Sensitive flotation-spectrophotometric method for the determination of vanadium (IV) with 3,5-dinitrosalicylic acid and rhodamine B

Vanadium(IV) is determined by reaction with 3,5-dinitrosalicylic acid and rhodamine B in weakly acidic medium. The flotation of the ternary ion-association complex is carried out with cyclohexane followed by dissolution in acetone for subsequent spectrophotometric determination. The molar absorptivity is 5.91×10⁵ l mole^–1 cm^–1 at 555 nm. Beer's law is obeyed in the range 0.05–1.5 g vanadium(IV) in 25 ml. The method is selective for vanadium(IV) in the presence of sodium fluoride and has been applied to standard reference materials.