The Spectrophotometric Determination of Cerium Sub-Group Rare Earth Elements in Ferro-and Nickel-Base Alloys with Chlorophosphonazo-m-NO_2

A method for the speotrophotometrio determination of cerium subgroup elements in ferro-and nickel-base alloys with chlorophosphonazo-m-NO_2 is described.Yttrium subgroup elements can be effectively masked by oxalic acid in acid medium.Under the experimental conditions employed,in the presence of the corresponding amounts of iron、nickel and nickel-chromium in the samples,the apparent molar absorptivities of cerium at 666 nm are found to be 8. 7×10~4. 8. 6×10~4 and 9. 3×10~4 1·mol~(-1) ·cm~(-1) respectively;Beer's law is obeyed for 0～12、 0～10 and 0～10μg of cerium(Ⅲ)respectively in 25 ml of solution at 666 nm.10μg of cerium can be determined in the presence of 5-fold amounts of yttrium sub-group elements.The percentage of recovery of cerium is 96～105. The coefficients of variation for cerium (0. 025%) in forte-base alloy、(0. 022%) in nickel-silicon alloy、(0. 021%) in nickel-chromium alloy (10 determinations each) are 1. 7%,0. 74% and 0. 46% respectively.The present method is sensitive and selective,satisfactory results can be obtained in the determinations of micro amounts of cerium.