Spectrophotometric Determination of Cerium(III) and Some Rare Earths with Xylenol Orange

A method has been described for the spectrophotometric determination of 20 to 100μg. of a rare earth element using xylenol orange. The complexes of cerium(III), lanthanum-(III), neodymium(III) and yttrium(III) with xylenol orange have an absorption maximum at 575 to 578μ vs. the reagent blank. Each of them is a 1 : 1 complex and has a formation constant of approximately 105 under the conditions studied. Anions such as NTA and EDTA inhibit the color development of the complexes.