A measure of the acidity or alkalinity of a solution based on its hydrogen ion (H⁺) concentration. The pH of a solution is the negative logarithm (base 10) of its H⁺ concentration. Since the scale is logarithmic, there is a tenfold difference in hydrogen ion concentration for each pH unit. The pH scale ranges from 0 to 14 with 7 indicating neutrality ((H⁺)= (OH^-)). Values above 7 indicate progressively greater alkalinity, while values below 7 indicate progressively increasing acidity.

pH scale. (McGraw-Hill Inc. Reproduced by permission.)

See Also

Acid and Base; Buffer