ABSTRACT
A mixed-ligand complex of vanadium(V) with N-benzohydroxamic acid and thiocyanate formed at various acidities can be extracted into methyl isobutyl ketone, and used for photometric determination of trace amounts of vanadium in materials such as alloy steels and rocks. The absorption maximum of the violet mixed-ligand complex is at 535 nm. The values for the simple complex are 505 nm and molar absorptivity 7.4 x 10(3)l.mole(-1).cm(-1).
ABSTRACT
Highly sensitive methods for the determination of lan thanum, thorium and iron(III) have been developed with the sodium salts of 2-(pyridyl-2-azo)chromotropic acid, 2-(pyridyl-3-azo)chromotropic acid and 2-(2-carboxypyridyl-3-azo)chromotropic acid. Optimum concentration ranges are of the order 1-20 ppm. The effect of diverse ions (cations and anions) including those of rare-earths are reported. The nature of the complexes has been investigated and values for the instability constants are given.
ABSTRACT
Pyridyl-2-azo-chromotropic acid (disodium salt) is proposed as a new reagent for the determination of nickel and cobalt in the presence of many ions and for their simultaneous determination in the absence of cyanide and EDTA. The wavelengths of maximum absorption for the nickel and cobalt complexes are 570 and 640 mmu respectively. Beer's law is obeyed by the complex systems from 0.125-0.8 ppm of nickel and 0.16-1.2 ppm of cobalt. The optimum concentration ranges are 0.25-0.8 ppm for nickel and 0.16-1.2 ppm for cobalt and the relative error is 2.7 %. The molar absorptivities for the complexes of nickel and cobalt are 40,720 and 33,600, while the dissociation constants at pH 7.5 and 22 degrees are of the order of 10(-12) and 10(-13), respectively. The metal to reagent ratio is 1:3.
