The organo-arsenic compound, cacodyls, was formed 
The organo-arsenic compound, cacodyls, was formed by this man as the most  complex radical of the sort at the time. His collaboration with Kirchoff led to the  discovery of many new elements by their spectrograph. His pupil, Auer von  Welsbach [VELZ-bock], employed his teacher's namesake instrument in working  with rare earth oxides to produce light. FTP, name this chemist whose burner heats  many experiments.
The organo-arsenic compound, cacodyls, was formed by this man as the most  complex radical of the sort at the time.