A Study of Pyrogallol Derivatives of Thorium

Complex forming reaction of thorium with pyrogallol have been studied by potentiometric and preparative techniques. Equilibirum constants for the reactions:

                  \(Th^{4+} + C_6H_3(OH)_3\rightleftharpoons [Th(C_6H_3O_3)]^++3H^+\)

                  \(Th^{4+} + 2C_6H_3(OH)_3 \rightleftharpoons [Th(C_6H_4O_3)_2 + 4H^+\)

have been found to be 4.786 X 10^-7 and 5.035 X 10^-8 respectively. Sodium and potassium compounds, M₂[Th(C₆H₃O₃)₂]. 7H₂O, have been isolated.

Potentiometric titrations of thorium nitrate with KOH in presence of pyrogallol show a sharp inflec­tion at four equivalents of alkali per mole of thorium ion, indicating the possibility of an electrometric method for estimation of thorium.