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Free SO2 as a function of pH and molecular SO2.
The pH measurement of your wine affects your SO2 requirements.

Here is a table you can use to determine how much Free SO2 is required to adequately protect your wine from oxydation and bacterial infection, based on its pH reading. Effective protection is provided at about 0.8 mg/L molecular SO2. Maximum protection is achieved at around 2.0 mg/L molecular SO2. This is also close to the level at which SO2 can be detected by the senses.

Note: Milligrams Per Litre and Parts Per Million are effectively the same thing.

How to use this table:

  1. Measure the pH of your wine.
  2. Look up your pH reading in the leftmost column of this table.
  3. Read across the table to determine the minimum and maximum values of Free SO2 you should consider using in your wine.
  4. Go to our SO2 Additions web page to see how to generate the required SO2.

  Free SO2 Free SO2
pH
reading
Minimum effective
protection (0.8 mg/L
molecular SO
2)
Maximum protection
before sensing (2.0 mg/L
molecular SO
2)
2.8 9 23
2.9 12 29
3.0 14 36
3.1 18 45
3.2 22 56
3.3 28 70
3.4 35 87
3.5 44 109
3.6 55 137
3.7 69 172
3.8 87 216
3.9 109 272
4.0 137 342
4.1 172 430
4.2 216 540

This table was provided by Charles Plant.