Quantitative isolation:

A quantitative isolation of the element or compound is difficult -

This could be exemplified by the determination of iodide in a mixture of halides as its quantitative separation is almost impossible. ¹²⁸I (t_½ = 25 min) or 131I (t_½ = 8 d) may be used as a radiotracer which is formed by radioactive neutron capture of ¹²⁷I. Radiotracer with known specific activity could be added to the halides mixture or any other sample containing halides. All the halides may be precipitated by the excess addition of AgNO₃ solution. To the precipitate sulfuric acid and MnO₂ may be added which would oxidize I^- to I₂ which may be sublimed by heating and condensing vapours on a cold surface. The mass and activity of the condensed sample may be determined and thus the amount of I- or iodine may be determined.