A quantitative spectrographic method has been developed for the determination of eight impurity elements in indium within the range 0.0005-0.1%. The elements chosen are those considered to be of most probable occurrence and importance and are as follows; copper, gallium, iron, lead, nickel, silver, tin and zinc. The analytical method utilizes a high-voltage a.c arc excitation on a platform-centerpost electrode coated with dried sample salts. The method is versatile in that it can be extended to include higher, lower or other impurity element concentrations of interest. An over-all accuracy of approximately ±15% of the amount found can be expected.
H. M. Hyman, "Spectrographic Analysis of Indium Metal for Impurities," Appl. Spectrosc. 14, 125-127 (1960)