On the interaction of vanadium (4) with derivatives 3,4,5-trihydroxy-isoxanthene

A study was made on interaction of vanadium (4) ions with dyes-pyrogallol red, brompyrogallol red and gallein- in the range of pH = 0-6. The maximal light absorption for gallein and brompyrogallol red is observed at pH=4 and λmax = 545 nm and 560 nm respectively. The compound of vanadium (4) with pyrogalloe red is characterized by the maximal light absorption at pH=5 and λmax=560 nm. Component ratio in all analyzed compounds is equal to 1:2. Molar extinction coefficients for compounds with gallein, pyrogallol red and brompyrogallol red are equal to 5000, 550 and 7400, and logarithms of stability constants - to 9.27, 13.17 and 13.25 respectively