Hach DR/850 Procedures Manual page 128

CHLORINE, TOTAL,
9.
When the timer
beeps, place the
AccuVac Ampul into the
cell holder. Tightly
cover the ampule with
the instrument cap.
Sampling and Storage
continued
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L total chlorine
will be displayed.
Note: If the sample
temporarily turns yellow
after sample addition, or
the display shows "limit",
it is due to high chlorine
levels. Dilute a fresh
sample and repeat the test.
A slight loss of chlorine
may occur during dilution.
Multiply the result by the
appropriate dilution factor;
see Section 1.
Analyze samples for chlorine immediately after collection. Free
chlorine is a strong oxidizing agent, and it is unstable in natural
waters. It reacts rapidly with various inorganic compounds and
more slowly oxidizes organic compounds. Many factors,
including reactant concentrations, sunlight, pH, temperature and
salinity influence decomposition of chlorine in water.
Avoid plastic containers since these may have a large chlorine
demand. Pretreat glass sample containers to remove any
chlorine demand by soaking in a dilute bleach solution (1 mL
commercial bleach to l liter of deionized water) for at least 1
hour. Rinse thoroughly with deionized or distilled water. If
sample containers are rinsed thoroughly with deionized or
distilled water after use, only occasional pre-treatment is
necessary.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
128