LaMotte DCL-20 Colorimeter - Manual (Page 13)

TITRATION B, CALCIUM
1. Fill the test tube (0778) to the 5 mL line with the diluted soil extract. Dilute to 10 mL with deionized water.
2. Add 2 drops of *Inhibitor Solution (9258).
3. Add 2 drops of *TEA Reagent (3921).
4. Add 8 drops of *Sodium Hydroxide w/Metal Inhibitors (4259).
5. Add one Calcium-Hardness Indicator Tablet (T-5250) to the test sample. Cap and shake to dissolve the tablet. A red
color will develop.
6. Immediately titrate the sample. Fill the Direct Reading Titrator with Standard EDTA Reagent (5254). Insert the tip of
the Titrator into the hole in the cap of the test tube.
7. While gently shaking the tube, slowly press the plunger to titrate until the red color changes to a clear blue and does
not revert to red upon standing 1 - 2 minutes.
8. Read the Titrator scale at the tip of the plunger and multiply by 5.16. This is Titration Value B.
FINAL RESULTS
Calcium Content = 0.4 x Titration Value B = ppm Ca
Magnesium Content = 0.24 (Value A - Value B) = ppm Mg
Multiply the results by 2 to obtain the content in pounds per acre.
EX AM PLE:
Titration Value A is 640 ppm CaCO
3
Titration Value B is 520 ppm CaCO
3
Calcium = 0.4 x 520 = 208 ppm Ca
= 208 x 2 = 416 lb/acre Ca
Magnesium =0.24 (640-520)
= 0.24 x 120 = 29 ppm Mg
= 29 x 2 = 58 lb/acre Mg
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1985-01 • 10/01