mg/L
mg/L
0.8 is typical for whites; reds often 0.5–0.6
L
% w/v
Leave as is if you only use PMS
Molecular SO₂ now–
Free SO₂ needed–
Increase required–
PMS to add–
or SO₂ solution–
Status–
Additions assume all the added SO₂ stays free. In practice some of it binds, especially in wines high in acetaldehyde or sugar, so add in stages and re-test free SO₂ a day or two later. PMS figures use its theoretical 57.6% SO₂ yield. pKa 1.81 at about 20 °C.
Free SO₂ needed at each pH
For 0.5 and 0.8 mg/L molecular. Above about pH 3.8 the free SO₂ required becomes impractical, so pH management matters more than more sulphur.
| pH | 0.5 mol. | 0.8 mol. |
|---|
Need a reliable free SO₂ number first?
Free + total SO₂