Measurement of Moisture Content (Water Content) in Edible Oil Using the Volumetric Karl Fischer Method According to ISO 8534:1996 Ivo Leito and Lauri Jalukse 1 Description of the Analytical Procedure 1.1 Principle Karl Fischer (KF) titration is based on the following reaction: I 2 + N ⋅SO 2 + 2 N + H 2 O → 2 N H + I _ + N ⋅SO 3 ð1Þ N ⋅SO 3 + ROH → N H + ROSO 3 _ ð2Þ The reaction is very fast and with strict stoichiometry. Solution of iodine, SO2 and pyridine dissolved the alcohol ROH is the titrant solution. In the classical KF titrant the alcohol ROH is methanol. In modern commercial titrants ROH is often methoxyethanol and pyridine is often replaced by imidazole (both because of potential toxicity). Titration is carried out in ROH or in a mixture of ROH and some other solvent (if samples are not soluble in ROH). The end point of the titration is indicated by a small amount of unreacted iodine in solution. End-point is usually determined voltammetrically: alternating current of constant strength is applied to a double Pt electrode. Potential difference between Electronic supplementary material The online version of this chapter (https://doi.org/10.1007/ 978-3-030-20347-4_3) contains supplementary material, which is available to authorized users. I. Leito (&)  L. Jalukse Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia e-mail: ivo.leito@ut.ee © Springer Nature Switzerland AG 2019 N. Hrastelj and R. Bettencourt da Silva (eds.), Traceability, Validation and Measurement Uncertainty in Chemistry: Vol. 3, https://doi.org/10.1007/978-3-030-20347-4_3 45