2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚与铅(Ⅱ)、锌(Ⅱ)络合平衡的双系列线性回归法研究

Complexation Equilibrium of 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol With Lead and Zinc by Dual-series Linear Regression Method

本文用双系列线性回归法研究了Pb(Ⅱ)、Zn(Ⅱ)与5-Br-PADAP的络合反应,发现在pH5～6.5,30％乙醇溶液中,Pb(Ⅱ)与5-Br-PADAP形成1:1络合物,Zn(Ⅱ)主要形成1:2络合物,两种络合物的稳定常数(lgβ)分别为11.17、22.31,最大吸收波长分别为575、550nm,摩尔吸光系数分别为6.01×10~4、1.34×10~5L·mol^(-1)·cm^(-1)。

Abstract A new spectrophotometric method, dual-series linear regression method, has been used to study the complexation equilibrium of 2-(5-bromo-2-pyridylazo)-5-diethyl-aminophenol(5-Br-PADAP) with Pb( Ⅱ ) and Zn( Ⅱ ) in at containing 30% (V/V)ethanol solution at pH 5-6. 5. In the usual experimental conditions, Pb( Ⅱ ) and Zn( Ⅱ ) react with 5-Br-PADAP to form 1 : 1 and 1 : 2 complexes, respectively. The maximum absorption wavelengths of the two complexes are 575 and 550 nm, the molar absorptivities are ε_pbl=6. 01×10~4 and ε_(znL)_2=l.34×10~5L ·mol^(-1) ·cm(-1) ,respectively. After considering the pH effect in 5-Br-PADAP complexing, their stability constants are lg/β_(pbl)_2 = 11.17 and lgβ_(znL)_2 = 22. 31, respectively.