A double-beam method of spectral selection with flames

Summary A non-dispersive, optic-electrical filter instrument is described, which combines high spectral resolving power (∼0.1 ?) with large luminosity, at wavelengths which are of interest in spectrochemistry. The method is based on the balance of two light-beams emitted by a source S, which are periodically chopped in opposite phase. By placing a flame A containing vapour of some element into one light-beam, this balance is made critical for wavelengths that are specifically absorbed by this vapour. The applicability of a self-radiating flame as absorber could be realized by making use of an a.c. measuring device and by choosing a suitable position of the light-chopper. The described test experiments, which were made with a provisional instrument, prove the applicability of this method, especially in flame photometry.