1. What is a SO₂ Calculator for Wine?

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

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 (typically 0.8)
• \( pKa \) — 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 SO₂ Calculation in Winemaking

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, wine pH (default 3.4), conversion factor (default 0.8), and pKa (default 1.81). All values must be > 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. The target range is typically 0.5-0.8 mg/L.

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

Q3: What's a typical conversion factor (k)?
A: The factor is typically 0.8, representing the proportion of free SO₂ that's in the active bisulfite form.

Q4: When should I adjust the pKa value?
A: The pKa of 1.81 is standard for SO₂ in wine, but might vary slightly with temperature and alcohol content.

Q5: How often should I measure SO₂?
A: Measure free SO₂ regularly during winemaking, especially after racking, before bottling, and during storage.