>
> Hi again,I had a look at the sulphite table,which is for potassium
> metabisulphite.My numbers were for sodium metabisulphite and for 50ppm
> correspond to 2.5g of sodium metabisulphite/5 gallons.In your table
> using the potassium salt,50 ppm corresponds to 1.64g of potassium
> metabisulphite.It seems to me that maybe you should need a higher mass
> of potassium salt to get the equivalent amount of sulphite to the
> light sodium salt,but maybe my chemistry is failing me.So you could be
> right and my numbers for sodium are too high.I will investigate
> further! Cheers,Michael

Michael:

The formsoft online sulfite table generator can be set tp either
sodium or potassium. You do need more potassium based powder than
sodium, that's correct. However, I do believe that 2.5g of either is
too high to give you 50 ppm of SO2 in your wine. Here's another link -
an in depth explanation of sulfites in wine - which should cover all
your questions in detail:

http://www.brsquared.org/wine/ under Articles -> Sulphur Dioxide

In section 19, there is a couple of sample calculations - they're for
potasium meta but you can adjust them for sodium meta by using the
67.4 factor instead of 57.6. I did the 2nd calculation for your
numbers and it gives the same result as the table - 14.04 ml of the
stock solution for 5 US gallons (if you use imperial gallons, just
recalucate for 6 US gals).

Otherwise, sulfite added to the must before fermentation will be
pretty much gone after the ferment, so it won't protect your wine for
long term aging. You need to make the sulfite addition after the
ferment (or ML ferment if you go that route).

White crystals in the carboy sounds like "wine diamonds", i.e.,
tartaric acid precipitating out as cream of tartar - normal occurrence
for high acid wines. From what you're saying, I doubt your wines go
through ML but you can always make sure by doing a chromatography
test. Otherwise, just way until the wines taste the way you like them
and sulfite then - but don't wait with that too long, the April date
you mentioned is about as far as you can stretch it. But I would
recommend making sure about the ML - because if your wines are not
going through it, you can and should sulfite right after the ferment
is over, during the first racking.

Pp