The precipitation of thorium with certain organic reagents has been shown to afford a basis for polarographic methods for the determination of thorium. Appropriate conditions for the precipitation of thorium by certain reagents have been determined, and the advantages of a homogeneous precipitation of thorium 8-quitnolinate have been demonstrated. The precipitate that thorium forms with m-nitrobenzoic acid has been found to be the tetra-m-nitrobenzoate. The new polarographic methods tor thorium have been proven to be directly applicable to zirconium-free magnesium-base alloys . When zirconium is present, a simple anion exchange procedure will eliminate the interference of zirconium, and allow it's subsequent determination.The satisfactory nature of the precision and accuracy of the proposed methods, and their applicability to substances other than magnesium-base alloys, have been demonstrated. / Thesis / Master of Science (MS)