Rubidium hydrogensulfate, sometimes referred to as rubidium bisulfate, is the half neutralized rubidium salt of sulfuric acid. It has the formula RbHSO4.
Properties It is a hygroscopic compound.
Its crystals are isomorphs with ammonium hydrogensulfate crystals.
Its enthalpy of solution is 15.62 kJ/mol.M. de Forcrand: "Sur les chlorures et sulfates de rubidium et de caesium" in Compt. Rend. Hebd. 1906, 143, S. 98. Volltext
After warming up it decomposes to rubidium disulfate and water:R. Abegg, F. Auerbach: "Handbuch der anorganischen Chemie". Verlag S. Hirzel, Bd. 2, 1908. S. 432.Volltext
Synthesis It may be synthesised with water and a stoichiometric amount of rubidium disulfate. Reaction takes place where there is no humidity:S. B. Rasmussen, H. Hamma, K. M. Eriksen, G. Hatem, M. Gaune-Escard, R. Fehrmann: "Physico-chemical properties and transition metal complex formation in alkali pyrosulfate and hydrogen sulfate melts". VII International Conference on Molten Slags Fluxes and Salts, The South African Institute of Mining and Metallurgy, 2004. Volltext (PDF; 661 kB)
There is another method of creation. It is similar to the synthesis of sodium sulfate and potassium sulfate. This reaction requires rubidium chloride and a little bit of warm sulfuric acid. Some hydrogen chloride is also produced during the reaction.
Related compounds
Like potassium and caesium, rubidium has another hydrogensulfate compound as well: Rb3H(SO4)2.
References