The pH of a solution is a measure of its acidity or basicity, and is defined as the negative logarithm (base 10) of the hydrogen ion concentration ([H+]). Mathematically, it can be expressed as:

pH = -log10[H+]

- This definition involves using a pH meter, an instrument that measures the electrical potential generated by the difference in hydrogen ion concentration between a reference electrode and a glass electrode (the pH electrode).

- The glass electrode is sensitive to hydrogen ions, and the potential difference between the two electrodes is directly proportional to the logarithm of hydrogen ion concentration.

- To determine the pH of a solution, the pH meter is calibrated using standard solutions of known pH, and then the potential difference between the electrodes is measured when the pH electrode is immersed in the solution of interest.

- The measured potential difference is converted into a pH value using the calibration data.

For accurate pH measurements, it is essential to use properly calibrated pH meters and electrodes, employ appropriate techniques (such as temperature compensation), and follow standardized protocols to ensure accuracy and reliability.