81-71
SUSPENDED SOLIDS, continued
10. Slowly and
gently invert and
swirl the prepared
sample to uniformly
suspend any residue.
Avoid vigorous
mixing which would
introduce gas bubbles
into the sample.
11. Place the
prepared sample into
the cell holder.
Note: Use 10-mL cells
for the blank and the
prepared sample in
bright sunlight. Close
the cell compartment
cover.
12. Press: READ
The display will
count down to 0.
Then the display will
show the results in
mg/L nonfilterable
residue.
SAMPLING AND STORAGE
Collect samples in clean plastic or glass bottles. Analyze as soon as
possible after collection. Samples may be stored for 7 days by cooling
to 4
o
C (39
o
F).
INTERFERENCES
Calibration for this test is based on parallel samples using the
gravimetric technique on sewage samples form a municipal sewage
plant. For most samples, this calibration will provide satisfactory
results. When higher accuracy is required, it is recommended that
parallel spectrophotometric and gravimetric determinations be run using
portions of the same sample. The new calibration should be made on
your particular sample using a gravimetric technique as a basis.
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