means straightforward in the larger
> sense.

Agreed.

> The conversion factor of 0.55 to calculate
> Potential Alcohol from Brix is a pretty standard industry value and has
> worked well for me in general. Strictly speaking, every
> gram of sugar consumed by the yeast will liberate at most 0.511 grams of
> ethanol.

Every gram of sugar converted to ethanol will result in .511 grams of
ethanol. More on this later.

This means that the 22.8 Brix could yeild a potential 11.65 w/w%
> Ethanol which is about 14.3 v/v%.

OK, I'll agree to this.

> To achieve this level of ethanol after
> fermentation would
> require absolutely complete extraction of all sugar, 100% yeast efficiency,
> 0% evaporative loss, and
> yeast fermentation to 0.00% residual sugar.

Don't forget the 5% of sugars that are used by the yeast but are not
converted to ethanol. My references say about 1% goes to new cells and
4% will end up as other compounds like pyruvate, acetate,
acetaldehyde, glycerol and lactate.

> Needless to say, this is highly
> unlikely so usefull "conversion factors"
> like the 0.55 discussed have become commonplace.

And because the hydrometer makers have to use one conversion factor.
They can not take these other variable into account because they vary
from fermentation to fermentation.

> I believe a range of
> conversion factors of 0.54 - 0.62
> would cover the vast majority of observed results in the industry globally
> resulting in a v/v% ethanol range of
> 12.3% to 14.1% depending on the vast array of variables that can affect
> conversion, efficiency, and loss.

I can't agree with the .62. Theoretically possible but not practically
possible. I think the .55 mark is more realistic in the home wine
making world and I believe it can be lower than that.

But back to Ray's comment, what ever the hydrometer uses as a
conversion rate (.55 is common because that is a common estimate and
probably pretty accurate for most circumstances) this assumes that the
wine has been fermented to dryness. That all of the sugars have been
consumed and the SG is somewhere in the .992-.994 range.

If the SG is still at the 1.000 range, either there is still some
sugar left or there was something other in solution besides sugar that
effected the original SG. Either way, you did not get as much alcohol
as anticipated, I would think around 1% ABV lower.

This is not to say that the hydrometer is a very accurate predictor of
alcohol, only that it's prediction is based on all sugars being
consumed and the final SG value being below 1.000.

Andy