>> wish to calculate the alcohol content.
> I think you need to have a measurement prior to fermentation

Actually there is another way by weighing a known volume, then evaporating
off the alcohol and weighing what's left.  Comparing before and after
weights will give you the alcohol percentage, but I don't recall the
specifics.  This thread is will probably be more fruitful on the mead lovers
list.

Aaron Morris - thinking better living through chemistry!