As I understand it the scales were developed using pure sucrose and
pure water so unless they specifically state it I would say no
compensation is made for any other dissolved solid (such as acid).

Table sugar is at least 99.5% pure sugar as a FWIW. The reference I
use is from the US NBS (now NIST). Polarimetery, Saccharimetry and
the Sugars by Bates et al. NIST refered me to it when I asked a
similar question of them; it's what they used at the time.
Joe

Are the single scale
BRIX hydrometers some folks use calibrated for sugar/water
solutions ?? (eg. No compensation for the acid found in wine
musts) Or are they calibrated for winemaking by incorperating
an allowance for acid in the BRIX calculation thus making them
a "direct read" instrument ?? TIA