From a pure chemistry standpoint, titration to pH=8.2 will yield the more
"correct" value for TA. The reason is that wine is a buffered solution.
When you titrate using NaOH, you are neutralizing the weak organic acids in
the wine (Tartaric, Malic, Lactic, etc.) with a strong base, namely NaOH
(Sodium Hydroxide). The result of this neutralization reaction is things
like Sodium Tartrate, Sodium Malate, etc. These compounds are referred to
as salts. A salt that is formed from a strong base and a weak acid will
itself be slightly basic (pH>7.0), likewise, the salt of a weak base and a
strong acid would be slightly acidic. During titration, you are
neutralizing the weak acids and forming salts which are slightly basic. So,
when you have neutralized all the organic acids in the wine by titration
(which is the definition of determining Total Acid (TA)), all you have left
is a bunch of salts of weak acid/strong base which are slightly basic and
give a pH~8.2, slightly basic.

CHEERS!

"Tom S" > wrote in message
...
>
> "D. J. Gooding" > wrote in message
> ...
> >
> > I recently got a pH meter and want to use it also as a titration
indicator
> for
> > TA measurements. I would have supposed that the desired endpoint pH
would
> be
> > 7.0 (neutral). However, I have found one reference that says to use
8.1 -
> 8.2
> > as the endpoint. Another reference says that it is conventional to use
> 8.2 in
> > the US and 7.0 in France. Does anyone know why? Which yields the TA
that
> I
> > really want to use?
>
> If I remember correctly, the 8.2 pH number comes from where
phenolphthalein
> changes from colorless to pink.
>
> FWIW, I haven't even bothered to measure TA on my wine/juice/must for the
> past 15 years or so. I watch the pH very carefully though. That's the
> number that really counts in the long term.
>
> Tom S
>
>