Originally introduced in 1909 by S. P. L. Sørensen, using the notation pH+ for what he called the “hydrogen ion exponent” (Wasserstoffionenexponent ) of a solution. He may have chosen the symbol p arbitrarily; another suggestion is that it abbreviates German Potenz (“power”). The “H” is the international chemical symbol for the element hydrogen.
- (chemistry) Measure of the acidity or basicity of an aqueous solution, equal to the negative logarithm of the concentration of hydronium ions in molars
- (metrology) Symbol for picohenry, an SI unit of electrical inductance equal to 10−12 henrys.