Sulfur dioxide: quantity and effect

The standard

The pH-dependent active fraction gauges sulfur dioxide not by the quantity added, but by the share that, at the prevailing pH, is present in molecular and therefore effective form.

Criteria

• The quantity added divides into free and bound sulfur dioxide
• Of the free share, only the molecular form is effective
• The pH value determines how large this molecular share is
• Bound sulfur dioxide contributes nothing to protection

Distinction

Sulfur dioxide ≠ sulfites: sulfur dioxide is the added compound, sulfites are its forms bound within the wine. Sulfur dioxide ≠ total sulfur: the total figure sums free and bound forms, whereas the pH-dependent active fraction alone describes the actual protection.