Liquid-liquid equilibrium and tie line data in the system phosphoric acid/water/tri-n-butyl phosphate/calcium chloride has been determined at 298.15 K, in the concentration range from w = 0.028 to 0.20 phosphoric acid and w = 0 to 0.25 calcium chloride. Distribution coefficients of phosphoric acid and separation factors of water and calcium chloride were determined to establish the extracting capability of tri-n-butyl phosphate. The results show that tri-n-butyl phosphate can serve as an adequate extractant to recover phosphoric acid from dilute phosphoric acid containing calcium chloride.