Hanna Instruments 

The HI84100-53 acid reagent is necessary to lower the pH of the wine sample before a titration can be performed for free sulfur dioxide. The adjustment of the wine sample with 5 mL of the HI84100-53 acid reagent ensures the sample is at the correct pH. The HI3148B ORP electrode is used to detect the endpoint. The HI84100 can be used with all wines, including red, which are difficult to test using traditional methods due to the difficulty to observe a distinctive color change when the endpoint is reached.

The HI84100 determines the free and total sulfur dioxide concentration in wine using the Ripper method. Excess iodide is added to the wine sample and reacts with the iodate titrant to produce iodine:

IO₃^- + 5I^- + 6H⁺ → 3I₂ + 3H₂O

The iodine produced reacts with sulfur dioxide in the wine according to the redox reaction below:

H₂SO₃ + I₂ → H₂SO₄+ 2HI