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Rubidium bromide (RbBr) is a hygroscopic material, which is generally similar to the other rubidium halides.
Rubidium bromide is the bromide of rubidium. It has a NaCl crystal structure, with a lattice constant of 685 picometres.
There are several methods for synthesising rubidium bromide. One involves reacting rubidium hydroxide with hydrobromic acid:
RbOH + HBr → RbBr + H2O
Another method is to neutralize rubidium carbonate with hydrobromic acid:
Rb2CO3 + 2 HBr → 2 RbBr + H2O + CO2
Rubidium metal would react directly with bromine to form RbBr, but this is not a sensible production method, since rubidium metal is substantially more expensive than the carbonate or hydroxide; moreover, the reaction would be explosive.

white crystalline powder

Rubidium bromide is used in infrared optics.

The bromide is a white crystalline powder which crystallises from H2O (solubility: 50% in cold and 67% in boiling H2O to give a neutral solution). It also crystallises from near-boiling water (0.5mL/g) by cooling to 0o.