LaMotte TL-2 Turf Lab Soil Test Kit - Manual (Page 7)

CAL CIUM AND MAG NE SIUM
The Schwarzenbach EDTA titration method, used to determine calcium and
magnesium, involves two titrations. The first titration gives the combined
calcium and magnesium content and the second gives the calcium content.
Magnesium is calculated from the difference between the titration values.
Read LaMotte’s Direct Reading Titrator Manual before proceeding.
DI LU TION OF SOIL EX TRACT
Using the 25 mL graduated cylinder (0417), measure 10 mL of the soil filtrate
and transfer it to a 50 mL beaker (0944). Add 10 mL of deionized water, mix
and neutralize according to the procedure previously described.
TI TRA TION A, CAL CIUM & MAG NE SIUM
1. Fill the test tube (0778) to the 5 mL line with diluted soil filtrate. Dilute
to the 10 mL line with deionized water.
2. Add 5 drops of Calcium Magnesium Inhibitor Reagent (3922). Wait 5
minutes. Swirl to mix.
3. Add 5 drops of *Calcium-Magnesium Buffer (5126). Swirl to mix.
4. Add 10 drops of *CM Indicator (6522). Swirl to mix. Solution will turn
red.
5. Fill the Direct Reading Titrator (0384) with Standard EDTA Reagent
(5254). Insert Titrator tip into the center hole of the test tube cap.
6. While gently swirling the tube, slowly press the plunger to titrate until red
color changes to blue.
7. Read the Titration scale at the tip of the plunger. Multiply by 5.16. Record
as Titration Value A.
TI TRA TION B, CAL CIUM
1. Fill test tube (0778) to the 5 mL line with diluted soil filtrate. Dilute to 10
mL line with deionized water.
2. Add 2 drops of *Inhibitor Solution (9258). Swirl to mix.
3. Add 2 drops of *TEA Reagent (3921). Swirl to mix.
4. Add 8 drops of *Sodium Hydroxide Reagent with Metal Inhibitors (4259).
Swirl to mix.
5. Add one Calcium Hardness Indicator Tablet (T-5250) to the test sample.
Cap and mix until tablet disintegrates. Solution will turn red.
6. Fill the Titrator with Standard EDTA Reagent (5254). Insert Titrator tip
into the center hole of the test tube cap.
7. While gently swirling 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. Multiply by 5.16. Record
as Titration Value B.
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