The hydrogen ion concentration of a solution is measured by the value.

The concentration of hydrogen ions in a solution is measured by the pH value. The pH scale ranges from 0 to 14. A pH of 7 is neutral, meaning the concentration of hydrogen ions and hydroxide ions are equal. If the pH is less than 7, the solution is acidic, meaning it has a higher concentration of hydrogen ions. If the pH is greater than 7, the solution is basic or alkaline, meaning it has a lower concentration of hydrogen ions. The pH scale is logarithmic, so each change of 1 pH unit represents a tenfold change in the concentration of hydrogen ions.