Xylenol orange is a very important developer in mieroanalysis. Pb^2＋ Can react with XO to form a stable 1 ： 1 complex of red color in Britton-Robinson buffer of pH 6.0. Chromogenic reaction of Pb^2＋ -xylenol orange system was studied and a new spectrophotometric method for determining trace lead was established. The results showed that the maximum absorption wavelength is 580 nm. The apparent molar absorption coefficient is 3. 312 × 10^4 L/（ mol · cm）. As the Pb^2＋ concentration is in the range of 0. 075 × 1.2 mg/L, it follows the Beer...
