界面活性剤共存下における1-(2-ピリジルアゾ)-2-ナフトール又はその銅キレートを用いる銅及びニッケルのEDTA滴定

概要

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1-(2-Pyridylazo)-2-naphthol (PAN) reacts with Cu^<2+> over the wide pH range. A 1:1 (metal-to-ligand ratio) chelate with an absorption maximum at 555 nm is formed in acidic solution, and a 1 : 2 chelate (abs. max. 558 nm) in alkaline solution. Both chelates are insoluble in water, but can be solubilized in the presence of non-ionic surfactants. EDTA titrations of metals with PAN and Cu-PAN indicators are therefore facilitated with them. The optimum conditions for such titrations, and especially the rate of color change in the course of the titration of Cu^<2+> with PAN, were studied. The rate (obtained with the assumption of a pseudo-first order law) is increased by the surfactants such as Triton X-100 and Brij 35 all over the course of titration, and the addition of dioxane is effective only near the end point. In the presence of Triton X-100 surfactant, Pb^<2+> can be titrated with Cu-PAN indicator at pH 3.4〜4.3 twice as quickly as in the absence, Ni^<2+> can be titrated at pH 3.5 with a very sharp end point in the presence of Brij 35 at 80℃, where Triton X-100 was ineffective because of its low cloud point.
社団法人日本分析化学会の論文
1980-04-05