LaMotte SMART 3 Electronic Soil Lab - Manual (Page 87)

SMART3 Soil 1.11 87
PROCEDURE
A. PREPARATION OF DILUTE ZINC INDICATOR SOLUTION
Use a pipet (0352) to measure exactly 5.0 mL of *Zinc Indicator Solution 1.
(6314) into 10 mL graduated cylinder (0416). The bottom of the curved
surface (the meniscus) of liquid should be at 5.0 mL mark. Pour this into the
bottle labeled “Dilute Zinc Indicator Solution”.
Use unrinsed graduated cylinder to add 10.0 mL and then 7.8 mL (total of
2.
17.8 mL) of *Methyl Alcohol (6319) to bottle labeled “Dilute Zinc Indicator
Solution”. Cap and mix ingredients in this bottle. Do not leave this bottle
uncapped.
B. DETERMINATION OF ZINC
Press and hold 1. until colorimeter turns on.
Press 2. ENTER to select TESTING MENU.
Select 3. ALL TESTS (or another sequence containing 099 Zinc LR) from
TESTING MENU.
Scroll to and select
4. 099 Zinc LR from menu.
Fill a clean tube (0290) to the 10 mL line with the soil extract then neutralize 5.
according to the procedure on page XXX.
Insert tube into chamber, close lid and select SCAN BLANK. (See Note)
6.
Remove tube from colorimeter. Use 0.1 g spoon (0699) to add one measure 7.
of Sodium Ascorbate Powder (6316). Use 0.5 g spoon (0698) to add one
measure of *Zinc Buffer Powder (6315). Cap and shake vigorously for 1
minute. Some undissolved buffer may remain in the bottom of the tube.
Add 3 drops of *Sodium Cyanide, 10% (6565). Cap and mix.
8.
Use the 1 mL pipet assembly to add 1 mL of “Dilute Zinc Indicator Solution”. 9.
Cap and mix.
Use a second plain pipet (0352) to add 4 drops of *Formaldehyde Solution,
10.
37% (5128). Cap and mix by inverting 15 times.
Insert tube into chamber, close lid and select SCAN SAMPLE. Multiply result
11.
by 5 to determine the zinc concentration in ppm.
Press
12. to turn colorimeter off or press
EXIT
to exit to a previous menu
or make another menu selection.
NOTE: For best possible results, a reagent blank should be determined
to account for any contribution to the test result by the reagent system. To
determine the reagent blank, follow the above test procedure to scan a distilled
or deionized water blank. Then follow the above procedure to perform the test
on a distilled or deionized water sample. This test result is the reagent blank.
Subtract the reagent blank from all subsequent test results of unknown samples.
It is necessary to determine the reagent blank only when a new lot number of
reagents is obtained.