Determination of thorium with organic reagents: different methods using p-aminosalicylic acid

p-Aminosalicylic acid (PAS) can be successfully utilized as a reagent for gravimetric and volumetric determination of thorium. A quantitative precipitate of thorium is obtained by adding a hot 2% solution of PAS, in the presence of a little ammonium acetate at a pH range between 4 and 5.6. The thorium salt filters, washes and ignites readily. Thorium content of the salt can be determined directly by ignition to thoria, and indirectly by the quantitative bromination of the organic ligand with bromide-bromate mixture or by iodination with iodine monochloride in glacial acetic acid solution at 0° C. The processes give comparable results.