Synthesis of 1-Azobenzene-3-(5-Chloro-2-Pyridyl)-Triazene and Its Color Reaction with Nickel

azobenzene-3-(5-chloro-2-pyridyl)-triazene (A BC PDT) as a chromogenic reagent was synthesized and its color reaction with nicke l was investigated. In the buffer solution of Na 2B 4O 7-NaOH (p H 10.5) and with the existence of surface active agent of OP,1-azobenzene-3- (5-chloro-2-pyridyl)-triazene reacts with nickel to form a red complex with molar ratio of Ni 2+∶ABCPDT=1∶3. The absorption maximum o f the complex lies at 540 nm with an apparent molar absorptivity of 1.62×10 5 L·mol -1·cm -1. The Beer′s law is well obeyed in the range of 0～480 μg/L of nickel. The method has been applied to the direct determination of nickel in alloy with satisfactory results and precision of less than 2% RSD (n=6).