# Why is sulphuric acid added in the ripper titration?

Ripper titration can be used to determine free $\ce{SO2}$ in wine by titration with iodine.

The method requires sulphuric acid to be added to wine before titration. Why is this the case?

• sulfur dioxide (molecular) $$\ce{SO2}$$ ,
• Bisulphite $$\ce{HSO3-}$$
• Sulphite $$\ce{SO3^2-}$$
$$\ce{SO2 + I2 + 2H2O → H2SO4 + 2HI}$$