368 O. D. Allen on Caesium and Rubidium. 



seven parts of clilorid of calcium was next made ready; tlie two 

 mixtures were then united, and stirred vigorously during the 

 process of slaking, thus intimately blending the mineral with 

 suitable proportions of dry hydrate of lime, and chlorid of 



It was found by experiment that practically as good results 

 were obtained when the lepidolite was powdered sufficiently fine 

 to pass a sieve of 20 holes to the linear inch, as when it was 

 more finely pulverized, the fact being that the foliated struc- 

 ture of the mineral exposes a large surface to the decomposing 

 agency of the lime mixture. 



The mixture was heated to redness for six to eight hours in 

 hessian crucibles. Care was taken to avoid a heat much above 

 redness, as otherwise alkali-chlorids volatilize in dense clouds, 

 and the mass fusing, is absorbed to a considerable extent into the 

 crucible and lost. The long duration of the ignition was a mat- 

 ter of convenience, due to the character of the furnace employed, 

 and probably not necessary to the decomposition of the mineral. 



The agglomerated product obtained from the ignition of this 

 mixture was detached from the crucibles and boiled with water 

 a quarter to half an hour, and leached till all but a trace of the 

 chlorids was removed. The solution thus procured, containing 

 chlorid of calcium and the chlorids of the alkali-metals, was 

 evaporated till crystals began to form, then sulphuric acid was 

 added as long as sulphate of lime separated, taking care to avoid 

 an excess, and the whole mass was evaporated to dryness, and 

 strongly heated to expel free hydrochloric acid. The residue 

 was treated with water, and the small quantity of sulphate ot 

 lime which went into solution, was precipitated by carbonate of 

 ammonia, the filtered solution was again evaporated to dryness 

 and ignited. 



Ten and a half kilogrammes of lepidolite treated in this way 

 afforded 2169 grammes of salts consisting of chlorids, with a 

 small admixture of sulphates, of sodium, lithium, potassium, 

 rubidium and caesium. This quantity of salts subjected to Bun- 

 sen's process of fractional precipitation with bichlorid of plati- 

 num, furnished 132 grammes of the platinchlorids of caesium 

 and rubidium in which no potassium could be detected with the 

 spectroscope. The platinchlorids were very gently heated in a 

 current of hydrogen gas until complete reduction of the plati- 

 num took place, and the chlorids were then extracted with water. 



centages of caesium and rubidium obtained fro"^ \ 

 by this process were calculated from the amount of chio- 

 contained in these mixed chlorids. 



lineral 1 



