The stoichiometry in the determination of water using Karl Fischer reagent

The stoichiometry of the Karl Fischer reaction is not unambiguous. The titer of a Karl Fischer solution rises with the amount of water, because sulphur trioxide which is formed as an intermediate consumes water too. An 1:1-stoichiometry (H2O:I-2) can be simulated by alcohols, because these solvents also react with iodine and sulphur dioxide leading to additional consumption of iodine during the titration. This interpretation of the results of Karl Fischer titrations is supported by the isolation or identification of pertinent reaction products.