The application of Landolt reactions in quantitative catalytic analysis

Abstract

The place of Landolt reactions among quantitative catalytic methods is reviewed. By measuring the time lapse of the incubation period of a Landolt reaction (the reaction time) and plotting its reciprocal values versus catalyst concentration, a calibration graph can be obtained. The advantages of the use of Landolt reactions are as follows: there is no need for instrumentation and temperature control is simple. Theoretical backgrounds of the method are presented on a kinetic basis. During the analyses the uncatalysed and the catalysed reactions proceed simultaneously. The uncatalysed reaction can be examined separately if reaction time measurements are taken in the absence of the catalyst. Having obtained the velocity constant of the former, results of measurements of the reaction times of the simultaneous reactions can be evaluated to obtain the velocity constant of the catalysed reaction alone. The experimentally obtained calibration graph shows a linear correlation between reciprocal reaction time versus catalyst concentration; the rigorous kinetic examination, however, yields to a partly exponential correlation. By expanding the exponential member into a Taylor series and examining the error that arises by neglecting the non-linear members the simple linear correlation can be explained. Sensitivity, selectivity and precision of the methods are briefly discussed.