42
SECTION 3, continued
3.6.2.4 Preparing Formazin Dilutions (Factory recommended)
Hach Company recommends using 20, 100, and 800 NTU formazin
standards for calibrating the 2100P Turbidimeter. Dilutions with other
NTU values can be prepared and used (see Section 3.6.3.1 on page 48).
If problems occur when using alternate solutions, use the dilutions
specified here.
Prepare all formazin dilutions immediately before use and discard after
calibration. The 4000 NTU solution is stable for up to a year, but
dilutions deteriorate more rapidly. Use the same high quality water
(turbidity <0.5 NTU) for the dilutions and the blank.
1. Attach the syringe
to the 3-way valve by
gently twisting the
square end into the
syringe tip. Attach the
connector, tubing and a
0.2 micron filter (clear
part faces syringe) as
shown. Be sure the
connections are tight.
2. Fill a beaker or
container with the water
to be filtered. Insert the
tubing into the container.
Slowly draw the water
into the syringe by
pulling up on the
syringe plunger.
3. Draw about 50 mL of
sample into the syringe.
Slowly push on the
plunger to force the
water through the filter
and into a graduated
cylinder or volumetric
flask. Repeat Steps 2
and 3 until the desired
amount of water is
obtained.
Note: As the filter clogs, it
gets more difficult to push
water through it. At this
point, discard the filter
and attach a new filter.
Replacement filters are
available in packages of 10
(Cat. No. 23238-10).
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