AbstractAn account is given of the methods used in quantitative spectrochemical analysis, special attention being paid to the modern procedures using step weakeners: the “Zweilinienverfahren” and the Breckpot step sector method. The merits of both procedures are discussed, from which it follows that the sector method has some advantages over the former. Special problems, however, arise when the sector is used in combination with intermittent light sources (spark, interrupted arc). In this case stroboscopic effects are to be feared, which give rise to erratic values of the extinction caused by the sector. The only instance known in which the occurrence of such effects is claimed ‐ a paper by Pestemer and Schmidt ‐ is subjected to a mathematical treatment in order to check these claims. The results indicate that stroboscopic effects may indeed be observed, if only very conditionally, but that the experimental data on which Pestemer and Schmidt base the above mentioned claims are not in accord with the theoretical expectations. From these and other considerations optimum conditions for the use of the step sector in combination with intermittent light sources are derived, which are confirmed by exp