pH

pH [pē΄āch′]

n.

[< Fr p(ouvoir) h(ydrogène), lit., hydrogen power]

the degree of acidity or alkalinity of a solution; it is the logarithm of the reciprocal of the hydrogen-ion concentration in gram equivalents per liter of solution (Ex.0000001 gram atom of hydrogen ion per liter yields a numeric reciprocal of ten million, the log of ten million equals 7, therefore 7 is the pH): a pH of 7, the value for pure distilled water, is regarded as neutral; pH values from 7 to 0 indicate increasing acidity and from 7 to 14 indicate increasing alkalinity