pH scale
n 1: (from potential of Hydrogen) the logarithm of the
reciprocal of hydrogen-ion concentration in gram atoms per
liter; provides a measure on a scale from 0 to 14 of the
acidity or alkalinity of a solution (where 7 is neutral and
greater than 7 is more basic and less than 7 is more
acidic); [syn: {pH}, {pH scale}]