Preparing Recommended Formazin Dilutions - Hach 2100N Instruction Manual

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SECTION 3,
continued

3.2.3 Preparing Recommended Formazin Dilutions

Note: Instead of diluting a formazin
stock solution, StablCal™ stabilized
formazin suspensions may be used.
Order StablCal Calibration Kit for
the 2100N Turbidimeter, Cat. No.
26621-00 (bottled) or Cat. No.
26621-05 (ampules).
Standard
Add 100 mL of dilution water to
20 NTU a clean 200-mL Class A
volumetric flask.
Add 50 mL of dilution water to
200 NTU a clean 100-mL Class A
volumetric flask.
Add 50 mL of dilution water to a
1000 NTU clean 100-mL Class A
volumetric flask.
Transfer approximately 30 mL of
well mixed 400-NTU Formazin
4000-NTU
stock solution to a clean sample
cell. No dilution is required.
* A class A volumetric pipet may be used in place of a TenSette Pipet.
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Hach Company recommends use of 20-, 200-, 1000- and 4000-NTU Formazin
standards for calibration of the Model 2100N Turbidimeter. Prepare all Formazin
dilutions immediately before calibration, and discard the dilutions after use. While
4000-NTU stock solutions are stable for up to one year, diluted solutions
deteriorate more rapidly. Prepare dilutions of 20, 200 and 1000 NTUs according
to the directions in Table 2,below. The dilution water also is used to make an
initial blank measurement.
Table 2 Formazin Standard Preparation
Step 1
With a TenSette
1.00 mL of well-mixed 4000-FNU
formazin stock solution to the
200-mL flask.
With a TenSette Pipet*, add
5.00 mL of well-mixed 4000-FNU
formazin stock solution to the
100-mL flask.
With a TenSette Pipet*, add
25.00 mL of well-mixed 4000-FNU
formazin stock solution to the
100-mL flask.
Step 2
® Pipet*, add
Dilute to the mark with dilution
water. Stopper and mix.
Dilute to the mark with dilution
water. Stopper and mix.
Dilute to the mark with dilution
water. Stopper and mix.
38
Step 3