Lanthanum is also used in Atomic Absorption spectroscopy to stabilise the signal of some elements. I think I used it quantifying Mg or Mn once, but never the less it stabilises some elements signals. It is also used in TIG welding, as well as Cerium and Thorium. These elements added in small concentrations to Tungsten electrodes, increase electron emission, among other factors. There are some interesting parallels between TIG welding and EM. ha!