54 



FLUORESCENCE SPECTROPHOTOMETRY 



transmission of the monochromator with wavelength. The cam takes 

 care of most of the corrections, but some residual errors are later 

 removed by another attenuator drive by a photoelectric curve fol- 

 lower. The residual correction curve is put on a frosted Incite drum 

 with a soft pencil and can easily be adjusted. The corrected electrical 

 signal, now proportional to the intensity of the light emitted from 

 the sample at each wavelength, is separated from random noise by 



FIRST ORDER 

 COUNTER 



WATER COOLED HIGH PRESSURE 

 MERCURY LAMP 



SCALE.; 



' 



12 3 4 5 INCHES 



Fig. 2. Transmission grating monochromator used for producing the incident 

 light. 



means of a 120^ tuned amplifier, rectified to direct current and used 

 to drive the pen of a Brown recorder. The paper in the recorder is 

 moved synchronously with the wavelength drive by means of a Selsyn 

 motor. It is therefore possible to vary the speed of wavelength sweep 

 through various parts of the spectrum during a run. 



The monochromators are designed for high light gathering 

 power and are built with approximately 10 by 10 cm gratings. The 

 monochromator. Fig. 2, used to isolate the incident light has a replica 

 grating with a blaze angle producing a high eflBciency in blue. The 

 wavelength setting of this instrument is read directly on a counter. 

 Figure 3 shows the arrangement of the incident and the fluorescent 

 beams as well as the calibrating lamp. The color sensitivity correction 

 cam and the final correction curve are made with light from a stand- 



