In general, hydrogen itself (and compounds containing hydrogen)
when oxidised by heating with oxygen or with a metal oxide form
water, for which tests are available. There are otherwise no chemical
tests for hydrogen. The metal palladium will take up many times its
own volume of hydrogen, to form a non-stoichiometric metal
hydride (p. 113) and this property can be used to separate hydrogen
from other gases which remain unaffected by the palladium.