Sulfite Calculator
Definition: Sulfite is determined iodometrically by titrating an acidified sample with standardized potassium iodide-iodate solution. The endpoint is detected by the appearance of the blue iodine-starch color.
Sulfite (mg/L as SO₃²⁻) =
[(A − B) × M × 40,000] / V
A = titrant used for sample (mL)
B = titrant used for blank (mL)
M = molarity of KI-KIO₃ titrant (mol/L)
V = sample volume (mL)
Method basis: Standard Methods for the Examination of Water and Wastewater, Method 4500-SO₃²⁻ B — Iodometric Method. With 0.0125 M KI-KIO₃ titrant, 1.00 mL is equivalent to 0.500 mg SO₃²⁻.