Comparison of glass and quinhydrone electrodes for determining the pH of some Iowa soils. II. The variability of results
1935
Dean, H.L. | Walker, R.H.
1. The variability of the results obtained by the use of the glass and quinhydrone electrodes for determining the pH of some Iowa soils was studied, and the nature and magnitude of the "QH error" and the "QH electrode error" were determined by means of the glass electrode. The potentials of the glass and quinhydrone electrodes were checked in a potassium acid phthalate buffer solution before and after the electrodes were suspended in a soil suspension for 20 minutes. 2. The variability in the pH of 25 samples of different soils, when determined by either the glass or the quinhydrone electrode, was comparatively small and presumably of little practical consequence. 3. The addition of quinhydrone to the soil suspension increased the pH of each soil slightly when determined by the glass or quinhydrone electrodes. This change in pH resulting from the addition of quinhydrone to the soil is referred to as the "QH error". This error was scarcely large enough to make the quinhydrone electrode method unreliable for determining the pH of the soils studied. 4. The glass and quinhydrone electrodes gave similar results when employed to determine the pH of soil suspensions containing quinhydrone. The "H electrode error", therefore, is of little or no consequence in the soils studied. 5. The potentials of the glass and quinhydrone electrodes change somewhat during the process of pH determinations. It is desirable, therefore, to check these electrodes against a known buffer solution at frequent intervals.
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