Analysis by Spectrum-observations. 347 



The salts of caesium and rubidium, as well as those of lithium 

 and strontium, have been likewise found in the water of the 

 "Wiesbaden springs, as also in that of the newly-bored artesian 

 well at Soden near Frankfurt. In order to obtain evidence of 

 the presence of the new alkalies in this water, it is only neces- 

 sary to boil out the platinum precipitate obtained from the 

 mother-liquor of 6 to 8 litres of the water; the caesium and 

 rubidium line3 are then easily recognized in the spectrum- 

 apparatus. 



We have examined small -quantities of the ashes of land -and 

 sea-plants, as well as Chili saltpetre and other alkaline salts 

 occurring in commerce, for the compounds of the new alkaline 

 metals, but we have not succeeded in detecting, in these sub- 

 stances, the presence of the salts of either metal. 



Having thus considered the occurrence and diffusion of caesium, 

 we pass on to the consideration of the methods of separation, by 

 means of which the compounds of this metal can be obtained in 

 a state of purity. If, as is almost always the case, potassium, 

 rubidium, and caesium occur together with sodium and lithium, 

 the first three metals can be separated from the two latter by 

 means of bichloride of platinum. The double chloride of plati- 

 num and potassium can be separated from the platinum compound 

 of the two new alkaline chlorides, as has been described, by 

 boiling the double salts out about twenty times with small quan- 

 tities of water; and thus the more soluble potassium-salt maybe 

 almost entirely removed. The double platinum compounds, 

 which now contain but traces of potassium-salts, are next heated 

 to redness in a current of hydrogen, at which temperature the 

 chlorides of caesium and rubidium do not fuse. The mass is then 

 treated with about seventy times its weight of water, and the alka- 

 line chlorides thus dissolved. The residual platinum is again 

 converted into chloride, which is diluted with water to the same 

 bulk as the solution of the alkaline chlorides ; both solutions are 

 then heated to boiling and mixed together. As soon as the pre- 

 cipitate which forms on mixing the solutions has collected in 

 sufficient quantity by the cooling of the liquid, it is thrown on 

 a filter, dried, and again subjected to the same treatment of reduc- 

 tion in hydrogen, &c, until a small portion brought into the spec- 

 trum-apparatus shows at most a faint trace of the potassium line 

 K«. The precipitate then contains solely the chlorides of caesium 

 and rubidium. For the purpose of separating these two bodies, 

 the solubility of the carbonate of caesium in absolute alcohol, and 

 the insolubility of carbonate of rubidium in the same liquid, is 

 made use of. 



The separation of the carbonate of caesium by repeated extrac- 

 tions with alcohol is, however, a difficult operation, as a double 

 2A2 



