LaMotte COD Plus Colorimeter 1922-EX2 - Manual (Page 125)

PROCEDURE
1. Press and hold ON button until colorimeter turns on.
2. Press ENTER to start.
3. Press ENTER to select TESTING MENU.
4. Select ALL TESTS (or another sequence containing 28 Turbidity)
from TESTING MENU.
5. Scroll to and select 28 Turbidity from menu.
6. Rinse a clean tube (0290) with deionized water (turbidity free). Fill to the
10 mL line with deionized water.
7. Insert tube into chamber, close lid and select SCAN BLANK.
8. Rinse a second clean tube (0290) with sample water. Fill to the 10 mL line
with sample. Cap tube. Wipe off excess water and fingerprints. Shake to
resuspend particulate matter. Remove all bubbles before measurement.
9. Insert tube into chamber, close lid and select SCAN SAMPLE. Record
result. Turbidity measurements should be taken as soon as possible after
sample has been collected.
10. Press
OFF button to turn colorimeter off or press EXIT button to exit to a
previous menu or make another menu selection.
NOTE: For the most accurate results, the sample should be at 25±4°C.
PREPARING FORMAZIN SOLUTIONS
The turbidity calibration was prepared by using standard formazin solutions as
a reference. These solutions can be prepared by carefully following the
procedure below.†
1.
Dissolve 1.000 g of Hydrazine Sulfate in deionized water and dilute to
mark in 100 mL volumetric flask.
2. Dissolve 10.00 g of Hexamethylenetetramine in deionized water and
dilute to mark in 100 mL volumetric flask.
3. Mix 5 mL of each solution in a 100 mL volumetric flask and allow to set
undisturbed for 24 hours.
4. At the end of the waiting period, dilute to mark with deionized water and
mix.
5. The turbidity of the stock solution is 400 FTU. The stock solution is stable
for one month. Dilutions from the stock should be prepared fresh daily.
†Alternatively, a prepared concentrated formazin standard of 4000 NTU may
be ordered in a 60 mL size by Code 6195-H.
TURBIDITY 2/2 COD PLUS TEST PROCEDURES 6/02