An Improved Technique for Measuring Soil pH

Soil solution is obtained by immiscible displacement using centrifugation in the presence of an excess of carbon tetrachloride. A combination glass electrode is then introduced into the soil solution which is floating on top of the carbon tetrachloride. By keeping the system closed, changes in pH induced by loss or gain of carbon dioxide are avoided. No water need be added to a naturally occurring soil so changes in pH induced by the dilution effect and/or the salt effect are obviated. There is no contact between reference electrode and soil particles so there is considered to be no junction error involved in the measurement. The technique is simple and reasonably convenient; the readings are stable and apparently reliable.