The Spectro photometric Determination of Cerium Sub-group Rare Earth Elements in Aluminiun Base Alloy with Chlorophosphonazo-m-NO_2

Chlorophosphonazo-m-NO_2(CPAmN) is one of the Bisazo Chlorosphonazo derivativesof unsymmetrical chromotropic acid, its structural formula is described as follows: CPAmN is a deop red crystal which is dissolved in water. In acidic media, CPAmNis bright red and reacts with rare-earth ions to form blue or green complexes. In thepresence of excess of the reagent, Cerium (111)reacts with CPAmN to form 1: 3 complex. The experimental determinations of cerium sub group rare earth elements in alum-inium-base alloy with CPAmN are described. Yttrium sub-group elements can beeffectively masked by oxalic acid in acidic medium. Under experimental conditionsemployed, the apparent molar absorptivities of cerium and lanthanum at 660 nm arefound to be 7.6×10~4 and 7.8×10~4 1·mol~(-1)·cm~(-1) respectively. Sandell sensitivities arefound to be 0.0184μg ce·cm~(-2) and 0.00178μg La cm~(-2). Beer's law is obeyed for 0～12μg of Ce and 0～10μg of La in 25 ml of solution. 10μg cerium can be determined inthe presence of 5-fold amounts of yttrium sub-group rare earth elements. The coefficientsof variation for the determination of 10.0μg of cerium and 10.0μg of lanthanum(10determinations each) are 0 .82% and 0.68% respectively. The percentage of recoveryof cerium is 95～105. The present method is sensitive and selective, satisfactory resultscan be obtained in the determinations of micro amounts of cerium in the aluminum-base alloy.