Effects of temperature, filtration and container material on storage of an acid stream water

Abstract

Precise measurements of the pH of an acid stream water (pH 4.8, 4 °C) have been made on filtered and unfiltered samples stored at three different temperatures over 15 d. Sub-samples stored in glass bottles had a significantly lower pH, by 0.02, than those stored in polythene bottles, presumably due to outgassing of CO₂. Filtration did not affect the pH, but storage in glass bottles for 15 d introduced a variation of ±0.1 pH. Whereas the pH of samples stored at 10 and 20 °C did not change over a 2-week period, storage at 4 °C caused the pH to increase by 0.1. The temperature dependence of the pH could be predicted by assuming that it was controlled by the hydrolysis of aluminium, for which enthalpy data are available.