Effect of Hydrocarbon Composition on the Measurement of Water in Oils by Coulometric and Volumetric Karl Fischer Methods

The effect of the composition of hydrocarbons and hydrocarbon mixtures such as oils on the measurement of their water content has been examined. This effect has been evaluated by both the coulometric and volumetric Karl Fischer methods. The results demonstrate that the highest water titers are measured by the volumetric method. With the exception of xylene and octanol, the water titers obtained by at least one coulometric method were lower than those obtained by the volumetric method. The water content of xylene and octanol was equivalent by all methods. The solubility of the oils in the titration vessel solvents was evaluated as a function of the hydrocarbon composition and the content of cosolvents. The formation of a heterogeneous solution caused a decrease in the observed water titer, with the exception of several transformer oils. At the transition point from a homogeneous solution to a heterogeneous solution, frequently no water was measured in at least one sample. The reduction of the water titer at the point that the vessel solution became heterogeneous is consistent with the sequestering of some of the water by suspended oil.