190 Mr. 0. D. Allen on Ccesium and Rubidium, 



Lepidolite occurs at Hebron in large quantity, in a coarsely 

 crystalline granite, associated with red and green tourmaline 

 and albite. It has a granular and at the same time foliated 

 crystalline structure, a pale rose to violet colour, and very closely 

 resembles the lepidolite of Penig in Saxony, and, like that, is also 

 associated with the rare species amblygonite. 



Preparation of the salts of Ccesium and Rubidium from the 

 Hebron Lepidolite. — The process used for decomposing this 

 mineral was based upon that employed by Prof. J. Lawrence 

 Smith for the determination of alkalies in silicates. Ten parts 

 of the pulverized lepidolite were first mixed with forty parts of 

 coarsely powdered quicklime; a mixture of enough water to 

 slake the quicklime, with hydrochloric acid sufficient to form 

 from six to seven parts of chloride of calcium, was next made 

 ready; the 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 

 chloride of calcium. 



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 structure 

 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 the alkaline chlorides 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 matter 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 

 till all but a trace of the chlorides was removed. The solution 

 thus procured, containing chloride of calcium and the chlorides 

 of the alkali-metals, was evaporated till crystals began to form ; 

 then sulphuric acid was added as long as sulphate of lime sepa- 

 rated, taking care to avoid an excess, and the whole mass was 

 evaporated to dryness, and strongly heated to expel free hydro- 

 chloric acid. The residue was treated with water, and the small 

 quantity of sulphate of lime which passed into solution was pre- 

 cipitated 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 chlorides, with a 



