Thorium Hydride, ThH₄

Thorium Hydride, ThH₄ was observed by Winkler that a heated mixture of thoria and magnesium absorbs hydrogen, and it was supposed that the greyish black product contained ThH₂. Matignon, however, obtained the hydride ThH₄ by the combination of the metal with hydrogen at a red heat. It is a solid not acted on by water but dissolved by hydrochloric acid with evolution of hydrogen, thus:

ThH₄ + 4HCl = ThCl₄ + 4H₂.

The formula was established by the measurement of the hydrogen evolved from a known weight of hydride. The hydride dissociates when heated, and at 390° C. dissociation is complete under atmospheric pressure.