1. n. [Drilling Fluids]
Hydrogen ion potential, which is the log10 of the reciprocal of hydrogen ion, H+, concentration. Mathematically, pH = log10 (1/[H+]), where [ ] represents mole/L. pH is derived from the ion-product constant of water, which at room temperature is 1 x 10-14 = [H+] x [OH-]. Pure water (at neutral pH) has equal concentrations of its two ions: [H+] = [OH-] = 10-7 mole/L. Log10 1/[H+] is 7, which is the pH of a neutral solution. The pH scale ranges from 0 to 14, and values below 7 are acidic and above 7 are basic.