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FORMAZIN STOCK SOLUTIONS
The turbidity calibration curve for this instrument was prepared by using formazin
solutions as a reference. A 4000 FTU standard solution is available (Order Code 6195-H,
60 mL) that can be diluted with low turbidity water to prepare solutions within the test
range.Dilutions from this stock solution should be prepared fresh daily with low turbidity
water.
Alternatively, a stock turbidity solution of 400 NTU can be prepared by observing safety
precautions and carefully following the procedure below.
Preparation of Formazin Stock Solution
1. Dissolve 1.000 g of Hydrazine Sulfate in deionized water and dilute to the mark in a
100 mL volumetric fl ask.
2. Dissolve 10.00 g of hexamethylenetetramine in deionized water and dilute to the
mark in a 100 mL volumetric fl ask.
3. Mix 5 mL of each solution in a 100 mL volumetric fl ask and allow to sit undisturbed
for 24 hours at 25 ±3 °C.
4. At the end of the waiting period, dilute to the mark with deionized water and mix.
Store in amber glass.
5. The concentration of this stock solution is 400 FTU. This stock solution is stable for
one month. Dilutions from this stock solution should be prepared fresh daily with
low turbidity water.
COD3 Plus Colorimeter 10.16
Turbidity
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