this method depends upon the fact that a solution of sulfur dioxide and iodine in pyridine and methanol reacts with water quantitatively
requires rigid exclusion of atmospheric moisture.
Colorless soln
endpoint of titration may be determined electrometrically or visually by a change from a canary yellow to amber color
Colored soln
endpoint is obscure and is best determined electrometrically
Method I-A (Direct Titration)
Use Karl-Fischer Reagent
1ml of KF reagent = 5mg H2O
Composition of KF Reagent:
iodine
methanol
pyridine
sulfur dioxide
Method I-B (Residual Titration)
excess reagent is added to the test specimen, sufficient time is allowed for the reaction to reach completion, and the unconsumed reagent is titrated with a standard solution of water in a solvent such as methanol
applicable generally and avoid the difficulties that may be encountered in the direct titration
Method I-C (Coulometric Titration)
KF reaction is used
iodine, however, is not added in the form of a volumetric solution but is produced in an iodide containing solution by anodic oxidation.
Method II (Azeotropic-Toluene Distillation)/ Volumetric Method
with the help of toluene moisture apparatus, water may be determined by volume measurement
Azeotropic
a mixture of organic liquids with different boiling temperatures but distilling at a constant temperature