Trace characterisation of tin-bismuth alloy by optical emission spectrography

An emission spectrographic method has been developed for the determination of eighteen impurities in a tin-bismuth alloy sample. The metal alloy is converted to its oxide form and mixed with pure graphite in the ratio 2:1. 20mg of this mixture taken in a 1/4inch dia graphite electrode, is excited in nitrogen atmosphere using a 10 amp d.c. arc. The spectra of the samples are photographed using a 3.4M Ebert spectrograph with a 1180 grooves/mm grating. The concentration range covered are between 0.1ppm and 1000ppm for various elements and the precision of the method is found to be about 18 per cent. (author). 4 tabs., 6 figs