SPECTROPHOTOMETRIC METHODS USED IN THE INVESTIGATION OF SEVERAL COMPLEXES IN SOLUTIONS

Some complexes are investigated in solution by spectrophotometric methods, using a Coleman Universal Spectrophotometer, Model 14. I Chelate formation between iron(III) and acetoacetanilide (AAA) has been studied using the continuous variation, spectrophotometric titration and straight-line methods. The chelate has a violet colour and is stable between pH 2.3-3.2. The chelate has a maximum absorption at 560 mμ and the composition corresponds to one of a metal ion per one chelating molecule. The stability has been calculated by 4 methods and the average value of the dissociation constant is Kc ≈ 4 × 10-3. The molar absorption coefficient at λ = 560 mμ is 1234. The complex was found to obey Beer's law in the concentration range 1–80 mμ of Fe3+/ml. and AAA may be employed as a reagent for the colorimetric determination of iron(III). Other common metallic ions do not interfere. II Chelate formation between cupric ions and NAH and INA has been studied using the continuous variation, spectrophotometric titration and straight-line methods. The nature of these complexes is discussed and it is concluded that the composition corresponds to one of metal ion per two chelating molecules. The chelate Cu(INA)2 has a green colour and is stable for over 12hr. It is undoubtedly a very promising reagent for cupric ions. The chelate has a maximum absorption at 680–720 mμ. The stability has been calculated and the average value is Kc ≈ 1.64 × 10-5.