LaMotte SMART 2 Electronic Soil Lab - Manual (Page 52)

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NEUTRALIZATION OF SOIL FILTRATE
In the test procedures for Ammonia Nitrogen, Calcium & Magnesium,
Copper, Iron, Manganese and Zinc require that the acidity of the soil extract
be neutralized before the test procedure is performed. This is done by adding
*Sodium Hydroxide, 15% (7886) to the soil extract until Bromthymol Blue
Test Paper (2931) indicates that the pH is in the proper range.
1. Add one drop of *Sodium Hydroxide, 15% (7886) to the soil extract. Stir
with the stirring rod.
2. Touch the stirring rod to the Bromthymol Blue Test Paper (2931).
3. If the test paper does not change from yellow to blue or green, continue
adding *Sodium Hydroxide, 15% to the soil extract, one drop at a time. Stir
and test the pH after the addition of each drop until the test paper changes
from yellow to green or blue.
52 SMART2 SOIL MANUAL 1.07