C 498 ] 



LXIV. Chemical Analysis by Spectrum-observations. 



By G. Kirchhoff and R. Bunsen. 



[With a Chromolithograph Plate.] 



[Continued from p. 349.] 



IV. On Metallic Caesium and some of its Compounds. 



a. Metallic Caesium. 



IF fused chloride of csesium be placed in the circuit of a pow- 

 erful zinc-carbon battery, exactly the same phenomena are 

 noticed as when the chlorides of potassium or rubidium are thus 

 treated. 



The amalgam of caesium is, however, not so easily formed from 

 an aqueous solution of the chloride as is the rubidium-amalgam 

 under similar circumstances. It can be obtained in a solid cry- 

 stalline form only by the aid of a very powerful current. When 

 thus prepared it is of a silver-white colour, exhibiting a granular 

 structure. It undergoes oxidation on exposure to air much more 

 rapidly than rubidium-amalgam, and quickly decomposes water. 

 With a solution of chloride of potassium, it is found to be posi- 

 tively electric when compared with the amalgams of sodium, 

 potassium, and rubidium ; so that caesium must be considered as 

 the most electro-positive of all the known elementary bodies. 



b. Hydrated Oxide of Caesium. 



The properties of fused chloride of csesium, when acting as an 

 electrolyte, show plainly that, like potassium, this metal forms 

 a suboxide. We have not yet examined the compounds formed 

 by csesium with more than one atom of oxygen ; the analogy of 

 the metal with potassium would, however, render the existence 

 of such compounds probable. The hydrated oxide, which is pre- 

 pared in a similar manner to the corresponding rubidium com- 

 pound, resembles the latter in all its properties. It contains one 

 atom of water, which cannot be expelled by heat; it is in a high 

 degree deliquescent, becomes strongly heated in contact with 

 water, and is at least as powerful a caustic as potash or hydrated 

 oxide of rubidium. It dissolves easily in alcohol, forming a 

 syrupy liquid. 



c. Monocarbonate of Ccesium. 



Like the corresponding rubidium compound, this salt is most 

 easily obtained by decomposing the boiling solution of the sul- 

 phate of cEPsium with baryta-water, evaporating the caustic liquor 

 to dryness with carbonate of ammonium, and separating any in- 

 soluble carbonate of barium by nitration. From the syrupy 

 solution of the carbonate, the hydrated salt crystallizes in irre- 

 gular masses, which soon deliquesce on exposure. The crystals, 

 on heating, fuse in their water of crystallization, leaving a residue 



