Lowpressuredischargelamps containing mercury, cadmium or zinc. Some spectrophotometers contain lamp housings for these lamps (Hg, Cd, Zn). Where this facility is provided, wavelength checks can be made very
conveniently by operating the discharge lamp and rotating the monochromator to isolate the emitted
spectral lines.For this and all wavelength calibrations the minimum slit width should be used. The mercury lamp has the advantage that its emission spectrum contains several lines over a reasonable range of wavelength. Wavelengths in air of prominent spectral lines of these elements are listed in