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Chemical Analyses: Solids: pH
The saturation paste extract method is one of the most commonly
used laboratory procedures for measuring soil pH. The soil sample
is saturated with distilled water and mixed to a paste consistency.
After mixing, the sample should be allowed to stand for an hour
or more. The paste should be checked to make sure it is still saturated
but free from water collected on the soil surface. The saturated
soil paste is then transferred to a filter funnel with a filter
paper in place and a vacuum is applied. The extract obtained through
the funnel is measured for pH by inserting a standard electrode
and a reference electrode into the extract. A voltage is measured
between the two electrodes which is proportional to the activity
(concentration) of H+ ions and gives a pH value. See methods 2,
3a, and 21a for more detail in the Agriculture
Handbook No. 60 (1969). For more information on pH and measurement
using standard and reference electrodes, see the pH Section (link
to the pH section).
Chemical
Analysis | Physical
Properties |
