This International Standard specifies a potentiometric Karl Fischer titration method for the direct determination of water in crude petroleum. It covers the range 0,05 % (m/m) to 2,00 % (m/m) water in crude petroleum containing less than 0,05 % (m/m) but more than 0,005 % (m/m) of either mercaptan sulfur or sulfide ion sulfur or both. It covers the range 0,02 % (m/m) to 2,00 % (m/m) water in crude petroleum containing less than 0,005 % (m/m) of either mercaptan sulfur or sulfide ion sulfur or both. NOTE 1 A number of substances and classes of compounds associated with condensation or oxidation-reduction reactions interfere in the determination of water by Karl Fischer titration. However, the only likely interfering substances present in crude petroleum are mercaptans and ionic sulfides. At levels less than 0,05 % (m/m) as sulfur the interference is insignificant when determining water in the range 0,05 % (m/m) to 2,00 % (m/m). NOTE 2 For the purposes of this International Standard, the terms "% (m/m)" and "% (V/V)" are used to represent the mass and volume fractions respectively.