Thorium

Gas Lamps

Thorium found its first significant application in gas lamps in 1885. These gas mantles, made of mesh cloth bags impregnated with thorium oxide, would glow brightly when heated with a gas flame. However, due to health concerns, thorium has been phased out from gas mantles over the last 30 years and replaced by safer materials like yttrium 1.

When the gas mantles were lit, the cloth part would burn away, leaving a very fragile mesh of thorium oxide, which would glow brightly.

--- Gary Arndt

This phase-out has led to a significant reduction in the industrial and commercial use of thorium 1.

   

Radioactivity

The discovery of thorium's radioactive properties was a pivotal moment in science. In 1898, both Gerhard Karl Schmidt and Marie Curie identified thorium as radioactive, making it the second element known to possess this property after uranium 1. This discovery was crucial in understanding the nature of radioactivity and the decay of elements.

It was the study of thorium which led to the discovery of half lives and solidified the theory that radiation was the decay of elements.

--- Gary Arndt

Thorium's weak radioactivity and its long half-life of 14.05 billion years further underscored its unique characteristics 1.