The only available source of water for the drilling fluid has a [Ca2+ 1 of 900 ppm and a [Mg+1 of 400 ppm. Determine the con- centration of caustic and soda ash that would be required to remove the Ca2+ and Mg2+ by precipitation, Would any other undesirable ions still be present? Answer: 0.46 lbm/bbl of NaOH and 0.84 lbm/bbl of Na, CO2. Yes, NaCl.