pH is an abbreviation of “pondus hydrogenii” and was proposed by the Danish scientist S.P.L. Sørensen in 1909 in order to express the very small concentrations of hydrogen ions.

pH = - log Hydrogen ion concentration pH+pOH=14

0.001M=10exp-3=pH 3

0.01M=10exp-2=pH 2

0.1M=10exp-1=pH 1

1M=10exp0=pH 0

10M=10exp1=pH-1