PURPOSE:To make simultaneous photometry possible in a wavelength range from ultraviolet rays to visible rays without damaging sensitivity by providing the seconds spectroscopic means besides the first spectrocopic means to limit the wavelength range of light incident on the inside of a sample chamber. CONSTITUTION:A zero-dispersive double spectroscope using concave diffraction gratings 8 and 10, a main spectroscope with a concave diffraction grating 16 as the center and a sample chamber 14 are included in a spectroscopic unit 1. Ultraviolet rays radiated from a heavy hydrogen lamp 2 are made incident on the inside of the double spectroscope from an incidence slit 6 and pass a mirror 7 and are made incident on the grating 8. The rays of light having a specific wavelength range out of the light dispersed by the grating 8 pass an intermediate slit 9. This light is dispersed again by the grating 10 and its direction is opposite to that of the light dispersed by the grating 8 and the ray of light are condensed to one position in the position of an exit slit 11. However, this light is not a completely white light because the wavelength range is already limited by the slit 9. The ray of light passing the slit 11 pass a flow cell 15 and are made incident on the grating 16. Meanwhile, visible rays from a tungsten lamp 3 pass a mirror 12 and are directed to the grating 10.
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