1. n. [Drilling Fluids]
A chemical analysis to measure the hardness ions in water-mud filtrates or in make-up water. Hardness is quantitatively determined by titration using standardized EDTA (versenate) reagent and ammonium hydroxide (weak) buffer, typically according to procedures of API. Results are reported as calcium ion in mg/L. The hardness ion Ca+2 can be analyzed alone by another EDTA titration method described by the API.