PH
A measure of the acidity or alkalinity of a fluid.
The pH of any fluid is the measure of its hydrogen ion (H<SUP>+</SUP>) concentration relative to that of a given standard solution.
The pH may range from 0 to 14, where 0 is most acid, 14 most basic, and 7 is neutral.
Mathematically, the pH is the logarithm (to the base 10) of the reciprocal of the hydrogen ion concentration, [H+].
The pH is approximately equal to the negative logarithm of the H+ ion concentration expressed in molarity.