Spectrophotometric study of vanadium(V)-phenylfluorone complex

Spectrophotometric studies of the reaction between vanadium(V) ions and phenylfluorone are presented and used for spectrophotometric determination of vanadium(V). The absorbance at 520 nm obeys Beer's law in the range of 2–15 μg vanadium/10 ml at pH 4. The relative standard deviation is 2% and the molar absorptivity based on vanadium is 2.1 × 10⁴ liters/mol cm. The composition of the complex in solution is of the 1:1 type with stability constant values to 2.5 × 10⁴. Analysis of the solid complex shows that its formula agrees with the formula (C₁₉ H₁₁ O₅)VO₂ · 5H₂O.