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 × 10^–14 = [H⁺] × [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.

See: alkaline,  alkalinity,  alkalinity test,  bland coring fluid,  bromocresol green,  buffer,  buffer solution,  buffered mud,  buffered solution,  calcium sulfate,  carbon dioxide,  carbonate ion,  completion fluid,  hydrogen sulfide,  hydrolysis,  pH test,  phenolphthalein,  phosphate salt,  prehydrated bentonite,  quebracho,  red mud,  salt,  SAPP,  siderite,  silicate mud,  sodium bicarbonate,  sodium carbonate,  wastewater cleanup