Stoichiometry and chemical metrology: Karl Fischer reaction

 Stoichiometry of analytical reactions is discussed as an important element of many primary methods (gravimetry, volumetry, spectrophotometry, etc.) and therefore, of chemical metrology as a whole. Variations in stoichiometry caused by non-equilibrium conditions, by changes in the reaction medium or by other factors can be a source of the dominant uncertainty component in the analytical measurement. Such a situation is illustrated with the Karl Fischer (KF) reaction which is widely used in aquametry. Two kinds of solvents used as a part of the reaction medium – alcohols and amides – are compared. The influence of the media on the stoichiometry of the reaction and, correspondingly, on the titre of the KF reagent is evaluated. Received: 4 November 1998 · Accepted: 22 December 1998