24
SECTION 2,
continued
2.6.2
Preparing Dilution Water
Dilution water may be required for indexing and matching sample cells, diluting
over-range samples, and/or preparing formazin standards. For turbidity
measurement, an overrange sample can only be diluted with a portion of
filtered sample.
Collect at least 1000 mL of high quality water (e.g., distilled, demineralized, or
deionized water). Check the turbidity of the dilution water before use. The 2100N
Turbidimeter may be used to check the dilution water turbidity because the
instrument is precalibrated at the factory. If the turbidity is greater than 0.5 NTU,
the water may be filtered with a 0.2 micron filter using the Sample Filtration and
Degassing Kit (Cat. No. 43975-10) or the equivalent.
Clean all glassware with 1:1 hydrochloric acid and rinse several times with
dilution water when measuring low range turbidity samples. Cap the cells to
prevent small air-borne particles from contaminating the glassware if it is not
used immediately.
2.6.2.1
Dilution Water Filtration Procedure
1.
Attach the syringe to the
three-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
about 50 mL 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 enough
water is collected.
Note: Pushing water through
the filter becomes more difficult
as the filter clogs. Discard a
clogged filter and attach a new
filter when necessary.
Replacement filters are
available in packages of 10
(Cat. No. 23238-10).
Tài liệu sưu tầm của Trung Sơn - www.tschem.com.vn - 028.3811.9991 - [email protected]
Tài liệu sưu tầm của Trung Sơn - www.tschem.com.vn - 028.3811.9991 - [email protected]
