The equivalence point (amount of acid = amount of sodium hydroxyde)
depends on the acids present and their relative amounts. For tartaric
acid it will be at about pH=8,5. For malic acid it would be about
pH=9,8. In a mixture of acids (wine) it will be very difficult to even
find the exact equivalence point even if you obtained the full
titration curve, but such a curve will give the best indication.
To simplify this a titration standard is used. The exact pH value does
not become very important as long as it is in the range 7 - 9. The
selected value of pH=8.2 Is probably a practical choice since the
commonly used indicator phenolptalein starts its colour shift to red
at this point.
Why the Europeans selected pH=7 is perhaps because this represent the
value for pure water. Strictly all titrations require a correction for
the titration error made by using an indicator with colour change at a
different pH than the "equivalence" point of the acid(s). For the US
standard this error is negligible when using phenoltalein.

Greg Cook > wrote in message ws.com>...
> On 3/25/04 5:24 PM, in article
> , "Joe Sallustio"
> > wrote:
>
> > Stop at the permanent color change.
> >
> > Can someone please give me insight regarding the end
> >>>> point color I should be watching for? A red will gradually turn to a
> >>>> reddish-gray,
> >
> > The Europeans use 7 as the endpoint, North Americans use 8.2. I have
> > noted it's not that big a difference just as Greg mentioned, the PH
> > really takes off around 7. I use 8.2
>
> Yup - I suspect that is because the European standard for TA is based on
> Sulfuric Acid (H2SO4) rather than Tartaric Acid. Can anyone enlighten me on
> that one?
>
> Thanks.