Reported experimental data on aqueous solubility of Tri-n-Butyl Phosphate (TBP) in 5-100% TBP/n-dodecane-nitric acid-water biphasic system at 298.2 K was analyzed by least-squares technique and an extended Setschenow model was proposed for correlating the same. Database could be correlated with a standard deviation of about 7%. A further extension was proposed for presence of multiple solutes (extracting/non-extracting).