Aluminium chelates with pyridyl azo dyes of chromotropic acid and their applications in microanalysis

Abstract

Aluminium forms complexes with 2-(pyridyl-3-azo)-chromotropio acid (Na-salt) (Reagent B) and 2-(2-oarboxy pyridyl-3-azo)-chromotropic acid (Na-salt) (Reagent C) at pH 5.0, having maximum absorption at 580 nm. The system with Reagent B obeys Beer's law from 0.5 to 3.5 p. p. m. with optimum concentration range from 0.5 to 2.5 p. p. m., while with Reagent C Beer's law is obeyed from 0.2 to 2.2 p. p. m. and the optimum range is from 0.2 to 2.0 p. p. m. of aluminium. The percent relative errors are 2.71 and 2.72, respectively. The determination of composition by continued variation, molar ratio and slope ratio methods suggests a metal to reagent ratio of 1∶3 for Al-Reagent B complex and a 1∶1 ratio for Al-Reagent C complex; the dissociation constants of these complexes being, respectively, of the order of 10−13 and 10−5. The molar extinction coefficients are 5946 and 9747 while the sensitivities calculated are 0.00453μg/cm2 Al and 0.00276μg/cm2 Al, respectively.