Abstract: A ternary complex of Nb with 5-Br-PADAP and tartrate ion has been investigated as a sensitive and selective system for the spectrophoto-metric determination of Nb.The molar ratio of the three components in the complex is estimated to be Nb: 5-Br-PADAP: Tar=1:1:1 and the possible structure of the mixed ligand complex is proposed.Anew method has been developed for the rapid determination of Nb in steels without separated Nb from its accompanying elements