Free SO2 needed to achieve

                            Whites                         Reds

pH      .8 Molecular         .5 Molecular


11 ppm

7 ppm


13 ppm

8 ppm


16 ppm

10 ppm


21 ppm

13 ppm


26 ppm

16 ppm


32 ppm

20 ppm


40 ppm

25 ppm


50 ppm

31 ppm


63 ppm

39 ppm



Wine           25 ppm              50 ppm            100 ppm

Volume    Total SO2          Total SO2 Total SO2

                (K. Meta) (5% SO2)    (K. Meta) (5% SO2)    (K. Meta) (5% SO2)

750 ml .04 g .38 ml .08 g .75 ml .15 g 1.5 ml


.19 g 1.89 ml .37 g 3.75 ml .76 g 7.6 ml


.95 g 9.46 ml 1.89 g 18.90 ml 3.78 g 37.8 ml
50 gallon 9.46 g 94.60 ml 18.90 g 189.00 ml 37.80 g 378.0 ml
60 gallon 11.30 g 113.50 ml 22.70 g 227.00 ml 45.40 g 454.0 ml
100 gallon 18.90 g 189.00 ml 37.80 g 378.00 ml 75.70 g 757.0 ml


Assume at pH 3.5: 50% is bound and 50% remains as free SO2

at pH 3.1: 25% is bound and 75% remains as free SO2

5% Sulfite Solution = 10 grams K.Meta in 100 mls water = 378.5 grams in 3785 mls (one gallon) water

1 oz = 28.35 grams 1 gallon = 128 fl oz = 3.79 liters = 3785 ml

1 lb = 16 oz = 453.59 grams 1 liter = 1000 ml

milligram/liter = parts per million grams/100 ml = parts per thousand

General suggestions:

The correct amount of SO2 to add, after M/L, is relative to your pH.

Assuming you've corrected your pH to about 3.2 for whites and about 3.5 for reds after M/L, maintain about 25 ppm free SO2 until bottling.

At bottling, you may want to increase your free SO2 by 5-10 ppm.

After bottling, free SO2 drops about 10-15 ppm during the first two months. Especially important for wines you expect to age for a longer time, reducing browning with time.

Wines not properly corrected for pH, if high, will require a lot more SO2, increasing the total, affecting the taste, and not protecting the wine.

Dose: See chart. A gross correction is: 1/4 teaspoon of Sulfite powder per 5 gallons = 25 ppm free SO2 / 50ppm total SO2. 5 Campden tablets = 1/4 teaspoon Sulfite.

(Small amounts of sulfite bind rapidly, loosing effectiveness and increasing the total SO2. Add larger amounts less often to achieve desired levels)

"The use of Sulfur Dioxide depends on fruit composition and condition, general sanitation, and the kind of wine produced. Additions at the crusher favor wine yeasts over spoilage organisms and also inhibit oxidative or browning enzymes in the must. The dose is nearly completely bound during fermentation, chiefly by acetaldehyde. Thus, more needs to be added after fermentation to maintain sufficient free SO2 to prevent spoilage.

The proper level of molecular SO2 will vary with temperature, ethanol content, micro-nutrient levels, and sanitation conditions of the stored wine. For normal circumstances, 0.8 ppm is recommended for whites and 0.5 ppm for reds. If preventing M/L in reds, maintain 0.8 ppm molecular.

While it is doubtful that phenolic substances have much direct microbial toxicity, their affinity for oxygen and other nutrients may render red wines more microbially stable.

The wine's pH affects sulfite concentration/effectiveness. Although the proportion of sulfite is always quite small, it varies tenfold over the pH range of wine (see chart). Oxidation of sulfite to sulfate has a first-order dependence on the sulfite concentration. High pH wines lose free SO2 quite rapidly. In such wines, SO2 at any level is no substitute for methods that lower pH.

If buffer capacity and TA are low, acid addition may lower pH sufficiently. Tartaric acid gives the largest pH shift for a given TA rise. Cold stabilization will lower pH still further if the pH is below 3.6.

Conversely, procedures which at successful under quite low pH conditions, such as eliminating SO2 at crush, may not be appropriate with musts and wines of higher pH, which are more prone to oxidation and spoilage."

By Clark Smith