It is based on the reaction between Evans blue and KBrO3 is catalysed by vanadium in hot dilute H2SO4 solution and in the presence of ascorbic acid and the diminution in absorbance of the system permits vanadium to be determined.

• 它基于在热的稀H_2SO_4溶液中,有抗坏血酸存在时,依文思蓝与KBrO_3反应受钒的催化且吸光度降低与钒量相关。