Rubidium nitrate is a white crystalline powder that is highly soluble in water and very slightly soluble in acetone. In a flame test, RbNO3 gives a mauve/light purple colour.
RbNO3 can be prepared either by dissolving rubidium metal, its hydroxide or carbonate in nitric acid.
RbOH + HNO3 → RbNO3 + H2O
Rb2CO3 + 2 HNO3 → 2 RbNO3 + CO2 + H2O
2 Rb + 2 HNO3 → 2 RbNO3 + H2
References
^ abW. Lenk, H. Prinz, A. Steinmetz,"Rubidium and Rubidium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. doi:10.1002/14356007.a23_473.pub2