LaMotte SMART 2 - Manual (Page 117)

TOTAL CHROMIUM WITH ACID DIGESTION PROCEDURE
1. Fill graduated cylinder (0418) to 50 mL line with sample water. Transfer
to Erlenmeyer flask (0431).
2. Use the 1 mL pipet (0354) to add 5 mL (five measures) of *Sulfuric Acid,
5N (7681). Swirl to mix.
þ NOTE: Highly buffered waters may require pH adjustment. Adjust the pH
of highly buffered samples to 7.0 ±0.5. Continue procedure.
3. Place flask on burner or hot plate. Bring solution to a gentle boil.
4. Fill pipet (0341) with Potassium Permanganate, 0.5% (7682). While
gently swirling flask, add Potassium Permanganate, 0.5% (7682), 2 drops
at a time to boiling solution, until solution turns a dark pink color which
persists for 10 minutes. Continue boiling.
5. Add one drop of *Sodium Azide, 5% (7683) to boiling solution. Boil for
approximately 30 seconds. If pink color does not fade, add another drop of
*Sodium Azide, 5%. Continue adding *Sodium Azide, 5% one drop at a
time until pink color disappears.
6. Remove flask from heat. Cool sample under running water. This is the
digested sample.
7. Pour digested sample into clean graduated cylinder (0418). Dilute to the
50 mL line with Deionized Water (5115).
8. Press and hold
ON button until colorimeter turns on.
9. Press ENTER to start.
10. Press ENTER to select TESTING MENU.
11. Select ALL TESTS or another sequence containing 22 Chromium)
from TESTING MENU.
12. Scroll to and select 22 Chromium from menu.
13. Rinse a clean tube (0290) with sample water. Fill to 10 mL line with
sample water.
14. Insert tube into chamber, close lid and select SCAN BLANK.
15. Remove tube from colorimeter. Use 0.1 g spoon (0699) to add one level
measure of *Chromium Reagent Powder (V-6276). Cap and shake for one
minute. Wait 3 minutes.
16. During the waiting period, fold a piece of filter paper in half, then in half
again to form a cone. Push corners together to open end, and insert into
funnel (0459).
17. Filter sample into a clean tube (0290). Cap and mix. Insert tube of filtered
sample into chamber, close lid and select SCAN SAMPLE. Record result.
18. Press OFF button to turn colorimeter off or press
EXIT button to exit to a
previous menu or make another menu selection.
Smart2 TEST PROCEDURES 10.04 Chromium–Hexavalent, Trivalent & Total 3/4