O. D. Allen on Caesium and Rubidium. 369 



These numbers furnish the following equations : 

 (1) Rb-fCs=0-5825- 0-1439 



^ ' 85-36*^123-35* 35-5 

 which give Cs=0'3002 and Rb=01384 According to these pro- 

 portions the 132 grammes of platinchlorids contained 311969 

 grammes of caesium, 14-3826 grammes of rubidium, which 

 numbers respectively correspond to 0-3 per cent and 014 per 

 cent of the mineral employed. 



It appears therefore that it is practicable to extract almost one 

 half per cent of the two metals from the Hebron lepidolite, even 

 when operating on a large scale, and in a somewhat crude man- 

 ner, lu separating the platinchlorids of caesium and rubidium 

 from the platinchlorid of potassium, a not inconsiderable amount 

 of these metals went into solution with the potassium salt, thus 

 materially diminishing the quantity obtained. Much the larger 

 proportion of this loss was rubidium, due to the greater solubil- 

 ity of its platinchlorid. On comparing these results with Cooper's 

 analysesf of the Rozena lepidolite, it appears that although not 

 ^uite so rich in rubidium, the Hebron mineral is remarkably rich 

 in caesium. The lepidolite from Rozena and Zinnwald contain, 

 according to the published analyses, only an unweighable trace 

 of caesium, while that from Hebron contains more than three- 

 tenths of one per cent. 



Experiments in separating Caesium and Rvhidiam. — The process 

 described hj Bunsen for separating the new alkalies appeared to 

 be so troublesome, requiring for the preparation of pure rubi- 

 dium salts 20 to 30 extractions of the carbonates with boiling 

 absolute alcohol {Ann. Chem. u. Phar., cxxii, 353) that I have 

 niade various attempts to discover a simpler method. 



In the first place a trial was made with the picrates of the 

 tiew metals. To a concentrated solution of their mixed chlorids 

 an alcoholic solution of picric acid was added. The liquid im- 

 mediately filled with fine acicular crystals. These were rinsed 

 with water and successively recrystallized from fresh portions of 

 vrater eleven times. Portions of the 1st, 2d, 3d, 4th, 7th, and 

 llth crops of crystals were separately examined m the spectro- 

 scope, the picrates being converted into chlorids for this pur- 

 pose, by treatment with aqua regia. Ko difierence being ob- 

 servable between the spectra of the various crops, no further 

 experiments were made in this direction. It may be here re- 

 niarked that the mixed picrates crystallize with great facility m 

 needles an inch in length, and perfectly resemble the correspond- 

 ing potassium salt. 



I proportio 



f Jour.prakt. Chem., Ixxxv, 125. 



