Pyrogallol azo derivatives as analytical reagents for determining nickel(II)

Reagents based on bis-(2,3,4-trihydroxyphenylazo)benzidine and 2,2′,3,4-tetrahydroxy-3′-sulfo-5′-nitroazobenzene were used for the spectrophotometric determination of nickel. The optimum complexation conditions were found and the stability constants of the nickel complexes were determined. The effect of foreign ions and masking substances on the complexation was studied. The procedure was used for the photometric determination of nickel in volcanogenic rocks.