1. What is a Winemaking SO₂ Calculator?

Definition: This calculator estimates the molecular SO₂ concentration in wine based on free SO₂, pH, and chemical properties.

Purpose: It helps winemakers determine the effective antimicrobial concentration of sulfur dioxide in their wine.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( [SO₂] \) — Molecular SO₂ concentration (mg/L)
• \( FSO₂ \) — Free SO₂ concentration (mg/L)
• \( pH \) — Wine pH (dimensionless)
• \( k \) — Conversion factor (dimensionless, typically 1)
• \( pKa \) — Dissociation constant (~1.81 for SO₂)

Explanation: The formula calculates the equilibrium concentration of molecular SO₂, which is the active antimicrobial form.

3. Importance of Molecular SO₂ Calculation

Details: Proper SO₂ management ensures wine stability, prevents oxidation and microbial spoilage, while avoiding excessive additions that could affect wine quality.

4. Using the Calculator

Tips: Enter the free SO₂ concentration (mg/L), wine pH (typically 2.8-3.8), conversion factor (default 1), and pKa value (default 1.81). All values must be valid (pH 0-14, others > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why is molecular SO₂ important?
A: Molecular SO₂ is the active antimicrobial form that protects wine from bacteria and yeast, with 0.5-0.8 mg/L typically needed.

Q2: How does pH affect SO₂ effectiveness?
A: Lower pH increases the proportion of molecular SO₂ at a given free SO₂ level, making SO₂ more effective.

Q3: When would I change the pKa value?
A: The pKa of SO₂ is approximately 1.81 at 20°C. You might adjust slightly for temperature variations (decreases ~0.03 per 10°C increase).

Q4: What's a typical target molecular SO₂ level?
A: Generally 0.5-0.8 mg/L for antimicrobial protection, though this varies by wine style and condition.

Q5: How often should I test and adjust SO₂?
A: Test free SO₂ regularly (monthly during aging) and after any wine movement or blending that might affect pH.