The Effect of Hydrogen-Ion Concentration on the Flocculation Values of Chromic and Aluminum Oxide Sols

A Comparison of Glass and Quinhydrone Electrodes for Determining the pH of Some Iowa Soils: I. A Comparison of Different types of Glass Electrodes1

“…In recent years a number of investigators, notably Karraker (14), 3 McGeorge (zo), Baver (I), Heintze and Crowther (II), and Naftel, Schollenberger, and Bradfield (23) have noted that erroneous results were obtained where the quinhydrone electrode was used to determine the hydrogen-ion concentration of certain soils having a neutral or even an acid reaction. The presence in soils of comparatively large amounts of the higher oxides of manganese has been found to cause an error in the measurement of the hydrogen-ion concentration.…”