An automatic photoelectric analyzer, the counterpart of infrared process-stream analyzers, has been developed for recording the concentration of an ultraviolet-absorbing component in a nonabsorbing mixture of liquids or gases. Radiation sources, filters, and phototubes are interchangeable to provide various monochromatic radiations, or a simple monochromator can be attached to provide any wavelength from 220 to 1200 mμ. The concentration range of the analyzer can be selected by choice of interchangeable cells of lengths from 0.001 to 7.5 in., and by choice of shutters of various absorbance ranges in an optical balancing system. The absorbance range is usually restricted to values between 0.01 and 0.2. Sustained high accuracy is achieved by employing a ratio-detecting, phototube bridge circuit that eliminates erroneous readings caused by source fluctuations, and by employing an automatic standardizing system that periodically restores the initial calibration of the instrument and compensates for drift caused by fouling of windows of the sample cell and for other commonly encountered drifts. High concentrations, on the one hand, or concentrations in parts per million, on the other, can be recorded, and several typical applications are listed.
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