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Digital pH measurement. Student using a digital pH meter to measure the pH of a chemical solution. The tip of the probe is immersed in the liquid, which is weakly acidic. The probe's tip contains electrodes that measure the electrical potential of the hydrogen ions. This is directly related to pH, which is a measure of the concentration of hydrogen ions. A pH reading below 7 is acidic, one above 7 is alkaline, while a pH of 7 is neutral.
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