The Decomposition of Acidic Karl Fischer Reagent in MethanolThe reaction between sulfur dioxide and iodine in methanol is started by traces of water in the solvent. Hydrogen iodide is formed and reacts with methanol to produce more water until all iodine is used up. An addition compound between iodine and hydrogen sulfite was found as an intermediate and characterized by Raman spectroscopy. Elementary sulfur is formed in a second reaction.