W. Fischer et K. Beckenkamp, THE DECOMPOSITION OF ACIDIC KARL FISCHER REAGENT IN METHANOL, Journal fur praktische Chemie, Chemiker-Zeitung, 340(1), 1998, pp. 58-61
The reaction between sulfur dioxide and iodine in methanol is started
by traces of water in the solvent. Hydrogen iodide is formed and react
s 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 sulfu
r is formed in a second reaction.