CHECKS WITH ASSISTANCE.
If a medical facility, testing laboratory, or other
military unit which may have cobalt chloride solution and neodymium
chloride solution, is convenient, the following two checks will cer-
tify the accuracy of the spectrophotometer.
Instrument Linearity Check.
To determine if your instrument is
giving a linear response and to insure that the instruments optical
system is functioning properly, the following procedure may be used.
(1) Fill a clean 50 ml graduate cylinder to the 25.0 mark with
cobalt chloride solution.
Fill the graduated cylinder to a final
volume of 50.0 ml with demineralized water.
(2) Repeat step 1 using 20, 15, and 5 ml of cobalt chloride
solution and filling each graduated cylinder to a final volume of 50
ml with demineralized water.
(3) Insert the % transmittance - absorbance meter scale in the
meter and adjust the wavelength dial to 510 nm.
(4) Fill a sample cell with demineralized water, place it in the
cell holder and set the meter to read 100% T or O absorbance.
(5) Place the sample prepared in step (1) in the cell holder and
read the absorbance value from the meter scale.
(6) Repeat step (5) using the dilutions prepared in step (2).
(7) Graph the results on linear paper, plotting the ml
chloride solution used for each sample versus the absorbance
obtained in figure 3-1.
The results should be a straight line passing
through zero as shown by plot A on the graph (fig
Deviations from a straight line such as
plot B may be caused by stray light due to light
leakage, optical imperfections or improper optical
alignment and maintenance.
Turn improper perform-
ing instruments in for a replacement.
Instrument Wavelength Accuracy Check.
setting on your DR/2 spectrophotometer may be checked in the
(1) Turn the spectrophotometer on and adjust the wavelength dial
to 575 nm.
Insert the % transmittance - absorbance meter scale in the
(2) Fill a sample cell with neodymium chloride solution and
place it in the sample cell holder.