Calculators
Molecular SO2 calculator
Work out the free SO₂ a wine needs at its own pH, and how much potassium metabisulfite or sulfite solution adds it, with the working shown.
Bench arithmetic, with the working shown. Nothing here is saved, and none of these numbers is a figure for a label. Each one comes from a working formula with its assumption stated. Bench-trial anything before it goes into a tank.
Molecular SO₂
What protects wine is molecular SO₂, and how much free SO₂ you need to get there depends on pH. A single rule like “add 30 ppm” leaves high-pH wine under-protected.
19354 mg ÷ 57.6 mg/mL = 336 mL of your 10% solution
28 ppm free gets you 0.5 ppm molecular at pH 3.55.
A 10% w/v solution is 10 g of potassium metabisulfite made up to 100 mL. Metabisulfite is 57.6% SO₂ by weight, so each milliliter carries 57.6 mg SO₂. Weigh the salt when you mix it. Don’t estimate it by eye. How to make up the solution.
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