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a different molecular weight (150.9 for tartaric, 134.1 for
malic and 192.1 for citric), but a mole of each is neutralized
by two moles of sodium hydroxide, what winemakers have
standardized upon is interpreting the results of the tests as
though the acid being neutralized were tartaric. Likewise,
wine makers don't usually like to think in terms of moles, so
the results are converted via a multiplier into the more
familiar “parts per thousand.” So acid measurements of wine
must are provided in terms of TA (titrateable acidity) as
tartaric in PPT (parts per thousand). This is the same thing as
grams per liter, abbreviated as g/L.
The method of measuring the acid content is called titration,
and it takes advantage of the fact that acids and bases
neutralize each other. You might have observed this
phenomenon as a kid by mixing baking soda with vinegar.
The combination generated carbon dioxide gas initially, but
after a while settled down and did nothing once either
component was fully neutralized. We won't be using baking
soda because we don't want to generate gas. Instead, we'll
use a standardized solution of sodium hydroxide—otherwise
known as lye.
The widely available acid test kits have a problem. That is,
they rely upon the color change of an indicator
(phenolphthalein) which turns pink when enough sodium
hydroxide has been added. But if you are dealing with a pink,
blue, or purple sample, ascertaining when it has changed
color is really difficult. I recommend using an inexpensive pH
meter 49 instead.
By using either an indicator that changes color when the
solution has been neutralized or a pH meter, you can tell
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