The atomic weight of caesium has been determined by the analysis of its chloride and bromide.
The platino-chlorides are reduced by hydrogen, and the caesium and rubidium chlorides extracted by water.
In order to separate caesium from rubidium, use is made of the different solubilities of their various salts.
The solubility of the various alums in water varies greatly, sodium alum being readily soluble in water, whilst caesium and rubidium alums are only sparingly soluble.
Caesium nitrate, CsNO 3, is obtained by dissolving the carbonate in nitric acid, and crystallizes in glittering prisms, which melt readily, and on heating evolve oxygen and leave a residue of caesium nitrite.
These sulphides are much less hygroscopic than the corresponding caesium compounds.
The separation of caesium from the minerals which contain it is an exceedingly difficult and laborious process.
Hackspill (Comptes Rendus, 5905, 141, p. 101) finds that metallic caesium can be obtained more readily by heating the chloride with metallic calcium.
The best source of rubidium salts is the residue left after extracting lithium salts from lepidolite, the method of separation being based on the different solubilities of the platino-chlorides of potassium, rubidium and caesium in water (R.
This residue consists of sodium, potassium and lithium chlorides, with small quantities of caesium and rubidium chlorides.