"Charles H" wrote:

Well, the sheet that came with the grapes has 14.2 as the number under
the acid column... I was thinking it was 14.2ppt? However, 1.42 makes
more sense.

You may want to try to verify this with your own test before doing any
adjustments.

The only place I've seen ppt measurements (and that has been very recently)
it was showing the value in terms of sulfuric acid, which I'm told is the
French convention. [The convention I'm familiar with is percentage in terms
of tartaric.] If this is the case (and it may well be if the grapes came
from Quebec), you need to convert to tartaric as a reference for most of the
discussions in this newsgroup to make much sense.

I believe the ratio between sulfuric and tartaric is 1.5, thus:

14.2 ppt sulfuric = 1.42% sulfuric / 1.5 = 0.95 tartaric, which is a more
reasonable figure for ripe grapes.

I'm not sure of this formula, however, because I'm not sure whether
parts-per-thousand is a weight per volume figure, a volume per volume
figure, or something on the molecular level. So I may be mixing apples with
oranges.

Regardless, it is always best to run your own tests, rather than rely on
vineyard or retailers figures. They may be in error for any number of
reasons.