Rubidium hydride, RbH

The Rubidium hydride, RbH, has been prepared by a method analogous to that employed for sodium hydride. It can also be produced by heating rubidium carbonate with metallic magnesium in an atmosphere of hydrogen at 650° C. for five days. It is a white, crystalline substance, with density about 2. The vapour-tension for each temperature-interval of 10° between 350° and 450° C. corresponds with the values 100, 114, 130, 160, 200, 253, 322, 424, and 567 mm. respectively. A possible source of error may be the presence of carbon dioxide as the result of decomposition of the magnesium carbonate formed; but soda-lime was employed to absorb any carbon dioxide liberated, and the measurements were made rapidly. The tension increases rapidly to 85 mm. at 230° C., and then slowly to 100 mm. at 370° C.

This hydride is more stable than that of caesium, but less stable than that of sodium or of potassium. It is very reactive. When heated in vacuum at 300° C. it decomposes into its constituent elements. At ordinary temperatures it is attacked by the halogens. Carbon dioxide converts it into rubidium formate:

RbH+CO₂=HCOORb.

Under reduced pressure sulphur dioxide converts it into rubidium hyposulphite, Rb₂S₂O₄.