LaMotte HESTER SOIL TEST ST-H - Manual (Page 2)

PRO CE DURE
1. Fill a test tube (0204) approximately one-third full of soil. Use the
Model PWB-1 Demineralizer Bottle (1155) to add demineralized
water to the tube, until it is one-half inch from the top. Cap and
shake until the soil is well dispersed.
2. Add 5 drops of Soil Flocculating Reagent (5643). Cap and shake to
mix. Allow contents to settle before proceeding to Step 3.
3. Use a 1 mL pipet (0354) to transfer 1 mL of the clear solution above
the soil to one of the large depressions on a spot plate (0159).
Transfer a second 1 mL sample to the other large depression on the
spot plate.
4. To the first sample on the spot plate, add two drops of *Duplex
Indicator (2221). Compare the resulting color reaction against the
Duplex Color Chart (1313). NOTE: The wide range pH test result
indicates which narrow range indicator and color chart should be
selected to perform a more precise pH test. Choose the narrow range
indicator and appropriate chart with a mid-point that is as close as
possible to the value obtained in the wide range test.
INDICATOR
pH
RANGE INDICATOR
CODE COLOR
CHART CODE
Bromcresol
Green 3.8-5.4 2207 1328
Chlorphenol Red 5.2-6.8 2209 1329
Bromthymol Blue 6.0-7.6 2210 1331
Phenol Red 6.8-8.4 2211 1332
EXAMPLE: If the wide range test result is pH 6.0, choose the Chlorphenol
Red Indicator (2209) & the Chlorphenol Red Color Chart (1329) for
Step 5.
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