What is the important uses for thallium?

Answer 1

Thallium is used to toughen welding arc points.

Edit: Although I know from a strong manufacturing background in aerospace, including special processes such as welding tough to weld metals, that thallium was used in welding electrodes I find no reference to this during a post search. I withdraw the answer.

Edit 2: Sometimes I can not help myself. Further research points out that it is thorium that is used in welding electrodes, not thallium.

Answer 2

Thallium is used in certain medical imaging tests to help visualize certain organs and tissues in the body. It is also used in electronic devices, like infrared detectors and semiconductors. Additionally, thallium is sometimes used in the production of glass and ceramics.