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Instructions for Using the Spectronic-20

1. The instrument should be turned on about one half hour before measurements are begun to allow the instrument to stabilize.
   
   
2. Set the desired wavelength.
   
   
3. With no tube in the sample holder and the cover closed, adjust the meter to zero transmittance (infinite absorbance) with the left-hand front knob.
   
   
4. With a tube containing a blank sample (everything but the substance being investigated), adjust the instrument to read zero absorbance (100% transmittance) with the right-hand front knob.
   
   
5. Remove the tube containing blank sample, and make sure that the meter reads zero transmittance.  If it does not, repeat steps 3 and 4.
   
   
6. Substitute a sample to be studied.  Read and record the absorbance without changing any knob settings.