Abstract: In a process for purifying an aqueous phosphoric acid containing up to about 55% P.sub.2 O.sub.5 by weight and dissolved magnesium, iron and aluminum ions, wherein (a) said phosphoric acid is contacted with an organic extractant containing a water immiscible organic sulfonic acid to form: a loaded organic extractant phase containing the organic sulfonic acid, extracted ionic metallic impurities and extracted P.sub.2 O.sub.5 values, and a purified aqueous phosphoric acid; (b) the purified aqueous phosphoric acid phase is separated from the loaded organic extractant phase; (c) the separated loaded organic extractant phase is contacted with a solution phase containing calcium ions (e.g., calcium nitrate), under conditions whereby at least some of said extracted ionic metallic impurities (e.g., Mg.sup.+2, Al.sup.+3, Fe.sup.