A Simple Method to Measure pH Accurately in Acid Rain Samples

Abstract

Conventional pH electrodes, which are designed to function in high-conductivity solutions, show slow and erratic response in pure water samples such as acid precipitation. Increasing conductivity without shifting pH solves the measurement problem. This method correctly measures pH in low conductivity solutions, using a Ross combination pH electrode, after the addition of a small amount of potassium chloride (KCl) solution to the sample. The Ross electrode, with its unique internal redox system, is chosen since it eliminates problems associated with temperature and because the precision and accuracy of data obtained in preliminary testing with it were comparable to those obtained with the standard hydrogen electrode. KCl addition to samples does not alter the pH significantly.

Effect of storm type on rainwater composition in southeastern North Carolina

“…Figure 7 illustrates a pH dependence in accordance with that predicted. The values of the log *K values obtained experimentally are comparable with those observed for other carboxylic acids; e.g., Kummert and Stumm report a value for benzoic acid of log SK = 3.7 (11).…”

“…This procedure may yield slightly low results for rain samples that have pH above 5 (9). Beginning in the autumn of 1985, rainwater pH was also analyzed with a Ross electrode calibrated with two Orion low ionic strength buffers and with the addition of pHix (Orion) to samples to avoid liquid junction potentials, which result from the different ionic strengths of buffers and samples (10,11). In this analysis, all solutions were stirred.…”

Redox Speciation of Copper in Rainwater: Temporal Variability and Atmospheric Deposition

“…Inorganic ions (Cl -, NO3 -, and SO4 2-) were analyzed using suppressed ion chromatography (32,33). Analysis of pH was conducted using a Ross electrode with low ionic strength buffers (34,35). Fe(II) and Fe(III) were analyzed using ferrozine (36) and long path length absorbance spectroscopy (LPAS) with a 1 or 5 m cell (37).…”

Chromium Speciation in Rainwater: Temporal Variability and Atmospheric Deposition

“…Rain samples were also analyzed for Cl - , NO 3 - , and SO 4 2- using ion suppressed chromatography ( , ). Analysis of pH was conducted using a Ross electrode with low ionic strength buffers ( , ). Iron(II) and Fe(III) (by difference after reduction) were analyzed using the ferrozine method () using LPAS with a 5-m cell.…”